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Columbia ®[nt&ersttp Hectures

THE DOCTRINE OF EVOLUTION

THE HEWITT LECTURES
1906-1907

COLUMBIA

UNIVERSITY PRESS

SALES AGENTS

NEW TORK:

LEMCKE & BUECHNER

80-32 West 27th Steebt

LONDON :

HENRY FROWDE

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TOEONTO :

HENRY FROWDE

25 EiCHMOND St., W.

COLUMBIA UNIVERSITY LECTURES

^

THE DOCTRINE OF EVOLUTION

ITS BASIS AND ITS SCOPE

BY

HENRY EDWARD CRAMPTON, Ph.D.

PROFESSOR OF ZOOLOGY, COLUMBIA UNIVERSITY

NehJ gork
THE COLUMBIA UNIVERSITY PRESS

1911

All rights reserved

COPTBIGHT, 1911,

Bt the COLUMBIA UNIVEESITT PRESS.

Set up and clectrotyped. Published June, 191 1.

J. S. Gushing Co. — Berwick & Smith Co.
Norwood, Mass., U.S.A.

PREFACE

The present volume consists of a series of eight
addresses delivered as the Hewitt Lectures of Columbia
University at Cooper Union in New York City during
the months of February and March, 1907. The purpose
of these lectures was to describe in concise outline the
Doctrine of Evolution, its basis in the facts of natural
history, and its wide and universal scope. They fall
naturally into two groups. Those of the first part deal
with matters of definition, with the essential character-
istics of living things, and, at greater length, with the
evidences of organic evolution. The lectures of the
second group take up the various aspects of human
evolution as a special instance of the general organic
process. In this latter part of the series, the subject
of physical evolution is first considered, and this is
followed by an analysis of human mental evolution;
the chapter on social evolution extends the funda-
mental principles to a field which is not usually con-
sidered by biologists, and its purpose is to demonstrate
the efficiency of the genetic method in this department
as in all others; finally, the principles are extended
to what is called ^^the higher human life," the realm,
namely, of ethical, religious, and theological ideas and
ideals.

Naturally, so broad a survey of knowledge could not
include any extensive array of specific details in any

vi PREFACE

one of its divisions; it was possible only to set forth
some of the more striking and significant facts which
would demonstrate the nature and meaning of that
department from which they were selected. The
illustrations were usually made concrete through the
use of photographs, which must naturally be lacking in
the present volume. In preparing the addresses for
publication, the verbal form of each evening's dis-
cussion has been somewhat changed, but there has been
no substantial alteration of the subjects actually dis-
cussed.

The choice of materials and the mode of their pre-
sentations were determined by the general purpose
of the whole course. The audiences were made up
almost exclusively of mature persons of cultivated
minds, but who were on the whole quite unfamiliar
with the technical facts of natural history. It was
necessary to disregard most of the problematical ele-
ments of the doctrine so as to bring out only the basic
and thoroughly substantiated principles of evolution.
The course was, in a word, a simple message to the un-
scientific ; and while it may seem at first that the dis-
cussions of the latter chapters lead to somewhat insecure
positions, it should be remembered that their purpose
was to bring forward the proof that even the so-called
higher elements of human life are subject to classifica-
tion and analysis, like the facts of the lower organic
world.

It may seem that the biologist is straying beyond his
subject when he undertakes to extend the principles of
organic evolution to those possessions of mankind that
seem to be unique. The task was undertaken in the

PREFACE VU

Hewitt Lectures because the writer holds the deeply
grounded conviction that evolution has been continuous
throughout, and that the study of lower organic forms
where laws reveal themselves in more fundamental
simpUcity must lead the investigator to employ and
apply those laws in the study of the highest natural
phenomena that can be found. Another motive was
equally strong. Too frequently men of science are
accused of restricting the appUcation of their results to
their own particular fields of inquiry. As individuals
they use their knowledge for the development of world
conceptions, which they are usually reluctant to dis-
play before the world. It is because I beheve that
the accusation is often only too well merited that I
have endeavored to show as well as circumstances
permit how universal is the scope of the doctrine based
upon the facts of biology, and how supreme are its
practical and dynamic values.

It remains only to state that the present volume
contains nothing new, either in fact or in principle;
the particular form and mode of presenting the evolu-
tionary history of nature may be considered as the
author's personal contribution to the subject. Nothing
has been stated that has not the sanction of high author-
ity as well as of the writer's own conviction; but it
will be clear that the believers in the truth of the analysis
as made in the later chapters may become progressively
fewer, as the various aspects of human life and of human
nature are severally treated. Nevertheless, I believe
that this volume presents a consistent reasonable view
that will not be essentially different from the con-
ceptions of all men of science who believe in evolution.

CONTENTS

CHAPTEB PAGB

I. Evolution. The Living Organism and its Natu-
ral History 1

II. The Structure and Development of Animals as

Evidence of Evolution .35

III. The Evidence of Fossil Remains .... 73

IV. Evolution as a Natural Process .... 106

V. The Physical Evolution of the Human Species

and of Human Races 150

VI. The Mental Evolution of Man .... 197

VII. Social Evolution as a Biological Process . . 241

VIII. Evolution and the Higher Human Life . . 278

be

EVOLUTION. THE LIVING ORGANISM AND ITS NATURAL

HISTORY

The Doctrine of Evolution is a body of principles
and facts concerning the present condition and past
history of the living and lifeless things that make up
the universe. It teaches that natural processes have
gone on in the earlier ages of the world as they do to-day,
and that natural forces have ordered the production
of all things about which we know.

It is difficult to find the right words with which to
begin the discussion of so vast a subject. As a general
statement the doctrine is perhaps the simplest formula
of natural science, although the facts and processes
which it summarizes are the most complex that the
human intellect can contemplate. Nothing in natural
history seems to be surer than evolution, and yet the
final solution of evolutionary problems defies the most
subtle skill of the trained analyst of nature's order.
No single human mind can contain all the facts of a
single small department of natural science, nor can one
mind comprehend fully the relations of all the various
departments of knowledge, but nevertheless evolution
seems to describe the history of all facts and their
relations throughout the entire field of knowledge.
Were it possible for a man to live a hundred years, he
could only begin the exploration of the vast domains

B 1

2 DOCTRINE OF EVOLUTION .

of science, and were his life prolonged indefinitely, his
task would remain forever unaccomplished, for prog-
ress in any direction would bring him inevitably to
newer and still unexplored regions of thought.

Therefore it would seem that we are attempting an
impossible task when we undertake in the brief time
before us the study of this universal principle and its
fundamental concepts and applications. But are the
difficulties insuperable? Truly our efforts would be
foredoomed to failure were it not that the materials
of knowledge are grouped in classes and departments
which may be illustrated by a few representative data.
And it is also true that every one has thought more or
less widely and deeply about human nature, about the
living world to which we belong, and about the cir-
cumstances that control our own lives and those of
our fellow creatures. Many times we withdraw from
the world of strenuous endeavor to think about the
*^ meaning of things," and upon the ' Vhy" and ''where-
fore" of existence itself. Every one possesses already
a fund of information that can be directly utiHzed
during the coming discussions ; for if evolution is true
as a universal principle, then it is as natural and every-
day a matter as nature and existence themselves, and
its materials must include the facts of daily life and
observation.

Although the doctrine of evolution was stated in
very nearly its present form more than a century ago,
much misunderstanding still exists as to its exact mean-
ing and nature and value ; and it is one of the primary
objects of these discussions to do away with certain
current errors of judgment about it. It is often sup-

THE LIVING ORGANISM 3

posed to be a remote and recondite subject, intelligible
only to the technical expert in knowledge, and apart
from the everyday world of life. It is more often
conceived as a metaphysical and philosophical system,
something antagonistic to the deep-rooted religious
instincts and the theological behefs of mankind. Truly
all the facts of knowledge are the materials of science,
but science is not met physics or philosophy or belief,
even though the student who employs scientific method
is inevitably brought to consider problems belonging to
these diverse fields of thought. A study of nervous
mechanism and organic structure leads to the philo-
sophical problem of the freedom of the will ; questions
as to the evolution of mind and the way mind and matter
are related force the investigator to consider the problem
of immortality. But these and similar subjects in the
field of extra-science are beyond its sphere for the very
good reason that scientific method, which we are to
define shortly, cannot be employed for their solution.
Evolution is a science; it is a description of nature's
order, and its materials are facts only. In method and
content it is the very science of sciences, describing
all and holding true throughout each one.

The overwhelming importance of knowing about
natural laws and universal principles is not often real-
ized. What have we to do with evolution and science ?
Are we not too busy with the ordering of our immediate
affairs to concern ourselves with such remote matters ?
So it may appear to many, who think that the study
of life and its origin, and of the vital facts about plants
and animals may be interesting and may possess a
certain intellectual value, but nothing more. The

4 DOCTRINE OF EVOLUTION

investigation of man and of men and of human life is
regarded by the majority as a mere cultural exercise
which has no further result than the recording of present
facts and past histories ; but it is far otherwise. Science
and evolution must deal with mere details about the
world at large, and with human ideals and with life
and conduct; and while their purpose is to describe
how nature works now and how it has progressed in
the past, their fullest value is realized in the sure guid-
ance they provide for our lives. This cannot be clear
until we reach the later portions of our subject, but
even at the outset we must recognize that knowledge
of the great rules of nature's game, in which we must
play our parts, is the most valuable intellectual posses-
sion we can obtain. If man and his place in nature,
his mind and social obligations, become intelligible, if
right and wrong, good and evil, and duty come to have
more definite and assignable values through an under-
standing of the results of science, then life may be fuller
and richer, better and more effective, in direct pro-
portion to this understanding of the harmony of the
universe.

And so we must approach the study of the several
divisions of our subject in this frame of mind. We
must meet many difficulties, of which the chief one is
perhaps our own human nature. For we as men are
involved, and it is hard indeed to take an impersonal
point of view, — to put aside all thoughts of the conse-
quences to us of evolution, if it is true. Yet emotion
and purely human interest are disturbing elements in
intellectual development which hamper the efforts of
reason to form assured conceptions. We must dis-

THE LIVING ORGANISM 5

regard for the time those insistent questions as to
higher human nature, even though we must inevitably
consider them at the last. Indeed, all the human
problems must be put aside until we have prepared the
way for their study by learning what evolution means,
what a living organism is, and how sure is the evidence
of organic transformation. When we know what
nature is like and what natural processes are, then we
may take up the questions of supreme and deep con-
cern about our own human lives.

Human curiosity has ever demanded answers to ques-
tions about the world and its make-up. The primi-
tive savage was concerned primarily with the everyday
work of seeking food and building huts and carrying on
warfare, and yet even he found time to classify the
objects of his world and to construct some theory about
the powers that made them. His attainments may
seem crude and childish to-day, but they were the
beginnings of classified knowledge, which advanced
or stood still as men found more or less time for obser-
vation and thought. Freed from the strife of primeval
and medieval life, more and more observers and thinkers
have enlarged the boundaries and developed the terri-
tory of the known. The history of human thought
itself demonstrates an evolution which began with the
savages' vague interpretation of the ^^what" and the
^^why" of the universe, and culminates in the science
of to-day.

What, now, is a science ? To many people the word
denotes something cold and unfeeUng and rigid, or

6 DOCTRINE OF EVOLUTION

something that is somehow apart from daily hfe and
antagonistic to freedom of thought. But this is far
from being true. Karl Pearson defines science as
organized knowledge^ and Huxley calls it organized
common sense. These definitions mean the same thing.
They mean that in order to know anything that de-
serves confidence, in order to obtain a real result, it
is necessary in the first place to establish the reality
of facts and to discriminate between the true, the not
so sure, the merely possible, and the false. Having
accurate and verified data, scientific method then
proceeds to classify them, and this is the organizing
of knowledge. The final process involves a summary
of the facts and their relations by some simple ex-
pression or formula. A good illustration of a scientific
principle is the natural law of gravitation. It states
simply that two bodies of matter attract one another
directly in proportion to their mass, and inversely in
proportion to the square of the distance between them.
In this concise rule are described the relations which
have been actually determined for masses of varying
sizes and at different distances apart, — for snowflakes
falling to the earth, for the avalanche on the mountain
slope, and for the planets of the solar system, moving
in celestial coordination.

Such a principle as the law of gravitation, like evolu-
tion, is true if the basic facts are true, if they are reason-
ably related, and if the conclusion is drawn reasonably
from them. It is true for all persons who possess
normal minds, and this is why Huxley speaks of science
as '^common sense," — that is, something which is a
reasonable and sensible part of the mental make-up of

THE LIVING ORGANISM 7

thinking persons that they can hold in common. The
form and method of science are fully set forth by these
definitions, and the purpose also is clearly revealed.
For the results of investigation are not merely formulae
which summarize experience as so much ^^ conceptual
shorthand/' as Karl Pearson puts it, but they must
serve also to describe what will probably be the orderly
workings of nature as future experience unfolds.
Human endeavor based upon a knowledge of scientific
principles must be far more reliable than where it is
guided by mere intuition or unreasoned belief, which may
or may not harmonize with the everyday world laws.
Just as the law of gravitation based upon past experience
provides the bridge builder and the architect with a
statement of conditions to be met, so we shall find that
the principles of evolution demonstrate the best means
of meeting the circumstances of life.

Evolution has developed, like all sciences, as the
method we have described has been employed. Al-
chemy became chemistry when the so-called facts of
the medievalist were scrutinized and the false were
discarded. Astrology was reorganized into astronomy
when real facts about the planets and stars were
separated from the belief that human lives were in-
fluenced by the heavenly bodies. Likewise the science
of life has undergone far-reaching changes in coming
down to its present form. All the principles of these
sciences are complete only in so far as they sum up in
the best way the whole range of facts that they describe.
They cannot be final until all that can be known is
known, — until the end of all knowledge and of time.
It is because he feels so sure of what has been gained

8 DOCTRINE OF EVOLUTION

that the man of science seems to the unscientific to
claim finahty for his results. He himself is the first to
point out that dogmatism is unjustified when its asser-
tions are not so thoroughly grounded in reasonable fact
as to render their contrary unthinkable. He seeks only
for truth, realizing that new discoveries must oblige
him to amend his statement of the laws of nature with
every decade. But the great bulk of knowledge con-
cerning life and living forms is so sure that science
asserts, with a decision often mistaken for dogmatism,
that evolution is a real natural process.

The conception of evolution in its turn now de-
mands a definite description. How are we to regard the
material things of the earth? Are they permanent
and unchanged since the beginning of time, un-
changing and unchangeable at the present? We do
not need Herbert Spencer's elaborate demonstration
that this is unthinkable, for we all know from daily
experience that things do change and that nothing is
immutable. Did things have a finite beginning, and
have they been '^made" by some supernatural force
or forces, personified or impersonal, different from those
agencies which we may see in operation at the present
time? So says the doctrine of special creation.
Finally, we may ask if things have changed as they
now change under the influence of what we call the
natural laws of the present, and which if they operated in
the past would bring the world and all that is therein
to be just what we find now. This is the teaching of
the doctrine of evolution. It is a simple brief state-

THE LIVING ORGANISM 9

ment of natural order. And because it has followed
the method of common sense, science asserts that
changes have taken place, that they are now taking
place, and furthermore that it is unnecessary to appeal
to other than everyday processes for an explanation
of the present order of things.

Wherever we look we see evidence of nature's change ;
every rain that falls washes the earth from the hills
and mountains into the valleys and into the streams
to be transported somewhere else; every wind that
blows produces its small or greater effect upon the face
of the earth ; the beating of the ocean's waves upon
the shore, the sweep of the great tides, — these, too,
have their transforming power. The geologists tell us
that such natural forces have remodeled and recast the
various areas of the earth and that they account for the
present structure of its surface. These men of science
and the astronomers and the physicists tell us that in
some early age the world was not a solid globe, with
continents and oceans on its surface, as now ; that it
was so very hot as to be semi-fluid or semi-solid in con-
sistency. They tell us that before this time it was still
more fluid, and even a mass of fiery vapors. The earth's
molten bulk was part of a mass which was still more vast,
and which included portions which have since condensed
to form the other bodies of the solar system, — Mars
and Jupiter and Venus and the rest, — while the sun
remains as the still fiery central core of the former
nebulous materials, which have undergone a natural
history of change to become the solar system. The
whole sweep of events included in this long history is
called cosmic evolution ; it is the greater and more inclu-

10 , DOCTRINE OF EVOLUTION

sive process comprising all the transformations which
can be observed now and which have occurred in the
past.

At a certain time in the earth's history, after the hard
outer crust had been formed, it became possible for
living materials to arise and for simple primitive
creatures to exist. Thus began the process of organic
evolution — the natural history of living things — with
which we are concerned in this and later addresses.
Organic evolution is thus a part of the greater cosmic
process. As such it does not deal with the origin of
life, but it begins with life, and concerns itself with the
evolution of living things. And while the investigator
is inevitably brought to consider the fundamental
question as to the way the first life began, as a student
of organic forms he takes hfe for granted and studies
only the relationships and characteristics of animals
and plants, and their origins.

But even as a preliminary definition, the statement
that organic evolution means natural change does
not satisfy us. We need a fuller statement of what it
is and what it involves, and I think that it would be
best to begin, not with the human being in which we
are so directly interested, nor even with one of the
lower creatures, but with something, as an analogy,
which will make it possible for us to understand im-
mediately what is meant by the evolution of a man,
or of a horse, or of an oak tree. The first steam loco-
motive that we know about, like that of Stephenson, was
a crude mechanism with a primitive boiler and steam-
chest and drive- wheels, and as a whole it had but a low
degree of efficiency measured by our modern standard ;

THE LIVING ORGANISM 11

but as time went on inventive genius changed one little
part after another until greater and greater efficiency
was obtained, and at the present time we find many
varied products of locomotive evolution. The great
freight locomotive of the transcontinental lines, the
swift engine of the express trains, the little coughing
switch engine of the railroad yards, and the now extinct
type that used to run so recently on the elevated rail-
roads, are all in a true sense the descendants of a common
ancestor, namely the locomotive of Stephenson. Each
one has evolved by transformations of its various parts,
and in its evolution it has become adapted or fitted to
peculiar circumstances. We do not expect the freight
locomotive with its eight or ten powerful drive-wheels to
carry the light loads of suburban traffic, nor do we expect
to see a little switch engine attempt to draw '' the Twen-
tieth Century Limited" to Chicago. In the evolution,
then, of modern locomotives, differences have come
about, even though the common ancestor is one single
type ; and these differences have an adaptive value to
certain specific conditions. A second illustration will
be useful. Fulton's steamboat of just a century ago
was in a certain true sense the ancestor of the ^'Lusi-
tania, " with its deep keel and screw propellers, of the
side-wheel steamship for river and harbor traffic like
the ^'Priscilla," of the stern-wheel flat-bottom boats of
the Mississippi, and of the battleship, and the tug boat.
As in the first instance, we know that each modern type
has developed through the accumulation of changes,
which changes are likewise adjustments to different
conditions. The diversity of modern types of steam-
ships may be attributed therefore to adaptation.

12 DOCTRINE OF EVOLUTION

The several kinds are no more interchangeable than are
the different forms of locomotives that we have men-
tioned. The flat-bottom boat of the Mississippi would
not venture to cross the Atlantic Ocean in winter, nor
would the ^'Lusitania" attempt to plow a way up
the shallow mud-banked Mississippi. These products
of mechanical development are not efficient unless they
run under the circumstances which have controlled
their construction, unless they are fitted or adapted to
the conditions under which they must operate.

Evolution, then, means descent with adaptive modifica-
tion. We must examine the various kinds of living
creatures everywhere to see if they, like the machines,
exhibit in their make-up similar elements which indicate
their common ancestry in an earlier age, and if we can
interpret their differences as the results of modifica-
tions which fit them to occupy different place in nature.

Two objections to the employment of these analogies
will present themselves at once. The definition may be
all very well as far as the machines are concerned, but,
it may be asked, should a living thing like a horse or a
dog be compared with the steamship or the locomotive ?
Can we look upon the living thing as a mechanism in
the proper sense of the word ? A second objection will
be that human invention and ingenuity have controlled
the evolution of the steamship and engine by the per-
fection of newer and more efficient parts. It is certainly
true that organic evolution cannot be controlled in the
same way by men, and that science has not yet found
out what all the factors are. And yet we are going to
learn in a later discussion that nature's method of trans-
forming organisms in the course of evolution is strikingly

THE LIVING ORGANISM 13

J^ similar to the human process of trial and error which
has brought the diverse modern mechanisms to their
present conditions of efficiency. This matter, however,
must remain for the time just as it stands. The first
objection, namely, that an organism ought not to be
viewed as a machine, is one that we must meet immedi-
ately, because it is necessary at the very outset to gain
a clear idea of the essentially mechanical nature of
living things and of their relations to the conditions
under which they live. It is only when we have such
a clear understanding that we can profitably pursue
the further inquiries into the evidence of evolution.
Our first real task, therefore, is an inquiry into certain
fundamental questions about life and living things, upon
which we shall build as we proceed.

All living things possess three general properties which
seem to be unique ; these are a peculiar chemical con-
stitution, the power of repairing themselves as their
tissues wear out, and the abihty to grow and multiply.
The third property is so familiar that we fail to see how
sharply it distinguishes the creatures of the organic
world. To realize this we have only to imagine how
strange it would seem if locomotives and steamships
detached small portions of themselves which could
grow into the full forms of the parent mechanisms.
Equally distinctive is the marvelous natural power
which enables an animal to re-build its tissues as they
are continually used up in the processes of living ; for no
man-made, self-sustaining mechanism has ever been
perfected. The property of chemical composition is be-

14 DOCTRINE OF EVOLUTION

lieved by science to be the basis of the second and the
third ; but this matter of chemical constitution must take
its proper place in the series of structural characters,
which we shall discuss further on as we develop the
conception of organic mechanism.

Whatever definition we may employ for a machine
or an engine, we cannot exclude the living organism
from its scope. As a ^^ device for transforming and
utilizing energy" the living organism differs not at all
from any ''dead" machine, however complex or simple.
The greatest lesson of physiological science is that the
operations of the different parts of the living thing, as
well as of the whole organism itself, are mechanical;
that is, they are the same under similar circumstances.
The living creature secures fresh supplies of matter and
energy from the environment outside of itself ; these
provide the fuel and power for the performance of the
various tasks demanded of an efficient living thing,
and they are the sources upon which the organism
draws when it rebuilds its wasted tissues and replenishes
its energies. The vital tasks of all organisms must be
considered in due course, but at first it is necessary to
justify our analogies by analyzing the structural char-
acteristics of animals and plants, just as we might
study locomotives in a mechanical museum before we
should see how they work upon the rails.

Among the familiar facts which science reveals in a|
new light are the peculiarly definite qualities of living
things as regards size and form. There is no general \
agreement in these matters among the things of the
inorganic world. Water is water, whether it is a drop
or the Pacific Ocean; stone is stone, whether it is a

THE LIVING ORGANISM 15

pebble, a granite block, or a solid peak of the Rocky
Mountains. It is true that there is a considerable range
in size between the microscopic bacterium at one ex-
treme and the elephant or whale at the other, but this
is far less extensive than in the case of lifeless things
like water and stone. In physical respects, water may
be a fluid, or a gas in the form of steam, or a solid, as a
crystal of snow or a block of ice. But the essential
materials of hving things agree throughout the entire
range of plant and animal forms in having a jelly like
consistency.

But by far the most striking and important character-
istic of living things is their definite and restricted
chemical composition. Out of the eighty and more
chemical elements known to science, the essential
substance of living creatures is formed by only six to
twelve. These are the simple and obvious character-
istics of living things which are denoted by the word
'^organic.'' Everyone has a general idea of what this
expression signifies, but it is important to realize that
it means, in exact scientific terms, — constituted in
definite and peculiar ways.

The living thing, then, possesses a definite constitu-
tion, which is a mechanical characteristic, while further-
more it is related to its surroundings in a hard and
fast way. Just as locomotives are different in structure
so that they may operate successfully under different
conditions, so the definite characteristics of living things
are exactly what they should be in order that organ-
isms may be adjusted or fitted into the places in nature
which they occupy. This universal relation to the en-
vironment is called adaptation. It is only too obvious

16 DOCTRINE OF EVOLUTION

when our attention is directed to it, but it is something
which may have escaped our notice because it is so
natural and universal. The trunk of a tree bears the
limbs and branches and leaves above the ground, while
the roots run out into the surrounding soil from the
foot of the trunk; they do not grow up into the air.
An animal walks upon its legs, the wings of a bird are
just where they should be in order that they may be use-
ful as organs of flight. And these mechanical adjust-
ments in the case of living creatures occur for the same
reason as in mechanisms like the steamship, which has
the propeller at its hinder end and not elsewhere, and
which bears its masts erect instead of in any other way.
The next step in the analysis of organisms reveals the
same wonderful* though familiar characteristics. The
living organism is composed of parts which are called /
organs, and these differ from one another in structural I
and functional respects. Each of them performs a
special task which the others do not, and each differen-
tiated organ does its part to make the whole creature an
efficient mechanism. The leg of the frog is an organ
of locomotion, the heart is a device for pumping blood,
the stomach accomplishes digestion, while the brain and
nerves keep the parts working in harmony and also
provide for the proper relation of the whole creature to
its environment. So rigidly are these organs special-
ized in structure and in function that they cannot re-
place one another, any more than the drive wheels of
the locomotive could replace the smokestack, or the
boiler be interchanged with either of these. All of the
organs are thus fitted or adjusted to a particular place
in the body where they may most efficiently perform

THE LIVING ORGANISM 17

their duties. Each organ therefore occupies a particular
place in an organic environment, so to speak. Thus the
principle of adaptation holds true for the organs which
constitute an organism, as well as for organisms them-
selves in their relations to their surroundings.

The various organs of living things are grouped so

I as to form the several organic systems. There are

•^' eight of these, and each performs a group of related tasks
I which are necessary for complete life. The alimentary

""1 system concerns itself with three things : it gets food
into the body, or ingests ; it transforms the insoluble
foods by the intricate chemical processes of digestion;
and it absorbs or takes into itself the transformed food
substances, which are then passed on to the other parts
of the body. It is hardly necessary to point out that
the ingestive stru'ctures for taking food and preparing
it mechanically lie at and near the mouth, while the
digesting parts, hke the stomach, come next, because
chemical transformation is the next thing to be done ;
while finally the absorbing portions of the tract, or. the
intestines, come last. The second group of organs, like
gills and lungs, supplies the oxygen, which is as

.f necessary for life as food itself ; this respiratory system
also provides for the passage from the body of certain
of the waste gases, like carbonic acid gas and water
vapor. The excretory system of kidneys and similar
structures collects the ash-waste produced by the burn-
ing tissues, and discharges this from the whole mechan-

c. ism, like the ash hoist of a steamship. The circulatory
system, made up of smaller and larger vessels, with or
without a heart, transports and propels the blood
through the body, carrying the absorbed foods, the sup-

18 DOCTRINE OF EVOLUTION

plies of oxygen, and the waste substances of various
kinds. All of these four systems are concerned with
" commissary " problems, so to speak, which every in-
dividual must solve for and by itself.

Another group of systems is concerned with wider rela-
tions of the individual and its activities. For example,
the motor system accomplishes the movements of the
various organs within the body, and it also enables the or-
ganism to move about ; thus it provides for motion and
locomotion. Systems of support, comprising bones or
shells, occur in many animals where the other organs are
soft or weak. Perhaps the most interesting of the in-
dividual systems of relation is the nervous system.
The strands of its nerve fibers and its groups of cells
keep the various organs of the body properly coor-
dinated, whereas in the second place, through the
sensitive structures at the surface of the body, they
receive the impressions from the outside world and so
enable the organism to relate itself properly to its en-
vironment. The last organic system differs from the
other seven in that the performance of its task is of
far less importance to the individual than it is to the
race as a whole. It is the reproductive system, with
a function that must be always biologically supreme.
We can very readily see why this must be so ; it is be-
cause nature has no place for a species which permits
the performance of any individual function to gain
ascendency over the necessary task of perpetuating the
kind. Nature does not tolerate race suicide.

All organisms must perform these eight functions
in one way or another. The bacterium, the simplest
animal, the lowest plant, the higher plants and animals,

THE LIVING ORGANISM 19

— all of these have a biological problem to solve which
comprises eight terms or parts, no more and no less.
This is surely an astonishing agreement when we con-
sider the varied forms of living creatm*es. And perhaps
when we see that this is true we may understand why
adaptation is a characteristic of all organisms, for they
all have similar biological problems to solve, and their
lives must necessarily be adjusted in somewhat similar
ways to their surroundings.

Carrying the analysis of organic structure one step
further, it is found that the various organisms are them-
selves complex, being composed of tissues, A frog's leg
as an organ of locomotion is composed of the protecting
skin on the outside, the muscles, blood vessels, and nerves
below, and in the center the bony supports of the whole
limb. Like the organs, these tissues are differentiated
structurally and functionally, ' and they also are so
placed and related as to exhibit the kind of mechanical
adjustment which we call adaptation. The tissues,
then, in their relations to the organs are like the organs
in their relations to the whole creature, i.e. adapted
to specific situations where they may most satisfactorily
perform their tasks.

Finally, in the last analysis, all organisms and organs
and tissues can be resolved into elements which are
called cells. They are not little hollow cases, it is true,
although for historical reasons we employ a word that
implies such a condition. They are unitary masses of
living matter with a peculiar central body or nucleus,
and every tissue of every living thing is composed of
them.

The cells of bone differ from those of cartilage mainly

20 DOCTRINE OF EVOLUTION

in the different consistency of the substances secreted
by the cells to lie between them; skin cells are soft-
walled masses lying close together; even blood is a
tissue^ although it is fluid and its cells are the corpuscles
which float freely in a hquid serum. Thus an organism
proves to be a complex mechanism composed of cells
as structural units, just as a building is ultimately a
collection of bricks and girders and bolts, related to
one another in definite ways.

Our analysis reveals the living creature in an entirely
new light, not only as a machinelike structure whose
parts are marvelously formed and coordinated in
material respects, but also as one whose activities
or workings are ultimately cellular in origin. Struc-
ture and function are inseparable, and if an animal
or a plant is an aggregate of cells, then its whole varied
life must be the sum total of the lives of its constituent
cells. Should these units be subtracted from an ani-
mal, one by one, there would be no material organism
left when the last cells had been disassociated, and there
would be no organic activity remaining when the last
individual cell-life was destroyed. All the various
things we do in the performance of our daily tasks are
done by the combined action of our muscle and nerve
and other tissue cells ; our life is all of their lives, and
nothing more. The cell, then, is the physiological or
functional unit, as truly as it is the material element of
the organic world. Being combined with countless
others, specialized in various ways, relations are estab-
lished which are like those exhibited by the human be-
ings constituting a nation. In this case the life of the
community consists of the activities of the diverse

THE LIVING ORGANISM 21

human units that make it up. The farmer, the manu-
facturer, the soldier, clerk, and artisan do not all work
in the same way; they undertake one or another of
the economic tasks which they may be best fitted by
circumstances to perform. Their differentiation and
division of labor are identical with the diversity in
structure and in function as well, exhibited by the cells
of a living creature. We might speak of the several
states as so many organs of our own nation ; the com-
mercial or farming or manufacturing communities of
a state would be hke the tissues forming an organ,
made up ultimately of human units, which, like cells,
are engaged in similar activities. As the individual
human hves and the activities of differentiated eco-
nomic groups constitute the life of a nation and
national existence, so cell-lives make the living of an
organism, and the expressions ^^ division of labor" and
^^ differentiation'^ come to have a biological meaning
and application.

The cell, then, is in all respects the very unit of the
organic world. Not only is it the ultimate structural
element of all the more familiar animals and plants
that we know, as the foregoing analysis demonstrates,
but, in the second place, the microscope reveals simple
little organisms, like Amoeba, the yeast plant and bacteria,
which consist throughout their lives of just one cell
and nothing more. Still more wonderful is the fact that
the larger complex organisms actually begin existence
as single cells. In three ways, therefore, — the ana-
lytic, the comparative, and the developmental, — the

22 DOCTRINE OF EVOLUTION

cell proves to be the '^organic individual of the first
order." As the ultimate biological unit, its essential
nature must possess a profound interest, for in its
substance resides the secret of life.

This wonderful physical basis of life is called proto-
plasm. It contains three kinds of chemical compounds
known as the proteins, carbohydrates, and hydro-
carbons. Proteins are invariably present in living cells,
and are made up of carbon, hydrogen, nitrogen, sulphur,
and usually a little phosphorus. The elements are
also combined in a very complex chemical way. For
example, the substance called haemoglobin is the protein
which exists in the red blood cells and which causes those
cells to appear light red or yellow when seen singly.
Its chemical formula states the precise number of atoms
which enter into the constitution of a single molecule
as : CgQoHggQNig^FeOi^g. This is truly a marvelously
complex substance when compared with the materials
of the inorganic world, like water, for example, which has
the formula HgO. And just as the peculiar properties
of HgO are given to it by the properties of the hydrogen
and the oxygen which combine to form it, just so, the
scientist believes, the marvelous properties of protein
are due to the assemblage of the properties of the
carbon and hydrogen and other elements which enter
into its composition.

It would be interesting to see how each one of these
elements contributes some particular characteristic
to the whole compound. The carbon atom, for ex-
ample, is prone to combine with other atoms in defi-
nite varied ways, and the high degree of complexity
which the protein molecule possesses may depend in

V

THE LIVING ORGANISM 23

greater part upon the combining power of its carbon
elements. The nitrogen atom makes the protein an
extremely volatile compound, so that the latter burns
readily in the"tissue cells ; and the hydrogen and oxygen
bring their specific characteristics to the total molecule.
And furthermore, it is evident that the great complexity
of this constituent, protein, gives to protoplasm its
power of doing work, or, in a word, its power of living.
In constructing it, much energy has been absorbed and
stored up as potential energy, and so, like the stored-up
energy in a watch spring or in gunpowder, this may be
converted, under proper conditions, into the kinetic
energy and the work of actual operation. On account
of its peculiar and complex nature, it possesses great
capacity for burning or oxidization, thus serving as a
source of vital power. It burns in the living tissue just
as coal oxidizes in the boiler of an engine ; its atoms fly
apart and unite with oxygen so as to satisfy their chem-
ical affinities for this substance. If we could only see
what happens to the protein molecule when it under-
goes oxidization, we would witness a violent explosion,
like that of a mass of gunpowder. And the astonishing
fact is that this process is actually the same for the living
molecule, for exploding gunpowder, and for the fuel
which burns in the locomotive boiler. Does this mean
that the essential process of what we call life is a chemi-
cal one? So it would seem on the basis of this fact
alone, but a conclusion must be deferred until we reach
a later point.

The second kind of substance which we find in pro-
toplasm is the carbohydrate. A typical member of
this group is common sugar, CqH^^Oq ; another sugar has

24 DOCTRINE OF EVOLUTION

the formula 012^22^11- Starch is again a typical carbo-
hydrate, and its formula is CgHj^Og, or some multiple of
this. One sees at a glance that these substances agree
in having twice as many hydrogen atoms as there are
oxygen atoms, the same proportion that the hydrogen
bears to the oxygen in the compound water, — a
characteristic which makes it easy to remember the
general constitution of carbohydrate as compared
with the protein. The substances of this second class
are obviously much less complex, both as regards the
different kinds of atoms and in respect to the numbers
of each kind that enter into the formation of a single
molecule. Therefore the carbohydrates do not possess
so much power or energy as the protein molecule ;
in short, they are not such good fuels for the living
mechanism.

Finally, we find almost always in protoplasm other
substances composed of carbon and hydrogen and oxygen
which are called hydrocarbons, distinguished from carbo-
hydrates by the fact that the number of oxygen atoms is
less than half the number of hydrogen atoms. These
substances are the fats and oils of various kinds, less
powerful sources of energy than the proteins, but they
contain more potential energy than the carbohydrates
because they are more oxidizable.

Besides the characteristic substances of these three
classes, protoplasm contains certain other chemical
compounds, like the various salts of sodium, chlorine,
magnesium and potassium, and a few others, which
bring the list of chemical elements to the number twelve.
We have already noted how strikingly small and
restricted is the hst of elements composing living

THE LIVING ORGANISM 25

matter as compared with the long array of eighty-odd
different kinds of chemical atoms existing in the world
as a whole.

But an astonishing result is reached through the brief
analysis we have just made. It is this : we do not
find peculiar kinds of atoms which occur exclusively
in living matter ; the materials are exactly the same
as those of the outer world. In short, the elements
of both the organic and inorganic divisions of the
universe prove to be the same. Carbon is carbon,
whether it is part of the substance of a living brain cell,
or black inert coal, or the glistening diamond, or an
incandescent part of the fiery sun. Hydrogen is the
same, whether it be a constituent of the ocean, of the air,
or of the living muscle fiber. And so it is with all of
the other elements of the living mechanism. This starts
us upon a line of thought which leads to a significant
conclusion, namely, that a living thing which seems so
distinct and permanent is after all only a temporary ag-
gregate of elements which come to it from the not-living
world; existing for a time in peculiar combinations
which render life possible, they pass incessantly away
from the Hving thing and return to the inorganic world.
Every breath we draw sends out particles which were
at one time living portions of ourselves ; every move-
ment we make involves the destruction of living muscle
cells, whose protoplasm breaks down into the ash and
gas and fluid wastes which eventually return to the
world of dead things. A tree loses its living leaves with
each recurring season, and the antlers of the stag are
lost annually, to be replaced anew. Indeed the major
part of some organisms is itself actually dead. The

I

26 DOCTRINE OF EVOLUTION

bones and hair and nails of such an animal as a cat are
almost entirely lifeless, even though they are integral
and necessary portions of the organism as a whole.
They are constructed by Hving protoplasm which has
died in their making. Thus without going beyond the
boundaries of the individual body, these substances have
passed from the sphere of life, and are dead. The ap-
parent gap on the other side between the lifeless and
living world is equally imaginary, for our living sub-
stance is continually replenished and rebuilt from the
elements of our dead foods. So, as Huxley says, a
living organism is like a flame or a whirlpool, which is
an ever changing though seemingly constant individual-
ity. We look at a gas flame, and we see in the flame
itself those particles of gas which have come through
the pipe to be agitated violently in the higher temper-
ature of the flame as they are oxidized or burnt. These
particles immediately pass off as carbonic acid gas and
water vapor which are no longer parts of the flame.
A fountain is continually replenished by the water
which is not-fountain, but which becomes for the time
a part of the graceful jet, falling out and away as it
leaves the fountain itself. Just so a living organism
is an ever changing, ever renewed, and ever destroyed
mass of little particles — the atoms of the inorganic
world which combine and come to life for a time, but
which return inevitably to the world of lifeless things.
This is one of the most fundamental facts of biology.
The independence of a living thing like a human being
or a crustacean is a product of the imagination. How
can we be independent of the environment when we
are interlocked in so many ways with inorganic nature ?

THE LIVING ORGANISM 27

Our very substance with its energies has been wrested
from the environment ; and as we, like all other living
things, must replenish our tissues as we wear out in the
very act of living, we cannot cease to maintain the
closest possible relations with the environment with-
out surrendering our existence in the battle of life.

From the foregoing discussion, it will be evident, I
am sure, that there is ample justification for the biologi-
cal dictum that a living individual is a mechanism.
Not only is the organism composed always of cell
units grouped mechanically in tissues and organs and
organic systems ; not only are the operations which
make up its hfe constant and regular under similar
conditions ; not only is the whole creature mechanically
connected with the inorganic world ; but above all the
whole activity of a biological individual is concerned
necessarily and again mechanically with the acquisition
of materials endowed with energy, which materials and
energy are mechanically transformed into Hving matter
and its life. Even though an organism is so much
more complex than a locomotive, and so plastic, never-
theless, in so far as both are mechanisms, the conception
of the evolution of the former may be much more readily
understood through a knowledge of the historical trans-
formation of the latter.

What, now, is life? To most people '4ife seems to
be something which enters into a combination of carbon
and hydrogen and the other elements, and makes this
complex substance, the protoplasm, perform its va-
rious activities." Nearly every one finds it difiScult

28 DOCTRINE OF EVOLUTION

to regard life and vitality as anything but actuating
principles that exist apart from the materials into
which they enter, and which they seem to make alive.
According to this general conception, "Me is something
like an engineer who climbs into the cab of the locomo-
tive and pulls the levers which make it go," as health
might supposedly be regarded as something that does
not inhere in well-being, but gets into the body to alter
it. But is this conception really justified by the facts
of animal structure and physiology? Let us recall
the steps of our analysis. The living organism is a
collection of differentiated parts, the organs; the
life of an organism is a series of activities of the several
organic systems and organs. If we could take away
one organ after another, there would be nothing left
after the last part had been subtracted. In a similar
manner, the activities of organs prove to be the com-
bined activities of the tissue-cells, and again the truth
of this statement will be clear when we imagine the
result of taking away one cell after another from
organisms like the frog or tree. When the last cell
had been withdrawn, there would be nothing left of
the frog's structure, and there would be no element
of the frog's life. It is true that the particular way the
tissue-cells are combined is of primary importance, but
it is none the less true that the life of a cell is the kind
of element out of which the life of even the most com-
plex organism is built. And we have seen that the
essential substance of a cell is a complex chemical
compound we call protoplasm, whose elements are
identical with chemical substances outside the living
world. Is there any ground for supposing that the

THE LIVING ORGANISM 29

properties of protoplasm are due to any other causes
than those which may be found in the chemical and
physical constitution of protoplasm? In brief, is life
physics and chemistry? Nowadays the majority of
biologists believe that it is. Just as the properties
of water are contributed by the elements hydrogen and
oxygto which unite to form it, just so the marvelous
properties of protoplasm are regarded as the inevitable
derivatives of the combined properties of the various
chemical elements which constitute protoplasm. Biolo-
gists have known for more than a century, since the
work of Lavoisier and Laplace in 1780, that the funda-
mental process of the living mechanism is oxidation,
and that this process is the same, as they said, for the
burning candle and the guinea pig. Beginning with
Woehler, in 1828, scores of students of physiological
chemistry have duplicated the chemical processes of
living matter, which were regarded as so peculiar to the
living organism that they seemed to be due to the oper-
ation of a non-mechanical and vital cause. The inves-
tigator mentioned was the first to construct artificially
from inorganic substances the nitrogen-containing
ash product of the living organism called urea. Now
hundreds of so-called organic compounds have been
made synthetically and their number is added to week
after week. Therefore, the biologist who finds that a
phj^sical and chemical analysis of some vital processes
is possible, and that the analysis is being extended
with astonishing rapidity, finds himself unable to
regard protoplasmic activity as anything different in
kind or category from the processes of physics and
chemistry which go on in the world of dead things.

30 DOCTRINE OF EVOLUTION

It is true that even at the present time some biologists
are reluctant to accept the thoroughgoing mechanical
interpretation of organic phenomena, partly because
these are so complex that their ultimate constituents
cannot be discerned, but more often on account of the
apparently purposeful nature of biological processes.
Some, indeed, have gone so far as to postulate some-
thing like consciousness which controls and directs the
formation of protoplasm, and the exercise of its dis-
tinctive properties in the way of growth, reproduction,
and embryonic development into the adapted adult.
But the fact remains that wherever analysis has been
possible the constituent elements of an organic process
prove to be physical and chemical. Protoplasm differs
from inorganic materials only in its complexity and
in the properties which seem to owe their existence
to this complexity. As Huxley points out, it is no more
justifiable to postulate the existence of a vitalistic
principle in protoplasm than it would be to set up an
aquosity" to account for the properties of water, or a
saltness" for the qualities of a certain combina-
tion of sodium and chlorine. We may not know how
the elements produce the properties of the compound,
but we do know that such properties are the invariable
products of their respective constituents in combina-
tion. As far as the evidence goes, it tells strongly and
invariably in favor of the mechanistic interpretation.

Under the present limitations, it is impossible to give
this subject the further discussion it deserves. It is
not our purpose to review the origin of life in times
past, and the origin of living matter from inorganic
constituents, though the subject is one of the most

ii

THE LIVING ORGANISM 31

important in the field of cosmic evolution. We must
begin with the living organism ; and how the first one
arose must be of less importance to us than the knowl-
edge of its mechanical constitution and of its mechani-
cal operation. Of far greater value is the realization
that a living creature is not an independent thing, but
that, on the contrary, it must hold the closest possible
relations with the world of materials and energies con-
stituting its environment. We must again insist upon
the importance of that mechanical adjustment to the
conditions of life which is the universal characteristic
of plants and animals. It is the history of these crea-
tures and the origin of their adapted conditions that
we are called upon to study. We must scrutinize the
nature of to-day to see if we can find evidence that
evolution is true, and if we can discern the forces which,
acting upon the living mechanism as man has dealt
with machines, might bring the various species of the
present day to their modern forms.

We have now learned that evolution means a common
ancestry of living forms that have come to differ in the
course of time ; our common reason has shown us also
that organisms are in a true sense complicated chemical
mechanisms adapted to meet the conditions under which
they must operate. We come now to the evidences
offered by the organic world that evolution is true and
that natural forces control its workings. Clearly the
examination of the matter of fact is independent of the
question of method. For just as the chemist may ex-
periment with various substances to see if they will

32 DOCTRINE OF EVOLUTION

dissolve in water and not in alcohol before it is neces-
sary or desirable for him to take up the further studies
of the laws of solution, so reasonable grounds must be
found for regarding evolution as true before passing to
its method of accomplishment. And in the following
discussions, the animals will be used almost exclusively,
not because the study of plants fails to discover the
same relations and principles, but because the better
known animal series is more varied and extensive,
and above all for the reason that the human organism
arrays itself as the highest term of the animal series.

In the complete scheme adopted by most naturalists,
five categories include the evidences bearing upon the
fact of evolution. These are Classification; Comparative
Anatomy, or Morphology ; Comparative Development,
or Embryology ; Palceontology, which comprises the facts
provided by fossil relics of animals and plants of earlier
geological ages ; and Geographical Distribution. Each of
these divisions includes a descriptive and analytical
series of facts, whose characteristics are '^explained" or
summarized in the form of the general principles of
the respective divisions. Such principles, taken singly
and collectively, constitute the evidences of evolution.

The particular nature of any one of these categories,
evolved in the development of science practically in the
order stated, depends upon the special quality of an
animal which it selects for comparison and organization
in connection with other similar facts, and also in its
own mode of viewing its facts. One and the same or-
ganism may present materials for two, three, or even
all five of these divisions, for they are by no means
mutually exclusive. For example, a common cat pos-

THE LIVING ORGANISM 33

sesses certain definite characteristics which give it a
particular place when animals more or less like it are
grouped or classified according to their degrees of re-
semblance and difference, in small genera of very similar
forms, in larger tribes or orders of similar genera, and in
more and more inclusive groups of these lesser divisions,
such as the classes and phyla, or main branches of the
animal tree. The conamon cat and its relatives are
even earlier to be regarded as anatomical subjects, and
their thorough analysis belongs to comparative anat-
omy, — a name which explains itself. The purpose
of this department of natural history is to explore the
entire range of animal forms and animal structures, and
to determine the degree of resemblance and difference
exhibited by the general characters of entire organisms
and by the special qualities of their several systems
of organs. It provides the data from which classifica-
tion selects those which indicate mutual affinities with
greatest precision and surety. But its materials are
all the facts of animal structure, and because each and
every known organism can be and must be studied,
the investigator engaged in formulating the evidence
of evolution has at his disposal all the data referring to
the entire realm of animals. The data of embryology
are likewise coextensive with the territory of the animal
world, for we do not know of any form which does not
change in the course of its life history. An adult cat
is the product of a kitten which is itself the result of a
long series of changes from earlier and simpler conditions.
In so far as it deals with structures in the making, em-
bryology is a study of anatomy, but as it is concerned
primarily with all of the plastic remodeling which an-

34 DOCTRINE OF EVOLUTION

imals undergo during the production of their final forms,
it is an independent study. Nevertheless we shall learn
how intimate are the relations of these two divisions of
zoology and how the evolutionary teachings of each body
of fact support and supplement those of the other.

Palaeontology searches everywhere among the de-
posits of earlier ages for links to be fitted into their
proper sequence of time, from which it constructs the
chain of diverse types leading down to the species of
the present. A cat of to-day is therefore viewed in
an entirely different connection, as the last term in a
consecutive series of species. Forming alliances w^ith
geology, and even with physics and chemistry, this
department of zoology endeavors to reconstruct the
past from what it learns to-day about organisms and
the conditions under which they live. Finally the
observations that cats of various kinds do not occur
everywhere in the world, but only in certain more or
less restricted localities, belong to the subject of geo-
graphical distribution, and illustrate its nature.

Our task is to learn the teachings of these several
divisions by recalling and putting together what we
know already about the commonest animals, or noting
what can be observed in a visit to a zoological garden
and aquariimi. On account of the present limitations
of time, the subject of classification will be combined
with comparative anatomy ; embryology will be taken
up together with these subjects ; palaeontology will be
the main subject of the next discussion, which will in-
clude also a brief statement of the meaning of dis-
tribution. Then we will be prepared to study nature
to see how evolution works.

II

THE STRUCTURE AND DEVELOPMENT OF ANIMALS AS

EVIDENCE OF EVOLUTION

In order to become acquainted with the way the
structures of animals provide evidences of evolution, it
is by no means necessary to review the entire range of
their forms, because research has discovered that the
principles of relationship are universal among animals,
and that any group of examples will demonstrate what
is taught by comparative anatomy as a whole. The
commonest creatures may serve us best in order that
we may come to view evolution as a process that in-
volves each and every living thing that we know, and
not as something which belongs only to the remote and
unknown past.

Let us begin with the common cat and the group of
carnivora or flesh-eating animals to which it belongs.
As we pass along the streets of the city, we will see many
cats which differ in some details, though they resemble
one another closely. While they vary somewhat in
form, the range in this quality is not so noticeable as in
the matter of color; some of them will be gray, some
maltese, while others will be yellowish or black, and
they will differ in the striped or spotted character of
their coloration. We readily classify them all as ^' cats "
in spite of their differences, because they are alike in

35

36 DOCTRINE OF EVOLUTION

so many ways that we have learned to associate as the
distinguishing characteristics of these animals, and to
label — ^'cat.'' The animals which we might see in a
walk of several blocks may reasonably be regarded as
offspring of the same pair of ancestors of a few years
back, even though they are dissimilar. We all know that
the kittens of one and the same litter vary : no two of
them are ever exactly alike in color or disposition or
voice or size, nor is any one identical with either of its
parents, although it may be necessary to employ exact
means of measuring them in order to demonstrate their
variation. The fact of difference, then, is surely not
inconsistent with even the closest ties of blood, and we
do not need to go beyond the scope of daily observation
to find that this is true in nature wherever we look.

Should we extend our observations so as to include
the cats of Boston and Philadelphia and San Francisco,
the animals would probably vary over a wider range,
but they would be so similar to New York cats in their
make-up that we would have no difficulty in regarding
them and all the others of the United States as the
descendants of a single pair of ancestors, perhaps
brought over in the '^Mayflower." But why does this
view seem justified? Because experience has taught
us that the living things which resemble each other
most closely are those which are most intimately bound
by ties of blood and common heritage. It is ^'natural"
for relatives to resemble one another more than per-
sons not related, and for brothers and sisters to be more
alike than cousins. Science does not refer to something
outside everyday observation when it states that the
possession by two animals of a great body of similar

STRUCTURE AND DEVELOPMENT 37

characters beneath their minor differences is an indication
of their common ancestry.

Thus at the very outset our simple illustration es-
tablishes the most fundamental principle of comparative
anatomy. Let us see how it works further. The
Manx cat possesses an abbreviated tail, although in
other respects it is practically the same as the familiar
long-tailed form; the Angora and the Persian differ
in having long hair. All of these animals are so much
alike in so many respects, and so closely resemble
the wild cats, that it is not unreasonable to regard them
all as the descendants of the same original wild ances-
tors, and as the varying products of lines which branched
out from the same stock in different directions and
at different times. It is, in a word, their ^^cat-ness'^
which demonstrates their relationships. But common
sense need not stop here. Guided by the facts of ana-
tomical similarity, it convinces us that the dun-colored
lion and puma, the striped tiger and the spotted leopard
are simply cats of a larger growth whose remoter
ancestry is one with that of the previously cited forms.
Not until we explore and compare their several systems
do we see how thoroughgoing is their uniformity in
structural plan. And because reason justifies the view
regarding the origin of domestic cats from wild ances-
tors, the evolution of all the various members of the cat
tribe must be acknowledged. These animals exhibit
a fundamental likeness, which, to employ a musical
analogy, is the ^Hheme" of ^^cat-ness," and they are so
many variations of this theme.

The members of another tribe of the familiar car-
nivora display in their own way the same kind of evi-

38 DOCTRINE OF EVOLUTION

dences of relationship. The varieties of domesticated
dogs differ far more widely among themselves than do
common cats, yet their community of ancestry is
demonstrated not only by structural resemblances, but
also by the striking fact that forms as diverse as the
greyhound and the fox terrier can be crossed. Here
again there are wild forms, like the wolf and fox and
jackal, so like the domesticated members of the dog
tribe that we cannot fail to recognize a common '^dog-
ness" and its significance as evidence of the relationship
in ancestry of all these animals.

Extending our survey so as to include the other
tribes of flesh-eaters, identical principles come to light.
One is compelled to regard the polar and grizzly bears
as obvious blood relatives of the brown bear, and even
of the raccoon of our own territory. Instead of walking
upon their toes like cats and dogs, these animals plant
their feet flat upon the ground ; and they agree in many
other details of structure that place them together, but
somewhat apart from the other tribes. The many
kinds of seals and walruses and sea elephants form
still another group displaying similar bodily characters,
but differing more widely from the '^cat theme'' in
these differences. They are all true carnivora, but in
the course of their evolution they have progressively
changed so as to be adapted to life in the water where
they find their prey. The bones of the limbs are the
same in number and arrangement as in the cat's limb,
but the seal's anterior appendage or ^^arm" has altered
in numerous ways so as to become an efficient flexible
paddle, while the hind limbs have shifted posteriorly,
very much as screw propellers have evolved in the his-

STRUCTURE AND DEVELOPMENT 39

tory of steam vessels. How the members of the seal
tribe have changed in their descent from purely terres-
trial ancestors is partly explained by such intermediate
animals as the otter. This form is adapted by its
slender body and partly webbed feet to a semi-aquatic
life ; it seems to have halted at a point beyond which all
of the seals have passed in their evolution.

Each one of these tribes by itself provides conclusive
evidence of evolution, for it is most reasonable to regard
the 'Hheme" in every case as a product of common
inheritance, while the variations of any theme are best
understood as the results of adaptive changes in various
directions. But the examples have disclosed a larger
relation and a principle of wider scope, as indeed the
assignment of all these tribes to the single natural
group of the carnivora implies. These tribes are put
together because comparative anatomy finds that the
common characters of all cats are fundamentally like
those of all dogs and bears and seals, and in these com-
mon qualities the carnivora differ from all other mam-
malia. Does this mean that the branches which bear
respectively the various members of the several tribes
are outgrowths of a single limb of the evolving animal
tree ? Science does not hesitate to give an affirmative
answer, because, as in the case of the similar but vary-
ing domestic cats, no other explanation of tribal re-
semblance in structure seems so reasonable and natural.

So far the examples have been taken from one order
of the highest class of backboned animals, called mam-
malia. When our survey is extended to other divisions
of this class, additional laws of organic relationship are
discovered. If in a series of evolving generations the

40 DOCTRINE OF EVOLUTION

line of modification proceeding from a terrestrial animal
like a cat to semi-aquatic and marine types substan-
tially like an otter and a seal should be carried further,
it will inevitably lead to forms possessing characters
such as those displayed by whales and the related por-
poises, dolphins, and narwhals of the order cetacea. In
their make-up all of these animals clearly possess the
general characteristics of mammals, and they constitute
collectively another limb which has sprung from the
same stock as the carnivora, although at an earlier
time. This we believe because of their plan of body
and because their peculiar organization fits them even
more perfectly than the seals for aquatic existence that
is their only possible mode of life. In the case of the
whales the bony framework of the fore limb is again
like that of the cat's leg, although the whole structure is
a flexible finlike paddle. The hind limb has disap-
peared as an efficient organ, but the significant fact
is that small rudiments of hind hmbs are present just
where corresponding structures are placed in the seal.
These vestiges cannot be reasonabl}^ accounted for,
unless they are the degenerate hinder limbs of a remote
four-footed ancestor. Furthermore the young whale
possesses a complete coat of hair, which is afterwards
replaced by blubber; but hair is a thatchlike coat to
shed rain, as the way the hairs lie on a terrestrial mam-
mal indicates. We are therefore forced to conclude
that whales have originated from four-footed animals
walking about on land, because no opposed explana-
tion gives so reasonable an interpretation of the
observed facts.
Another group of famihar animals materially rein-

STRUCTURE AND DEVELOPMENT 41

forces the results already established. After what has
been said, it will not be difficult to perceive the meaning
of the resemblances among mice of the house and field,
and of rats and rabbits and squuTels. All of them
possess heavy curved gnav/ing teeth, or incisors, and
lack the flesh-tearing or canine teeth. They agree
in many other respects which distinguish them as a
separate natural order of the mammals called the
rodentia. Again we find a highly aberrant form in the
flying squirrel, which leads toward an order with another
plan of body. This animal is a true rodent, which
lengthens its leap from branch to branch by means of a
fold of skin stretching between its fore and its hind
limbs. It is an animated aeroplane, and it shows in
part how bats have originated. The wing of a bat is an
elastic membrane stretching not only between the two
legs of one side, but also between the greatly lengthened
*' fingers '^ of the fore limb. But the bones of arm, wrist,
and fingers are almost precisely the same in number
and relation as in walking forms. The fact that this
peculiar wing adheres to a plan belonging to the anterior
legs of walking or climbing types has no reasonable
explanation save that of evolution.

The well-known group of hoofed animals, including
horses and cattle, is also valuable for our present pur-
poses, as well as in a later connection when the evidence
of fossils is described. The elephant possesses five toes
armed with well-developed nails or hoofs. A tapir has
four or three toes, and it would seem that its ancestor
had had five toes, of which one or two had been lost.
A rhinoceros possesses three toes, and its foot is con-
structed internally like the elephant's with the outer

42 DOCTRINE OF EVOLUTION

elements absent. The horse comes last with one large
toe and hoof, but on either side of the main bones of
this digit are vestiges of what must have been toes in
its ancestors. Among the even-toed forms the hippopot-
amus has four which reach the ground, with a vestige
of a fifth, so this animal has apparently descended from
a typical mammal with the full number along a different
line from that taken by the odd-toed forms. A pig
has a cloven hoof, made up of what we may call the
third and fourth members of a series of five digits, but
the second and fifth fingers and toes are present,
though they are withdrawn from the ground so as to be
no longer functional; this animal seems to have pro-
ceeded further along the same line taken by the hippo-
potamus. A deer, with still smaller rudiments at the
sides of its double foot, leads in the comparative series
to the camel with a cloven hoof devoid of any such relics.
We must pass with only brief mention the lower orders
of mammalia, like the insect-eating forms to which
armadillos and ant-bears belong. Of greater interest
are the pouched mammals like the kangaroo and
opossums, which live almost exclusively in the Austrahan
realm. The kangaroo is endowed with a head somewhat
like that of a goat, and well-developed hind legs that
enable it to make leaps of astonishing length. Some
of its relatives, such as the bandicoot, are like rats, or
like bears, as in the case of the wombat. The Tas-
manian wolf is another true marsupial, even though
divergent adaptation has brought it to resemble the
carnivora of the dog tribe in general appearance and in
special structures like the teeth. Finally at the very
bottom of the mammalian scale are two small forms

STRUCTURE AND DEVELOPMENT 43

living in the Australian faunal region. The duckbill or
Ornithorhynchus is the better known animal, with its
close fur, webbed feet, and flattened ducklike beak,
while its only other near relative, the Echidna, is
somewhat similar to the spiny hedgehog in external
appearance. A unique peculiarity of these two forms
is that they produce eggs much like those of reptiles
and birds, and this fact, together with others of a
structural nature, brings the whole group of mammals
near to the lower classes of the Vertebrata.

Looking back on the several orders of mammals, it
will be seen that the last mentioned are much less
differentiated or specialized in their general organiza-
tion. Above the level of the egg-layers and the pouched
mammals, the higher orders branch out in different
directions and reach up to various levels of the scale
of animal organization.

The foregoing structural evidences of organic trans-
formation in the past histories of cats and seals and
whales insistently recall the analogies of the locomotive
and the ship employed at the outset. All these animals,
like the mechanical examples, have come to differ in
their derivation from the same original parents, and their
lines of descent have diverged so as to fit the products
of evolutionary modification to diverse circumstances.
Even the vestigial organs of animals have their counter-
parts in the machines. The cowcatcher was a large
and important structure in the early days of railroad-
ing, but it has become relatively useless with the
decrease of grade crossings and the construction of
more complete lines of fence. The structure still
persists, sometimes in a greatly reduced form. Even

44 DOCTRINE OF EVOLUTION

more obvious is the change of structure in the case of
masts of vessels, which originally bore the sails for
propelling the ship. When steam engines were em-
ployed to give motive power, masts did not disappear.
They now provide the derrick supports of trading
steamers ; in battleships their function is changed to
that of fighting tops and signal yards. Even the poles
carried by canal boats to bear windmills must be re-
garded as the reduced vestiges of masts originally con-
structed to carry sails ; and their adaptive evolution,
like that of countless structures in animals, has been
accomplished by degeneration.

The birds are another class of backboned animals
which exhibit identical principles of relationship. A
heron has long legs and wide-spreading toes, which
keep its body out of the water as it stalks about the
marshes where it seeks its food ; its bill is a long slender
pincers. Compare it with an eagle; the latter has a
short and heavily hooked beak to tear flesh, while its
stout legs bear strongly curved talons to hold its
struggling prey. Swimming birds like the swan and
duck and loon possess feet which are constructed in
general like those of the former examples, but they are
webbed and shortened to serve as paddles. In the
penguin we find a counterpart of the seal among
mammals ; its feathers are much reduced and its fore
limbs are no longer wings enabling the animal to fly,
but they are paddles which it uses when it swims in
pursuit of fish. Finally the ostrich and wingless bird
of New Zealand — the Apteryx — have wings that are

STRUCTURE AND DEVELOPMENT 45

useless vestiges, which, in the latter case, are hidden
under the brushhke feathers covering the body. It
is unnecessary to add more examples, for even these
few illustrations establish exactly the same principles
of relationship and evidences of evolution that are to
be found in the series of mammalia.

Reptiles also are grouped, like the mammals and birds,
as variations about a central theme. An ordinary lizard
is perhaps the nearest in form to the remote ancestor
from which all have sprung. Some lizards are long
and very slender, with all four limbs of greatly reduced
size. Others, which are still true lizards, have lost the
hind limbs, or even all the legs, as in the ^^ blind worms"
of England. One step more, and an animal which has
progressed further along a similar line of descent
would be a snake. Just as whales as a group are
derivable from forms which resemble types belonging
to another order, so snakes as an order are to be regarded
as more radically altered derivatives of some four-footed
lizardlike creature. Alligators are very much like
lizards in general form, and their order is a diverging
branch from the same Umb. Finally the evolution of
turtles from the same ancestors is intelligible if we begin
with a short stout animal like the so-called '^ horned
toad" of Arizona, and proceed to the soft-shelled
tortoise of the Mississippi River system ; the establish-
ment of a bony armor completes the evolution of the
familiar and more characteristic turtle.

Frogs and salamanders constitute another lower
class, called the amphibia, whose members are gilled
during the earlier stages of development. An adult
frog is essentially a salamander without a tail and

46 DOCTRINE OF EVOLUTION

with highly developed hinder limbs. The salamanders
differ as regards the number of fishlike gill clefts that
they all possess in their young stages, but which dis-
appear entirely or in part during later life. In com-
parison with the lizard as a typical reptile, a salamander
is more primitive in all of its inner organic systems,
while in its nearly continuous body, with head and tail
gradually merging into the trunk, it also displays a
somewhat simpler form of body.

The fishes are the lowest among the common verte-
brates, and they offer an abundance of independent
testimony as to the truth of the principles of compara-
tive anatomy. The common shark is perhaps the most
fundamental form, with a hull-like body undivided into
head, trunk, and tail, and from it have originated such
peculiar variations as the hammerhead and skate.
Among fishes with true bones, a cod or trout is the most
typical in general features. Without ceasing to be
true bony fishes, the trunk-fish and cow-fish are adapted
by their peculiar characters of spine and armor plate to
repel many enemies. The puff fish can take in a great
amount of water, when disturbed, so as to become too
large to be swallowed by some of its foes, illustrating
another adaptive modification for self-defense. The
wonderful colors and color patterns of the tropical
fish of the reef, or of the open water forms like the
mouse-fish of the Sargossa Sea, often render them more
or less completely hidden from the foraging enemy. A
flounder looks like a fish which was originally symmetri-
cal, but which had come to lie flat on its side upon the
bottom, whereupon the eye underneath had left its
original place to appear on the upper surface. The

STRUCTURE AND DEVELOPMENT 47

difficult and unusual conditions of deep-sea existence
have been met by fishes in two ways ; some forms
possess luminous frilled and weedlike fins, which
lure their prey to within easy reach of their jaws, while
others have enormous eyes, so as to make use of all
possible rays of light in their pursuit of food organisms.
But all of these diverse forms are true fishes, possessing
a common heritage of structure which demonstrates
their unity of origin.

The brief review of backboned animals has shown
how comprehensive are the principles of relationship.
The families and tribes of each order, such as the carniv-
ora, are like branches arising from a single limb ; the
orders in their turn exhibit common qualities of struc-
ture which mean that they have grown from the same
antecedents, while even the larger divisions or classes
of mammals, birds, reptiles, amphibia, and fishes, possess
a deep underlying theme whose dominant motif is the
backbone, which proves their ultimate unity in an-
cestry. The greater and lesser branches have reached
different levels, for the fish is clearly simpler in its
make-up than the highly specialized bird. But the
great fact is that structural evidences demonstrating
the reality of genealogical affinities are displayed by
the entire series of vertebrates ; although they differ
much or little in many or fewer respects they have one
and the same ground-plan.

The lower animals devoid of backbones, and there-
fore called invertebrates, are not so well-known except
to the student of comparative anatomy, because they

48 DOCTRINE OF EVOLUTION

are not so often met with, and because they are usually
very small or microscopic ; but in many respects their
importance to the evolutionist surpasses that of the
vertebrates. Their structural plans are far more
varied, and they range more widely from higher and
relatively complicated organisms to the unitary one-
celled animals. A knowledge of some of them is es-
sential for our present purpose, which is to learn how
sure is the basis for the principles of relationship and
how complete is the structural evidence of evolution.

Worms are represented in the minds of most people
by the common earthworm or sandworm. The body in
either case is made up of a series of segments or joints
which agree closely throughout the animal in external
appearance and in internal constitution. A section of
the digestive tract, a pair of nerve centers, two funnel-
like tubes for excretion, and similar blood vessels
occur in each portion.

Precisely similar features are displayed by the Crus-
tacea, which seem to be so different. Every one is
familiar with the appearance of lobsters and crabs.
Even in these animals the body is composed of segments,
but these are not like one another, nor are they freely
movable throughout the body. Five are fused in all
Crustacea to make a head ; in lower members of the
order the eight succeeding segments are free, but in
the lobster they are joined together and united with
the head. The hinder part of this animal is a long
abdomen whose segments remain more primitive and
independent. But in a crab, the whole plan has been
modified by the shortening and broadening of the
head-thorax, and by the reduction of the abdomen,

STRUCTURE AND DEVELOPMENT 49

which is also turned under the anterior part of the body.
The internal organic systems are constructed upon a
worm plan with modifications. Nearly every one of
the segments bears one pair of appendages, which can
be referred by their forked nature to the two-parted,
oarlike flaps of sandworms, but the appendages of
Crustacea have departed from their prototypes in
functional respects and in details of structure. They
are variously feelers, jaws, legs, pincers, and swimming
paddles, evolved to serve different purposes, just as
the limbs of the vertebrates we have described have
become variously arms, wings, flippers and paddles in
apes, bats, seals, and whales.

Butterflies, beetles, bees, and grasshoppers seem at
first sight to be entirely different, even though they
agree in being more or less segmented. But all of them
have heads with four pairs of appendages of the same
essential plan, middle thoracic regions of three segments
more or less united, bearing three pairs of legs and
usually two pairs of wings, while the hinder part is a
freely jointed abdomen without real limbs. In these
respects the countless varieties of insects agree so that
they also like Crustacea of various kinds seem to have
been derived from wormlike animals with more simply
segmented bodies. Indeed spiders and scorpions and
their relatives of the group arachnida prove for similar
reasons to be derivatives of the same original stock,
and own cousins of the insects.

In nearly every one of the invertebrate branches we
find representatives which interest us chiefly because
they appear to have reached their present condition
by retrograde evolution. Barnacles are really crus-

E

50 DOCTRINE OF EVOLUTION

tacea, but they have lost their eyes as well as some
other structures that are most useful in animals with
a free existence, because they have adopted a fixed
mode of life, which has also brought about the loss
of the original freely jointed character of the body.
A tapeworm as an example of internal parasites is
an extremely degenerate form which lacks a digestive
tract, because this is superfluous in an animal which
lives bathed in the nutrient fluids of its host. Compar-
ing it in other respects with other low wormlike crea-
tures, it appears to be a relative of peculiar simple worms
with complete organization and independence of life.
All these degenerate forms enlarge our conception of
adaptation by adding the essential point that progress
is not always the result of evolution. Indeed we have
learned this in the case of vestigial and rudimentary
structures of higher forms like whales, and now we find
that entire animals may degenerate as a result of
changes no less adaptive than progressive modifications.
Passing by other invertebrate groups made up of
species arranged like higher animals in smaller and
larger branches according to their degree of fundamental
similarity, we arrive at a place in the scale occupied
by two-layer animals without the highly developed
and clearly differentiated organic systems of the forms
above. The fresh- water animal Hydra exemplifies
the creatures of this level, where also we find sea-
anemones and the soft polyps which form corals and
coral reefs by their combined skeletons. Hydra is an
animal to which we must return again and again as we
study one or another aspect of organic evolution. In
general form it is a hollow cylinder closed at one end,

STRUCTURE AND DEVELOPMENT 51

by which it attaches itself, while at the upper end,
surrounded by a group of tentacles, is the mouth which
leads to the central cavity. The wall of this simple
body is composed of two layers of cells, between which
there is a gelatinous layer rarely invaded by cells. The
inner layer lines the central space into which food
organisms are thrust by the tentacles, and it is con-
cerned primarily with digestion. The outer layer
comprises cells for protection and sensation prima-
rily. Cells of both layers have muscular prolongations
which by their operation enable the whole animal to
change its form and to move from one place to another.

It may seem that such an animal is totally unlike
any of the higher and more complex types. In certain
respects, however, it is identical with the other forms
inasmuch as it performs all of the eight biological tasks
demanded by nature. It is also similar in so far as
its inner layer, like the innermost sheet of cells in
higher forms, is concerned with problems of taking
and preparing food, while the protective outer layer re-
sembles in function the outermost covering of all animals
higher in the scale. Beyond these a still more funda-
mental agreement is found in its cellular composition.

At the lower end of the animal scale are organisms
which consist of one cell and nothing more. Amoeba,
to which we must refer again and again, is an example
of this group which possesses an overwhelming impor-
tance to the comparative student because the origins
of all the characteristics of animals higher in the scale
are to be found within it. Amoeba itself is a naked
mass of protoplasm, about j^-^ of an inch in diameter,
enclosing a nucleus. Its form is not constant during

52 DOCTRINE OF EVOLUTION

activity, for fingerlike processes called pseudopodia
are pushed out tentatively in many directions to be
followed as circumstances direct by the materials of
the whole cell body. Other protozoa differ in possessing
constant forms, or in having constant vibratile pro-
cesses, or shells of some kind, while in still other cases
like individuals combine to make colonies which are
more or less definite and permanent. Here at the very
foot of the organic scale are found animals which seem
to be entirely different from those above. Upon
examination they, like Hydra, prove to be the same as
regards the number and kind of functions they perform,
but in structural regards their evolutionary relation
to all higher animals is indicated solely by the fact
that they are cells composed of protoplasm. Never-
theless the principle which states that resemblance
means consanguinity still holds true, for cellular con-
stitution is a unique possession of things of the living
world, — something which demonstrates the common
origin of all living things just as truly as the ^^cat-ness"
of our first series of examples reveals for a smaller
group the significance of likeness and the nature of
the basic law of comparative anatomy.

Employing a figure of speech, we have climbed down
the animal tree from the higher regions where the
mammals belong. Having reached the very foot of
the trunk we are in a position to review and summarize
the evidences which we have discovered all about us
as we have descended. The various examples we
have mentioned and the groups to which they belong

STRUCTURE AND DEVELOPMENT 53

clearly occupy different places in the scale which begins
with the protozoa and extends upward to the most
complicated and differentiated animals. Hydra takes
its place above the protozoa for obvious structural
reasons ; worms belong to a still higher zone, surpassed
by the more complex jointed animals like Crustacea
and insects. Far above these are the vertebrates,
among which we have already demonstrated the occur-
rence of different grades of organization, from the fish
up to the higher amphibia and reptiles, and beyond
in two directions to the diverging birds and mammals.
The basic characteristics of every group in a high
position may be traced back to some one or another
of the divisions at a lower level, so that the general
sequence of the structural levels from low to high
becomes intelligible as the order of their evolution.

To my mind the rudimentary and vestigial structures
of animals are in themselves proof positive of a natural
history of change. The few illustrations can be re-
inforced by countless examples offered by every group
of living animals. If such structures have not evolved
naturally by degenerating from more efficient counter-
parts in ancestors of earlier times, and if they have
been specially created, they are utterly meaningless
and their very existence is unreasonable. If common
sense is to be employed, they demonstrate evolution.

Everywhere throughout the whole series animals
place themselves in a treelike arrangement, for in their
respective levels they occur like leaves at the ends of
the lines of descent which have led up to them and
which are comparable to the branches and limbs
arising from the trunk of a tree. Thus the major

54 DOCTRINE OF EVOLUTION

and minor divisions of animals do not follow in the
order of the rungs of a ladder, even though they must be
assigned to different levels according to the complexity
of their construction. The summary given above,
namely, that the occurrence of lower and higher levels
reveals an order of evolution, is amplified and not con-
tradicted by the statement that the species of animals
are grouped in a treeHke arrangement. It is the task
of the evolutionist, provided with all the facts of com-
parative anatomy and deahng only with the various
species as separate leaves, so to speak, to reconstruct
the now invisible but not unreal twigs and branches
and limbs of the animal tree, and to show how they have
diverged at one time or another as they have grown
and spread to produce the species of the present day.
This he may do in so far as he may find sufficient
materials to enable him to employ the methods of
comparative anatomy and the great natural principle
established by this method — that essential likeness
means consanguinity.

No evidence of evolution could be more significant
and interesting than the results provided by the com-
parative study of development. In the first place it is
an obvious fact that every living thing changes in the
course of its life-history, and if as an adult it occupies
a high place in the animal scale, its embryological trans-
formation is more elaborate and intricate than in the
case of a lower form. Every one knows that organisms
do develop, and yet I believe that few appreciate the
tremendous significance of the mere fact that this is

STRUCTURE AND DEVELOPMENT 55

true, while still fewer are aware that the peculiar
and characteristic early stages through which an
animal passes in becoming an adult are even more
striking than the fact of development itself. We shall
learn something of these earlier conditions in the
development of some of our most familiar animals,
but at the outset nothing can be more important than
an appreciation of the first great lesson of this depart-
ment of natural history — namely that organic trans-
formation is real and natural. We do not need to
employ the methods of formal logic to know that in
growing up a human infant undergoes the changes
of childhood and adolescence, that kittens become cats,
and that an oak tree is produced by an acorn, for we
know these things directly by observing them. It is
natural for development to take place under normal
conditions, and if it does not, then something has inter-
fered with nature. Inasmuch as ''growing up" is
accomplished by the alteration of an organic mechanism
with one structure into an individual with a changed
plan of body, it is in essence the actual process of
evolution which the comparative study of grown ani-
mals of to-day demonstrates in the way we have
learned. The study of animal structure discovers
the process of evolution because the most reasonable
interpretation of the similarities and minor differences
exhibited everywhere by the various groups of animals
is that descent with adaptive and divergent modification
has taken place ; the result is reached by inference,
it is true, but by scientific and logical inference.
With development it is otherwise. No reasoning is
necessary to tell us that organic transformation is

56 DOCTRINE OF EVOLUTION

a real and a natural process. We see it everywhere
about us and we ourselves have come to be what we
are by a natural history of change. Can we consistently
deny that it is possible for a species to alter in the long
course of time when a few brief weeks are sufficient for
the new-laid egg of the fowl to develop into a fledgling ?
Many indeed strain at the gnat of the longer process
in the past when without hesitation they recognize the
real and obvious fact of individual development in a
brief period.

I have said that development is a ^'natural" process.
We employ this word for the familiar and everyday
occurrence or thing ; it does not imply that everything
is known about the object or phenomenon, because
science knows that complete and final knowledge is
impossible. We say that it is natural for rain to fall
to the earth, and we speak of the law of gravitation
according to which this takes place as a natural prin-
ciple, but it may not have occurred to many to inquire
what makes rain fall and why do masses of matter
everywhere behave toward one another in the consistent
manner described by the law in question. Sunshine
is natural, but we do not know why light travels as it
does from the sun to the earth, and this is another
question which, like the inquiry into the ultimate cause
of the familiar and natural phenomenon of gravitation,
has not yet been answered. But it is still regarded as
natural for the rain to fall and for the sun to shine.
In the same way does science view development, de-
noting it natural because it is an ordinary everyday
matter. And we are under no more obligation to postu-
late supernatural control for the changing forms in the

STRUCTURE AND DEVELOPMENT 57

life-history of a chick or a cat than we need to assume
that gravitation and the radiation of hght demand
immediate supernatural direction. The embryology
of no form is fully understood or described or explained,
but no intelHgent person would be wiUing to assert
that because complete knowledge is lacking, it is
unnatural for organic transformation to take place
during growth. Whatever may be the ultimate origin
and nature of the directing powers behind gravitation
and development and other phenomena, we have
no concern with such matters because they cannot be
handled by scientific methods and one belief about them
is on the same plane with any other. Our task is to
deal with the everyday phenomena of life and the
production of living species.

It is not necessary to go far afield to find an animal
which will introduce us to the general principles of
embryology. In the present instance as in the case
of comparative anatomy almost any form will disclose
the meaning of development, for animate nature is
uniform and consistent in its methods of operation
throughout its wide range. We shall begin with the
familiar frog which every one knows is a product of a
tadpole ; passing on to the chick we will learn more facts
that will enable us to formulate the main principle of
comparative embryology in definite terms ; we will then
be prepared to extend our survey so as to include some-
what less familiar facts and animals that are even more
significant than the first illustrations.

If we should visit a woodland pond in early spring, we

58 DOCTRINE OF EVOLUTION

would find somewhere among the leaves and sticks in
the water large masses of a clear jellylike consistency
enclosing hundreds of little black spheres about an
eighth of an inch in diameter. These are the egg
masses and eggs of a common frog. Watching them
day by day we see the small one-celled egg spheres
divide into more and more numerous portions which
are the daughter-cells, destined to form by their prod-
ucts the many varied tissues and organs of the develop-
ing larva and adult frog. After three or four days the
egg changes from its globular form into an oval or
elliptical mass, and from one end of this a small knob
projects to become a flattened waving tail a few days
later. On the sides of the larger anterior portion
shallow grooves make their appearance and soon break
through from the throat or pharynx to the exterior as
gill-slits. Shortly afterwards the little embryo wriggles
out of its encasing coat of jelly, develops a mouth, and
begins its independent existence as a small tadpole, with
eyes, nasal and auditory organs, and all other parts that
are necessary for a free life. Thus the one-celled egg
has transformed into something that it was not at first,
and in doing this it has proved the possibility and the
reality of organic reconstruction.

The tadpole breathes by means of its gills, and it is
at first entirely devoid of the lungs which the adult
frog possesses and uses. When we speak of the larval
respiratory organs as gills we imply that they are hke
the organs of a fish which have the same name ; they
are truly like those of fishes, for the blood-vessels
which go to them are essentially the same as in the lower
types and they are supported by simple skeletal rods

STRUCTURE AND DEVELOPMENT 59

like the gill-bars of the fish. In a word, they are the
same things.

The animal feeds and grows during the months of
its first summer, and hibernates the following winter;
with the warmth of spring it revives and proceeds
further along the course of its development. Near
the base of the tail two minute legs grow out from the
hinder part of the body, and while these are enlarging
two front legs make their appearance a little behind the
gills. The tadpole now rises more frequently to the
surface where it takes small mouthfuls of air. Mean-
while great changes are effected inside the body where
the various systems of fishlike organs become remodeled
into amphibian structures. A sac is formed from the
wall of the esophagus, and this enlarges and divides
to form the two simple lungs. The legs increase in
size, the tail dwindles more and more, the gills close up,
and soon the animal hops out on land as a complete
young frog. From this time on it breathes by means
of its lungs instead of gills, even though it returns to
the water to escape its foes, to seek its prey, and to
hibernate in the mud of the lake bed during the winter
months.

All these changes are familiar and natural, but until
science places them and similar facts in their proper
relations their significance is lost to us. The tadpole is
essentially a fish in its general structure and mode of
life, even though its heritage is such that it can develop
into a higher animal. When it does become a frog it
proves beyond a doubt that there is no impassable
barrier between fishes and amphibia. Our earlier com-
parison of the structures of these two classes of verte-

60 DOCTRINE OF EVOLUTION

brates led to the conclusion that the latter had evolved
from antecedents like the former, and had thus followed
them upon the earth ; now that sequence seems to have
some connection with the method by which a tadpole,
obviously not a fish but nevertheless actually fishlike,
changes into a frog, a member of a higher class of verte-
brates. This method is employed by developing frogs
apparently because it follows the ancestral order of
events, and because, so to speak, the only way a frog
knows how to become a frog is to develop from an egg
first into a fishlike tadpole and then to alter itself as
its ancestors did during their evolution in the past.
We begin to see, then, that in addition to the impressive
fact of development itself, the mode of organic trans-
formation is far more conclusive evidence of evolution,
because it reveals an order of events which parallels
the order established by comparative anatomy as the
evolutionary sequence.

However it is well to review some of the changes
by which a chick comes into existence before attempt-
ing to comprehend fully the fundamental principle
of development that the tadpole's history discloses to
us. The egg of a common fowl is certainly not a chick.
Within the calcareous shell are two delicate membranes
that enclose the white or albumen ; within this, swung
by two thickened cords of the albumen, is the yellow
yolk ball enclosed by a proper membrane of its own.
In the earliest condition, even before the albumen and
the shell are added and before the egg is laid, on one
side of the yolk-mass there is a tiny protoplasmic spot
which is at first a single cell and nothing more. The
hen's egg is relatively enormous, but nevertheless, like

STRUCTURE AND DEVELOPMENT 61

that of the frog, it starts upon its course of development
as a single unitary biological element — a cell. During
the earliest subsequent hours the first cell divides again
and again to form a small disk upon the surface of the
yolk. Soon the cells along the middle line of this small
sheet become rearranged to make an obvious streak
or band, and about this line a simple tube is constructed
which is destined to become the future brain and
spinal cord. The whole disk continues to enlarge by
further division of its constituent elements so that it
encloses more and more of the yolk mass, but the little
chick itself is made out of the cells along the central
line of the original plate, from which it folds at the sides
and in front and behind so as to lie somewhat above
and apart from the flatter enclosing cell layers which
partly surround the yolk.

At the sides of the primitive nerve-tube small blocks
of cells arise to develop into primitive muscles and other
structures. As nourishment is brought to the embryo
from the surrounding layers enclosing the nutrient
yolk, one system after another takes its shape and
builds its several parts into organs which can be rec-
ognized as elementary structures of a chick. Among
the more interesting ones are small clefts or slits formed
in the side walls of the rudimentary throat or pharynx.
Blood-vessels go forward from the simple heart to run
up through the intervening bars exactly as in the tadpole
and the fish. In brief, the young chick possesses a
series of gill-slits, for these structures are the same in
essential plan and relations as the clefts of tadpoles and
fishes. Does this mean that even birds have descended
from gill-breathing ancestors? Science answers in

62 DOCTRINE OF EVOLUTION

the affirmative, because evolution gives the only reason-
able explanation of such facts as these. The case
seems different from that of the frog, because gills
are used by the tadpole, but gill-slits and gill-bars can
have no conceivable value for the chick as organs
concerned with the purification of the blood. None
the less, if the transition from a gilled tadpole to the
adult with lungs means an evolution of amphibia from
fishlike ancestors, then the change of a chick embryo
with gill-clefts into the fledghng without them is most
reasonably interpreted as proof that birds as well as
amphibia have had ancestors as simple as fishes.

As development progresses four small pads make
their appearance; two of these lie on either side of
the body back of the head and the other two arise near
the posterior end. They are far from being wings and
legs, but as day follows day they become molded into
somewhat similar limbs, as much alike in general plan as
the four legs of a lizard ; subsequently the ones at the
front change into real wings and the hinder ones be-
come legs. Meanwhile the internal organs slowly trans-
form from fishlike structures into things that display
the characteristics of reptilian counterparts, and only
later do they become truly avian. Last of all the finish-
ing touches are made, and the whole creature becomes a
particular kind of a bird which picks its way out of
the shell and shifts for itself as a chick.

Only a few of the countless details have been men-
tioned which demonstrate the resemblance of the
successive stages first to fishes, and later to amphibia
and reptiles. We have a wide choice of materials,
but even the foregoing brief list of illustrations shows

STRUCTURE AND DEVELOPMENT 63

that the order in which the stages follow is the one
which comparative anatomy independently proves to
be the order of the evolution of fishes, amphibia, rep-
tiles, and birds. Why, now, should it be necessary for
a developing bird to follow this order? The answer
has been found in the immense array of embryological
facts that investigators have verified and classified,
that all tell the same story. It is, that birds have
arisen by evolution from ancestors which were really
as simple as the members of these lower classes. It
seems then that the only way a bird of to-day can
become itself is to traverse the path along which its
progenitors had progressed in evolution. Stating its
conclusions precisely, science formulates the principle
in the following words : individual development is a
brief resume of the history of the species in past timeSj
or, more technically, ontogeny recapitulates phytogeny.
To be sure, the full history is not reviewed in detail,
for the chick embryo does not actually swim in water
and breathe by means of gills. Only a condensed
account of evolution of its kind is presented by an
embryo during its development ; as Huxley and
Haeckel have put it, whole lines and paragraphs and
even pages are left out; many false passages of a
later date are inserted as the result of peculiar larval
and embryonic needs and adjustments. But in its
major statements and as a general outline, the account
is a trustworthy natural document submitted as evi-
dence that higher species of to-day have evolved from
ancestors which must have been like some of the present
lower animals.

Coming now to the mammalia, it might seem that

64 DOCTRINE OF EVOLUTION

we have reached forms so highly developed that they
would not exhibit the same kind of developmental
history, but would have their own mode of growing up.
This is not so, for like the adult fish, the larval tadpole,
and the embryo chick, an embryo of a cat or a man
is at one time constructed with a series of gill-clefts
and with blood-vessels and skeletal supports of fishlike
nature that are everywhere associated with gills.
The embryos of wildcats and dogs, rabbits and rats,
pigs, deer, and sheep, and of all other mammalia, possess
similar structures. Thus they all pass through a stage
which is found also in the development of reptiles,
birds, and amphibia, — a stage which corresponds to
the fish throughout its life. Unless these facts mean
that the great classes of vertebrates have originated
together from the same or closely similar ancestors,
they are unintelligible ; for we cannot see why a cat or
a chick should have to be essentially fishlike at any
time unless this is so. Comparative anatomy states
as we have learned that the amphibia as a class have
evolved from and have out-developed the fishes, that
reptiles have progressed still higher, and that birds
and mammals have originated from reptilian ancestors
along roads that have diverged beyond the immediate
parent class. Because the members of each class have
to pass along the same path trodden by their many
varied ancestors, although at express speed, as it were,
the similarity of the earliest stages in their develop-
ment is explained, for during these periods they are
traversing a path over which their ancestors passed
together.
The places where the developing embryos depart

STRUCTURE AND DEVELOPMENT 65

from the common mode show where the several divi-
sions took leave of one another in their evolution, —
a point that comes out with great clearness when the
facts of mammalian development are broadly com-
pared. The embryos of carnivora and rodents and
hoofed animals are alike in their earlier develop-
ment, and their agreement means a community of
origin. At a certain point the cat and dog depart
from the common mode, but they remain alike up to a
far later stage than the one in which they are similar
to the embryos of rats and sheep. The rat and
squirrel and rabbit, on their part, remain together
until long after they take leave of the carnivora and
ungulates; while the sheep and cattle and pigs have
their own branch line, which they follow in company
after leaving the embryos of the other orders. The
reasons for these facts seem to be that the members
of the three orders exemplified have evolved from the
same stock, which accounts for their embryonic simi-
larity for a long time after they collectively come to
differ from amphibia and reptiles, while the members
in each order became differentiated only later, where-
fore their embryonic paths coincide for a longer period.
Thus the degree of adult resemblance which indicates
the closeness of relationship corresponds with the de-
gree of embryonic agreement ; that is, the cat and dog
are much alike and their modes of development are
essentially the same to the latest stages, while the cat
and horse agree only during the earliest and middle
stages, and their lines diverge before those of the cat
and dog on the one hand, or those of the horse and
pig on the other.

66 DOCTRINE OF EVOLUTION

Like the fundamental principle of comparative anat-
omy in its sphere, the Law of Recapitulation, formu-
lated as a summary description of the foregoing and
similar facts, is one that holds true throughout the en-
tire range of embryology and for every division of the
animal series, however large or small. We have dis-
cussed its broader application, and now we may take
up some of the more or less special cases mentioned in
the earlier section of the present chapter, to see how it
may work in detail.

The flounder was noted as a variant of the fish theme
which seemed to be a descendant of a symmetrical
ancestor because its structural plan was like that of
other bony fishes. If this be true, and if in its develop-
ment a flounder must review its mode of evolution
as a species, the young fish ought to be symmetrical;
and it actually is. The grotesque skate and hammer-
head shark were demonstrated to be derivatives of
a simpler type of shark ; their embryos are practically
indistinguishable from those of ordinary dogfish and
sharks.

Among the jointed animals a wealth of interesting
material is found by the embryologist. All crabs
seemed to be modified lobsterlike creatures ; to confirm
this interpretation, based solely upon details of adult
structure, young crabs pass through a stage when to all
intents and purposes they are counterparts of lobsters.
Even the twisted hermit crab, which has a soft-skinned
hinder part coiled to fit the curve of the snail shell
used as a protection, is symmetrical and lobster-like
when it is a larva.

Among the insects many examples occur that are

STRUCTURE AND DEVELOPMENT 67

already familiar to every one. The egg of a common
house-fly hatches into a larva called a maggot ; in this
condition the body destined to become the vastly differ-
ent fly is composed of soft-skinned segments very much
alike and also similar to the joints of a worm. Com-
parative anatomy demonstrates that the fly and all
other insects have arisen from wormlike ancestors,
whose originally similar segments later differentiated
in various ways to become the diverse segments of adult
insects ; the embryonic history of flies of to-day corrob-
orates these assertions, in so far as every individual fly
actually does become a wormlike larva before it changes
into the final and complete adult insect. The other
kinds of insects are equally striking in their hfe-his-
tories. All beetles, such as the potato bug and June
bug, develop from grubs which, like the maggots of flies,
are similar to worms in numerous respects. Butterflies
and moths pass through a caterpillar stage having even
more striking resemblances to worms. All the larvse of
insects are therefore like one another, and like worms
also, in certain fundamental characters of internal and
external structure; so the conclusion that the whole
group of insects has arisen by evolution from more
primitive ancestors resembling the worms of to-day is
based upon mutually explanatory details of compara-
tive anatomy and embryology.

Let us now turn back to some of the earlier pages of
the embryological record which we passed over in order
that we might translate the later portions dealing with
more familiar and inteUigible structures hke gills. Be-

68 DOCTRINE OF EVOLUTION

fore the egg of the frog becomes an elHptical mass of
cells, it is at one time a double-walled sac enclosing a
central cavity; in this stage it is called a gastrula.
Tracing back the mode of its formation, we find that it is
produced from a hollow sphere of fewer cells that are
essentially alike; this stage also is so important that
the special term hlastula is applied to it. Still earlier,
there are fewer cells — 128 or thereabouts, 64, 32, 16,
8, 4, 2, and 1. In other words, the starting point in
the development of the frog is a single biological unit;
this divides and its products redivide to constitute the
many-celled blastula and the double-walled gastrula.
All the other animals we have mentioned begin like
the frog, as eggs which are single cells and nothing more ;
they too pass on to become blastulse and gastrulae,
similar to those of the frog in all essential respects,
particularly as regards the nature of the organs produced
by each of the two primary layers, and the mode of their
formation. Does the occurrence of blastulse and gas-
trulae and one-celled beginnings mean that the higher
animals composed of numerous and much differentiated
cells have evolved in company from two-layered saccular
ancestors which were themselves the descendants of
spherical colonies of like cells, and ultimately of one-
celled animals ?

Comparative anatomy has asserted that this is so,
as we have already learned, for it finds that adult ani-
mals array themselves at different levels of a scale
beginning at the bottom with the protozoa, continuing
on to the two-layered animals like Hydra and jelly-
fish and sea-anemones, and then extending upwards to
the region of the more complicated invertebrates and

STRUCTURE AND DEVELOPMENT 69

vertebrates. It was difficult perhaps to believe that
these successive grades of organic structure indicated
an order of evolution, because it seemed impossible
that an animal so simple as a protozoan could produce
offspring with the complex organization of a frog or a
cat, even in long ages. But development delivers its
evidence relating to this matter with telling and im-
pressive force. How can we doubt the possibility of
an evolution of higher animals from ancestors as simple
as Hydra and Amoeba when a frog and a cat, like all
other complicated organisms, begin individual existence
as single cells, and pass through gastrula stages ? If we
deny it, we contradict the evidence of our senses, for
the development is actually accomplished by the trans-
formation of a single cell into a double-walled sac, and
of this into different and more intricate organic mechan-
isms. The process can take place, for it does take place.
Not until the investigator becomes familiar with a wide
range of diverse animals and the peculiar qualities of
their similar early stages, can he estimate the tremen-
dous weight of the facts of comparative embryology.
Were the statement iterated and reiterated on every
page and in every paragraph, there would be no undue
emphasis put upon the astounding fact that the appar-
ently impassable gap between a one-celled animal like
Amoeba and a mammal like a cat is actually compassed
during the development of the last-named organisms
from single cells. The occurrence of gill-slits in the
embryos of lizards, birds, and niammals now seems a
small thing when compared with the correspondences
disclosed by the earliest stages of development. But
in spite of their complexity, all the changes of '^ growing

70 DOCTRINE OF EVOLUTION

up" are explained and understood by the simple for-
mula that the mode of individual development owes its
nature primarily to the hereditary influence of earlier
ancestors back to the original animals which were
protozoa.

Embryology as a distinct division of zoology has grown
out of studies of classification and comparative anatomy.
Its beginnings may be found in medieval natural his-
tory, for as far back as 1680 Harvey had pointed out
that all living things originate from somewhat similar
germs, in the dictum '^Omne vivum ex ovo." By the
end of the eighteenth century many had turned to the
study of developing organisms, though their views by no
means agreed as to the way an adult was related to the
egg. Some, like Bonnet, held that the germ was a
minute and complete replica of its parent, which simply
unfolded and enlarged like a bud to produce a similar
organism. Even if this were true, Httle would be gained,
for it would still remain unknown how the germinal
miniature originated to be just what it was conceived
and assumed to be. Wolff was the originator of the
view that is now practically universal among natural-
ists, namely, that development is a real process of
transformation from simpler to more complex condi-
tions.

The subject of comparative embryology grew rap-
idly during the nineteenth century as the field of com-
parative anatomy became better known, and when
naturalists became interested in animals, not only as
specific types, but also as the finished products of an

STRUCTURE AND DEVELOPMENT 71

intricate series of transformations. When life-histories
were more closely compared, the meaning of the resem-
blances between early stages of diverse adult organisms
was read by the same method which in comparative
anatomy finds that consanguinity is expressed by re-
semblance. The great law of recapitulation, stated in
one form by Von Baer and more definitely by Haeckel
in the terms employed in the foregoing sections, was for
a time too freely used and too rigidly applied by natu-
rahsts whose enthusiasm clouded their judgment. A
strong reaction set in during the latter part of the nine-
teenth century, when attention was directed to the
anachronisms of the embryonic record and to the
alterations that are the results of larval or embryonic
adaptation as short cuts in development. Neverthe-
less, it is not seriously questioned, I believe, that the
main facts of a single life-history owe their nature to
the past evolution of the species to which a given animal
belongs.

Nowadays the problems in this well-organized de-
partment are concerned not only with more accurate
accounts of the development of animals, but also with
the mechanics of development, with the relative value of
external and internal influences, and above all with the
physical basis of inheritance. It is clear that the
factors that direct the development of a wood frog's
egg so that it becomes a wood-frog and not a tree-toad
must lie in the egg itself, as derivatives from the two
parent organisms. Weismann and his followers have
proved that a peculiar substance in the nuclei of the
egg and its daughter-products contains the essential
factors of development, whatever these may be. Ex-

72 DOCTRINE OF EVOLUTION

periments dealing with the phenomena of heredity
in pure and mixed breeds have largely confirmed Weis-
mann's doctrine, and they have prepared the way for
a deeper investigation of the marvelous process of
biological inheritance.

However much he may be interested in the details of
embryological science, the general student of natural
history is more concerned with the bearing of its pri-
mary laws upon the great problem of evolution. In the .
foregoing brief review of the fundamental facts and
principles of this subject, the purpose has been to show
how the phenomena of development are viewed by men
of science, and how they take their place in the doctrine
of organic evolution. And it has also been made plain
that comparative anatomy and comparative embry-
ology support and supplement one another in countless
ways and places, although each in itself is a complete
demonstration that evolution is a real and a natural
process.

Ill

THE EVIDENCE OF FOSSIL REMAINS

Few natural objects appeal to the interest and imagi-
nation of the student with more force than the frag-
ments of animals and plants released from the rocks
where they have been entombed for ages. Our lives
are so brief that it is impossible for us to comprehend
the full duration of the slow process which constructed
the burial shrouds of these creatures of long ago. We
try to picture the earth and its inhabitants as they were
when lizards were the highest forms of animals, and we
wonder how life was lived in the dense forests of the
coal age. Science can never learn all about the ancient
history of the earth and of the organisms of bygone
times ; yet it has been able to accomplish much through
its endeavors to reconstruct the past, for its method is
one by which sure results can always be obtained when-
ever there are definite facts with which it can work.
In our present study of evolution we reach the point
when we must examine the testimony of the rocks, and
the results and methods of that department of knowledge
called palaeontology, which is concerned with fossils and
their interpretation.

The word '^ palaeontology" means hterally the '^sci-
ence of living things of long ago." It deals directly
with the remains of animals and plants found as fossils,

73

74 DOCTRINE OF EVOLUTION

and it interprets them through its knowledge of the
way modern animals are constructed and of the changes
the earth's crust has undergone. A skull-like object
may be found in a coal field and may come into the hands
of the palaeontologist : from his acquaintance with the
head skeletons of recent types he will be able to assign
the extinct creature which possessed the skull to a defi-
nite place in the animal scale and to understand its
nearer or wider affinities with other animals of later
times and of earlier epochs. In doing these things
palaeontology employs the methods of comparative
anatomy with which we have now become familiar.
In the performance of its other tasks, however, palaeon-
tology must work independently. It is necessary to
know when a fossilized animal lived, not that its time
need be measured by an absolute number of a few
thousands or millions of years antedating our own era,
for that is impossible. But the important thing is to
know its relative age, and whether it preceded or
followed other similar animals of its own group or of
different divisions. The rocks themselves must be
understood, how they have been formed and how they
are related in mineralogical nature and in historical
succession. Palaeontology also deals with a number of
subjects that are not in themselves biological, such as
the combination of circumstances necessary for the
adequate preservation of fossil relics. In so far as it is
concerned with physical matters, as contrasted with
strictly biological data, it is one with geology. Indeed,
the investigators in these two departments must always
work side by side and render mutual assistance to one
another in countless ways, for each division needs the

EVIDENCE OF FOSSIL REMAINS 75

results of the other in order to accomphsh its own dis-
tinct purposes. It must be evident to every one that it
is impossible to understand the meaning of fossils and
the place of the testimony of the rocks in the doctrine
of evolution without knowing much about the geological
history of the earth and the influences at work in the
past. For these reasons palaeontology differs somewhat
from the other divisions of zoology where direct observa-
tion gives the materials for arrangement and study;
in this case the individual data, that is, the fossil frag-
ments themselves, can be made available only through a
knowledge of their exact situations, of the reasons for
their occurrence in particular places in the rock series
and of the way rocks themselves are constructed and
worked over by natural agencies. Our task is there-
fore twofold : certain physical matters of a geological
nature must first be investigated before the biological
facts can be described.

No doubt most people feel justified in believing that
the whole doctrine of evolution must stand or fall
according to the cogency of the palseontological evi-
dences. Plain common sense says that the owners of
shelly or bony fragments found in the deeply-laid
strata of the earth must have lived countless years
ago, and if the evolutionist asserts that primitive or-
ganic forms of ancient times have produced changed
descendants of later times, it would seem that fossil
evidence would be supremely and overwhelmingly
important. It is true, of course, that this evidence is
peculiarly significant, because in some ways it is more
direct than that of the other categories already outlined.
But it must not be forgotten that the doctrine is already

76 DOCTRINE OF EVOLUTION

securely founded upon the basic principles of anatomy
and embryology. Science must treat the data of this
category by different methods and must view them in
different ways. Therefore we are interested in palaeon-
tology because of the way it tells the story of evolution
in its own words, and because we are justified in expect-
ing that its account should include a description of some
such order of events as that revealed by the developing
embryos of modern organisms and that demonstrated
by the comparative anatomy of the varied species of
adult animals.

It is true that palaeontology gives direct testimony
about the evolutionary succession of animals in geo-
logic time. But we now know that embryology is
even more direct in its proof that organic transformation
is natural and real; while at the same time there is a
completeness in the full series of developmental stages
connecting the one-celled egg with the adult creature
that must be forever lacking in the case of the fossil
sequence of species. If paragraphs and pages are
missing from the brief embryonic recapitulation, whole
chapters and volumes of the fossil series have been lost
for all time. The investigators whose task it has been
to decipher the story of the earth's evolution have had
to meet numerous and exasperating difficulties which
do not confront the embryologist and anatomist who
study living materials. Nevertheless the library of
palseontological documents is one which has been
founded for over a century, and it has grown fast dur-
ing recent decades, so that consistent accounts may now
be read of the great changes in organic life as the earth
has altered and grown older. And in all this record,

EVIDENCE OF FOSSIL REMAINS 77

there is not a single line or word of fact that contradicts
evolution. What definite evidence there is tells uni-
formly in favor of the doctrine, for it is possible, in the
first place, to work out the order of succession of many
of the great groups of animals, and this order is found
to be the same as that established by the other bodies
of evidence. Secondly, some fossil groups are aston-
ishingly complete, so that the ancient history of a form
like the horse can be written with something approaching
fullness. Finally, the remains of certain animals have
been found so situated in geological ways, and so con-
structed anatomically, that the zoologist is justified in
denoting them '^ missing links,'^ because they seem to
have been intermediate between groups that have
diverged so widely during recent epochs as to render
their common ancestry scarcely credible.

With these general results in mind, we must now
become acquainted with such subjects as the interpre-
tation of fossils, the causes for the incompleteness of
the series, the conditions for fossilization, the forces of
geological nature, and other matters that make the
fossils themselves intelligible as scientific evidence.

Many views have been entertained regarding the
actual nature of the relics of antiquity exhumed from
the rocks or exposed upon the surface by the wear and
tear of natural agencies. In eariiest times such things
were variously considered as curious freaks of geo-
logical formation, as sports of nature, or as the remains
of the slain left upon the battle-ground of mythical
Titans. Some of the Greeks supposed that fossils

78 DOCTRINE OF EVOLUTION

were parts of animals formed in the bowels of the earth
by a process of spontaneous generation, which had died
before they could make their way to the surface. They
were sometimes described as the bones of creatures
stranded upon the dry land by tidal waves, or by some
such catastrophe as the traditional flood of the scrip-
tures. In medieval times, and even in our own day,
some people who have been opposed to the acceptance
of any portion of the doctrine of evolution have actually
defended the view that the things called fossils were
never the shells or bones of animals living in bygone
times, but that they onl}'' simulate such things and have
been created as such together with the layers of rock
from which they may have been taken. If we employed
the same arguments in dealing with the broken frag-
ments of vases and jewelry taken from the Egyptian
tombs or from the buried ruins of Pompeii, we would
have to believe that such pieces were created as frag-
ments and that they were never portions of complete
objects, just because no one alive to-day has ever seen
the perfect vessel or bracelet fashioned so long ago.
Common sense directs us to discard such a fantastic
interpretation in favor of the view that fossils are what
they seem to be — simply relics of creatures that lived
when the earth was younger.

Until this common sense view was adopted there was
no science of palaeontology. Cuvier was the first great
naturalist to devote particular attention to the mainly
unrelated and unverified facts that had been discovered
before his time. He was truly the originator of this
branch of zoology, for he brought together the observa-
tions of earlier men and extended his own studies widely

EVIDENCE OF FOSSIL REMAINS 79

and surely, emphasizing particularly the necessity for
noting carefully the geological situation of a fossil in
rocks of an older or later period of formation. His
great result was the demonstration that many groups
of animals existed in earlier ages that seem to have no
descendants of the same nature to-day, and also that
many or most of our modern groups are not represented
in the earliest formed sedimentary rocks, although these
recent forms possess hard parts which would surely be
present somewhere in these levels if the animals actually
existed in those times. But the meaning of these
facts escaped Cuvier's mind. He was a behever in
special creation, Hke Linnaeus and all but a few among
his predecessors, and he explained the diversity of
the faunas of different geological times in what seems
to us a very simple and naive way. In the beginning,
he held, when the world was created, it was furnished
with a complete set of animals and plants. Then some
great upheaval of nature occurred which overwhelmed
and destroyed all living creatures. The Creator then,
in Cuvier's view, proceeded to construct a new series of
animals and plants, which were not identical with those
of the former time, but were created according to the
same general working plans or architectural schemes
employed before. Another cataclysm was supposed
to have occurred, which destroyed the second series of
organisms and laid a new covering of rocks over the
earth's surface for a subsequent period of relative quiet ;
and so the process was continued. By this account,
Cuvier endeavored to reconcile the doctrine of super-
natural creation and intervention with the obvious
facts that organisms have differed at various times in

80 DOCTRINE OF EVOLUTION

the earth's history. Although he saw that animals of
successive periods displayed similar structures, like
the skeleton of vertebrates, which testified to some
connection, Cuvier could not bring himself to believe
that this connection was a genealogical one.

Mainly through the influence of the renowned Eng-
lish man of science, Charles Lyell, the students of the
earth came to the conclusion that its manifold struc-
tures had developed by a slow and orderly process that
was entirely natural ; for they found no evidence of any
sudden and drastic world-wide remodeling such as that
postulated by the Cuvierian hypothesis of catastrophe.
The battle waged for many years ; but now naturalists
beheve that the forces of nature, whose workings may
be seen on all sides at the present time, have recon-
structed the continents and ocean beds in the past in
the same way that they work to-day. The long name
of ^^uniformitarianism" is given to Ly ell's doctrine,
which has exerted an influence upon knowledge far
outside the department of geology. Darwin tells us
how much he himself was impressed by it, and how it
led him to study the factors at work upon organic
things to see if he could discern evidence of a biological
uniformitarianism, according to which the past history
of living things might be interpreted through an under-
standing of their present lives.

What, now, are the reasons why the palseontological
evidence is not complete and why it cannot be ? In the
first place the seeker after fossil remains finds about
three fifths of the earth's surface under water so that

EVIDENCE OF FOSSIL REMAINS 81

he cannot explore vast areas of the present ocean beds
which were formerly dry land and the homes of now
extinct animals. Thus the field of investigation is
seriously restricted at the outset, but the naturahst
finds his work still more limited, in so far as much of the
dry land itself is not accessible. The perennial snows
of the Arctic region render it impossible to make a
thorough search in the frigid zone, and there are many
portions of the temperate and torrid zones that are
equally unapproachable for other reasons. But even
where exploration is possible, the surface rocks are the
only ones from which remains can be readily obtained,
for the layers formed in earlier ages are buried so deeply
that their contents must remain forever unknown in
their entirety. Only a few scratches upon the earth's
hard crust have been made here and there, so it is small
wonder that the complete series of extinct organisms
has not been produced by the palaeontologist.

A brief survey of the varied groups of animals them-
selves is sufficient to bring to light many biological
reasons which account for still more of the vacant
spaces in the palaeontological record. We would hardly
expect to find remains of ancient microscopic animals
like the protozoa, unless they possessed shells or other
skeletal structures which in their aggregate might form
masses like the chalk beds of Europe. Jellyfish and
worms and naked mollusks are examples of the numerous
orders of lower animals having no hard parts to be
preserved, and so all or nearly all of the extinct species
belonging to these groups can never be known. But
when an animal like a clam dies its shell can resist the
disintegrating effects of bacteria and other organic

Q

82 DOCTRINE OF EVOLUTION

and inorganic agencies which destroy the soft parts,
and when a form Hke a lobster or a crab, possessing a
body protected by closely joined shell segments, falls
to the bottom of the sea, the chances are that much of
the animal's skeleton will be preserved. Thus it is
that corals, Crustacea, insects, mollusks, and a few other
kinds of lower forms constitute the greater mass of
invertebrate palseontological materials because of their
supporting structures of one kind or another. Perhaps
the skeletal remains of the vertebrates of the past
provide the student of fossils with his best facts, on
account of the resistant nature of the bones themselves,
and because the backboned animals are relatively mod-
ern ; then, too, the rocks in which their remains occur
have not been so much altered by geological agencies,
or buried so deeply under the strata formed later.
Of course only the hardest lands of shells would remain
as such after their burial in materials destined to turn
into rock ; in the majority of cases, an entombed bone
is infiltrated or replaced by various mineral substances
so that in time httle or nothing of the original thing
would remain, though a mold or a cast would persist.
But even if an animal of the past possessed hard
structures, it must have satisfied certain limited condi-
tions to have its remains prove serviceable to students
of to-day. A dead mammal must fall upon ground that
has just the right consistency to receive it ; if the soil is
too soft, its several parts will be separated and scattered
as readily as though it had fallen upon hard ground
where it would be torn to pieces by carnivorous ani-
mals. The dead body must then be covered up by a
blanket of silt or sand like that which would be depos-

EVIDENCE OF FOSSIL REMAINS 83

ited as the result of a freshet. If a skeleton is too
greatly broken up or scattered, it may be difficult or
even impossible for its discoverer to piece together the
various fragments and assemble them in their original
relations. Very few individuals have been so buried
and preserved as to meet the conditions for the forma-
tion of an ideal fossil. To realize how little may be left
of even the most abundant of higher organisms, we have
only to recall that less than a century ago immense
herds of bison and wild horses roamed the Western
plains, but very few of their skulls or other bones re-
main to be enclosed and fossilized in future strata of
rocks. When we appreciate all these difficulties, both
geological and biological, we begin to see clearly why
the ancient lines of descent cannot be known as we
know the path and mode of embryonic transformation.
The wonder is not that the palseontological record is ,
incomplete, but that there is any coherent and decipher- j
able record at all. Yet in view of the many and varied *
obstacles that must be surmounted by the investigator,
and the adverse factors which reduce the available
evidence, the rapidly growing body of palaeontological
facts is amply sufficient for the naturalist to use in for-
mulating definite and conclusive principles of evolution.

For the purposes of palaeontology, the most essential
data of geology are those which indicate the relative
ages of the strata that make up the hard outer crust of
the earth, for only through them can the order of animal
succession be ascertained. It does not matter exactly
how old the earth may be. While it is possible to

.(

84 DOCTRINE OF EVOLUTION

determine the approximate length of time required for
the construction of sedimentary rocks Uke those which
natural agencies are producing to-day, there are few
definite facts to guide speculation as to the mode or
duration of the process by which the first hard crys-
talline surface of the earth was formed. But palaeon-
tology does not care so much about the earliest
geological happenings, for it is concerned with the
manifold animal forms that arose and evolved after life
appeared on the globe. Questions as to the way life
arose, and as to the earliest transformations of the
materials by which the earth was first formed are not
within the scope of organic evolution, although they
relate to intensely interesting problems for the student
of the process of cosmic evolution.

According to the account now generally accepted, the
original material of the earth seems to have been a
semi-solid or semi-fluid mass formed by the condensation
of the still more fluid or even gaseous nebula out of
which all the planets of the solar system have been
formed and of which the sun is the still fiery core. As
soon as the earth had cooled sufficiently its substances
crystallized and wrinkled to form the first mountains
and ridges ; between and among these were the basins
which soon filled with the condensing waters to become
the earliest lakes and oceans. The wear and tear of
rains and snows and winds so worked upon the surfaces
of the higher regions that sediments of a finer or coarser
character like sand and mud and gravel were washed
down into the lower levels. These sediments were
afterwards converted into the first rocks of the so-called
stratified or sedimentary series, as contrasted with the

EVIDENCE OF FOSSIL REMAINS 85

crystalline or plutonic rocks like the original mass of
the earth and the kinds forced to the surface by vol-
canic eruptions. Later the earth wrinkled again in
various ways and places so that new ridges and moun-
tains were formed with new systems of lakes and oceans
and rivers ; and again the elements continued to erode
and partially destroy the higher masses and to lay down
new and later series of sedimentary rocks upon the old.
It seems scarcely credible that the apparently weak
forces of nature like those we have mentioned are suffi-
ciently powerful to work over the massive crust of the
earth as geology says they have. Our attention is
caught, as a rule, only by the greater things, like the
earthquakes at San Francisco and Valparaiso, and the
tidal waves and cyclones of the South Seas ; but the re-
sults of these sporadic and local cataclysms are far less
than the effects of the persistent everyday forces of
erosion, each one of which seems so small and futile.
When we look at the Rocky Mountains with their high
and rugged peaks, it seems almost impossible that rain
and frost and snow could ever break them up and wear
them down so that they would become like the rounded
hills of the Appalachian Mountain chain, yet this is
what will happen unless nature's ways suddenly change
to something which they are not now. A visitor to the
Grand Canon of the Colorado sees a magnificent chasm
over a mile in depth and two hundred miles long which
has actually been carved through layer after layer of
solid rock by the rushing torrents of the river. Per-
haps it is easier to estimate the geological effects of a
river in such a case as Niagara. Here we find a deep
gorge below the famous falls, which runs for twenty

86 DOCTRINE OF EVOLUTION

miles or so to open out into Lake Ontario. The water
passing over the brim of the falls wears away the edge
at a rate which varies somewhat according to the harder
or softer consistency of the rocks, but which, since
1843, has averaged about 104 inches a year. Knowing
this rate, the length of the gorge, and the character of
the rocky walls already carved out, the length of time
necessary for its production can be safely estimated. It
is about 30,000 to 40,000 years, not a long period when
the whole history of the earth is taken into account. A
similar length of time is indicated for the recession of the
Falls of St. Anthony, of the Mississippi River, an agree-
ment that is of much interest, for it proves that the two
rivers began to make their respective cuttings when the
great ice-sheet receded to the north at the end of the
Glacial epoch.

What has become of the masses washed away during
the formation of these gorges ? As gravel and mud and
silt the detritus has been carried to the still waters of
the lower levels, to be laid down and later solidified into
sandstone and slate and shale. All over the continents
these things are going on, and indefatigable forces are
at work that slowly but surely shear from the surface
almost immeasurable quantities of earth and rock to be
transported far away. In some instances it is possible
to find out just how much effect is produced in a given
period of time, especially in the case of the great river
systems. For example, the mass of the fine particles of
mud and silt carried in a given quantity of the water of
the Mississippi as it passes New Orleans can be accu-
rately measured, and a satisfactory determination can
also be made of the total amount of water carried by in a

EVIDENCE OF FOSSIL REMAINS 87

year. From these figures the amount of materials in
suspension discharged into the Gulf of Mexico becomes
known. It is sufficient to cover one square mile to the
depth of 269 feet ; in twenty years it is one cubic mile,
or five cubic miles in a century. Turning now to the
other aspect of this process, and the antecedent causes
which produce these effects, it appears that the area of
the Mississippi River basin is 1,147,000 square miles —
about one third of the total area of the United States.
Knowing this, and the annual waste from its surface, it
is easy to demonstrate that it will take 6000 years to
plane off an average of one foot of soil and rock from
the whole of this immense area. Of course only an
inch or a few inches will be taken from some regions
where the ground is harder or rockier, or where little
rain falls, while many feet will be washed away from
other places. The waters of the Hoang-ho come from
about 700,000 square miles of country, from which one
foot of soil is washed away in 1464 years. The Ganges
River, draining about 143,000 square miles, carries off
a similar depth of eroded materials from its basin in
823 years ! Should we add to the above figures those
that specify the bulk of the chemical substances in
solution carried by these waters, the total would be
even greater. We know that in the case of the Thames
River, calcareous substances to the amount of 10,000
tons a year are carried past London, and all this mineral
has been dissolved by rain-water from the chalky cliffs
and uplands of England, so that the land has become
less by this amount. Thus we learn that vast altera-
tions are being made in the structure of great continents
by rain and rivers, as well as by glaciers and other

88 DOCTRINE OF EVOLUTION

geological agencies. And at the same time that old
strata are undergoing destruction new ones are in
process of construction at other places, where animal
remains can be embedded and preserved as fossils. The
forces at work seem weak, but they continue their opera-
tions through ages that are beyond our comprehension
and they accomplish results of world-building magnitude.
Thus the whole process of geological construction is
such that older exposed strata continually undergo
disintegration, but this involves the destruction of any
fossils that they might contain. The very forces that
preserve the relics of extinct animals at one time undo
their work at a later period. There are many other
influences besides that destroy the regularity of rock
layers or change their mineralogical characters by meta-
morphosis. It is easier to see how volcanic outbursts
alter their neighboring territory. The intense sub-
terranean heat and imprisoned steam melt the deeper
substances of the earth's crust, so that these materials
boil out, as it were, where the pressure is greatest, and
where lines of fracture and lesser resistance can be found.
Because so much detritus is annually added to the
ocean floors — enough to raise the levels of the oceans
by inches in a century — it is natural that greater
pressures should be exerted in these areas than in the
slowly thinning continental regions. These are some
of the reasons why volcanoes arise almost invariably
along the shores or from the floors of great ocean beds.
The chain that extends from Alaska to Chili within the
eastern shore of the Pacific Ocean, and the many hun-
dreds of volcanoes of the Pacific Islands bring to the
surfac'e vast quantities of eruptive rocks which break

EVIDENCE OF FOSSIL REMAINS 89

up and overlie the sedimentary strata formed regularly
in other ways and at other times. The volcanoes of the
Java region alone have thrown out at least 100 cubic
miles of lava, cinders, and ashes during the last 100 years
— twenty times the bulk of the materials discharged
into the Gulf of Mexico by the Mississippi River in the
same period of time.

From these and similar facts, the naturalist finds how
agencies of the present construct new rocks and alter
the old ; and so in the light of this knowledge, he pro-
ceeds with his task of analyzing the remote past, confi-
dent that the same natural forces have done the work of
constructing the lower geological levels because these
earlier products are similar to those being formed to-day.
After learning this much, he must immediately under-
take to arrange the strata according to their ages. This
might seem a difficult or even an impossible task, but
the rocks themselves provide him with sure guidance.

Wherever a river has graven its deep way through an
area of hard rocks, as in the case of Niagara, the walls
display on their cut surfaces a series of lines and planes
showing that they are superimposed layers formed
serially by deposits that have differed some or much at
different times according to the circumstances control-
ling the erosion of their constituent particles. A layer
of several feet in thickness may be composed of com-
pact shale, while above it will be a zone of limestone,
and again above this another layer of shale. Successive
strata like these, where they are parallel and obviously
undisturbed, are evidently arranged in the order of their

90 DOCTRINE OF EVOLUTION

formation and age. But by far the most impressive
demonstration of the basic principle of geology em-
ployed for the determination of the relative ages of
rocks is the mighty Canon of the Colorado. As the
traveler stands on the winding rim of this vast chasm,
his eye ranges across 13 miles of space to the opposite
walls, which stretch for scores of miles to the right and
left ; upon this serried face he will see zone after zone
of yellow and red and gray rock arranged with mathe-
matical precision and level in the same order as on the
steep slopes beneath him. Plain common sense tells
him that the great sheets of rock stretched continuously
at one time between the now separate walls, and that
the various strata of sandstone and limestone were
deposited in successive ages from below upwards in the
order of their exposure. When now he extends his
explorations to another state like Utah or Wyoming, he
may find some but not all of the series exhibited in the
Grand Caiion, overlaid or underlaid by other strata
which in their turn can be assigned to definite places in
the sequence. By the same method, the geologist
correlates and arranges the rocks not only of different
parts of the same state, or of neighboring states, but
even those of widely separated parts of North America
and of different continents. But he learns that he must
refrain from over-hasty conclusions, for he soon finds
that the sedimentary rocks have not been constructed
at the same rate in different places during one and the
same epoch, and that rocks formed even at one period
are not always identical in nature. But his guiding prin-
ciple is sensible and reasonable, and by employing it with
due caution he provides the palaeontologist with the req-

EVIDENCE OF FOSSIL REMAINS

91

uisite knowledge for his special task, which is to arrange
the extinct animals whose remains are found as fossils of
various earth ages in the order of their succession in time.

Condensed Table of Pal^ontological Facts

Years

Necessary for

Formation

Number of

Feet in
Thickness

Geological
Age

Geological
Epoch

Order of
Appearance op
Characteristic

Groups

Recent

or

Quaternary

Mammals

Birds

Reptiles

Amphibia

Fishes

Inverte-
brates

5,000,000

25,000

Cenozoic

or
Tertiary

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

—

—

—

4,000,000

23,000

Mesozoic

or
Secondary

Cretaceous

Jurassic

Triassic

21,000,000

106,000

Palaeozoic

or

Primary

Permian

Carboniferous

Devonian

Silurian

Cambrian

20,000,000

30,000

Azoic ]

Archaean

After what seems an unduly long preparation, we
now come to the actual biological evidence of evolution
provided by the results of this division of zoological
science. But all of the foregoing is fundamentally part
of this department of knowledge and it is absolutely
essential for any one who desires to understand what
the fossils themselves demonstrate.

92 DOCTRINE OF EVOLUTION

The oldest sedimentary rocks are devoid of fossil
remains and so they are called the Azoic or Archsean.
They comprise about 30,000 feet of strata which seem to
have required at least 20,000,000 years for their forma-
tion. This period is roughly two-fifths of the whole
time necessary for the formation of all the sedimentary
rocks, and this proportion holds true even if the entire
period of years should be taken as 100,000,000 instead
of 50,000,000 or less. The earth during this early age
was slowly organizing in chemical and physical respects
so that living matter could be and indeed was formed
out of antecedent substances — but this process does
not concern us here. The important fact is that the
second major period, called the Palseozoic, or ^^age of
ancient animals," saw the evolution of the lowest
members of the series, — the invertebrates, — and the
most primitive of the backboned animals, like fishes and
amphibia. The rocks of this long age include about
106,000 feet of strata, demanding some 21,000,000 or
22,000,000 years for their deposition. Thus it is proved
that the invertebrate animals were succeeded in time by
the higher vertebrates, which is exactly what the evi-
dences of the previous categories have shown. When
we remember that the lower animals are devoid as a rule
of skeletal structures that might be fossilized, and when
we recall the fact that the strata of the palaeozoic pro-
vided the materials out of which the upper layers were
formed afterwards, we can understand why the ancient
members of the invertebrate groups are not known as
well as the later and higher forms like vertebrates. Yet
all the fossils of these relatively unfamiliar creatures
clearly prove that no complex animal appears upon a

EVIDENCE OF FOSSIL REMAINS 93

geological horizon until after some simple type belong-
ing to a class from which it may have taken its origin ;
in brief, there are no anachronisms in the record, which
always corresponds with the record written by com-
parative anatomy, wherever the facts enable a compar-
ison to be made.

But the extinct animals of the third and fourth ages
are more interesting to us, because there are more of
them and because they are more like the well-known
organisms of our present era. These two ages are
called the Mesozoic or Secondary, and the Cenozoic or
Tertiary. The former is so named because it was a
transitional age of animals that are intermediate in a
general way between the primitive forms of the pre-
ceding age and those of the next period; the latter
name means the '^ recent-animal" age, when evolution
produced not only the larger groups of our present
animal series, but also many of the smaller branches of
the genealogical tree like orders and families to which
the species of to-day belong.

Confining our attention to the large vertebrate classes,
the testimony of the rocks proves, as we have said, that
fishes appeared first in what are called the Silurian and
Devonian epochs, where they developed into a rich
and varied array of types unequaled in modern times.
At that period, they were the highest existing animals —
the ^^ lords of creation," as it were. To change the
figure, their branch constituted the top of the animal
tree of the time, but as other branches grew upwards
to bear their twigs and leaves, as the counterparts of
species, the species of the branch of fishes decreased in
number and variety, as do the leaves of a lower part of a
tree when higher hmbs grow to overshadow them.

94 DOCTRINE OF EVOLUTION

Following the fishes, the amphibia arose during the
coal age or Carboniferous, usurping the proud position
of the lower vertebrate class. The reptiles then ap-
peared and gained ascendancy over the amphibia, to
become in the Mesozoic age the highest and most varied
of the existing vertebrates. At that time there were
the great land dinosaurs with a length of 80 feet, like
Brontosaurus ; aquatic forms like Ichthyosaurus and
Plesiosaurus, whose mode of evolution from terrestrial
to swimming habits was like that of seals and penguins
of far later eras. Flying reptiles also evolved, to set an
example for the bats of the mammalian class, for both
kinds of flying organisms converted their anterior
limbs into wings, although in different ways.

During the Triassic and Jurassic periods of the Meso-
zoic age, the first birds and mammals appeared to follow
out their diverging and independent lines of descent.
Palaeontology makes it possible to trace the origin and
development of many of the different branches that
grew out of the mammalian limb from different places
and at different times during the Mesozoic and the
following age, called the Cenozoic, or age of recent ani-
mals. It is unnecessary, however, for us to review more
of the details : the main result is obvious ; namely,
that the appearance of the great classes of vertebrates
is in the order of comparative anatomy and embryology.
V Not only, then, is the fact of evolution rendered trebly
I sure, but the general order of events is thrice and in-
j dependently demonstrated to be one and the same,
s Surely we must see that no reasonable explanation
l other than evolution can be given for these basic facts
and principles

EVIDENCE OF FOSSIL REMAINS 95

Turning now to the second division of palseontological
evidence, we come to those groups where abundant
materials make it possible to arrange the animals of
successive epochs in series that may be remarkably
complete. For the reasons specified, the backboned
animals provide the richest arrays of these series, and
such histories as those of horses and elephants have
taken their places in zoological science as classics.
But even among the invertebrates significant cases
may be found. For example, in one restricted locality
in Germany the shells of snails belonging to the genus
Paludina have been found in superimposed strata in the
order of their geological sequence. The ample material
shows how the several species altered from age to age
by the addition of knobs and ridges to the surface of the
shell, until the fossils in the latest rocks are far different
from their ancestors in the lowermost levels. Yet the
intervening shells fill in the gaps in such a way as to
show almost perfectly how the animals worked out
their evolutionary history. This example illustrates
the nature of many other known series of mollusks and
of brachiopods, extending over longer intervals and
connecting more widely separated ages like the Second-
ary and the present period.

Since the doctrine of evolution and its evidences
began to occupy the thoughts of the intellectual world
at large, no fossil forms have received more attention
than the ancient members of the horse tribe. As we
have learned, a modern horse is described by com-
parative anatomy as a one-toed descendant of remote
five-toed ancestors. When the hoofed animals of
modern times were reviewed as subjects for compara-

96 DOCTRINE OF EVOLUTION

tive anatomical study, the odd-toed forms arranged
themselves in a series beginning with an animal like an
elephant with the full number of five digits on each
foot and ending at the opposite extreme with the horse.
A reasonable interpretation of these facts was that
the animals with fewer toes had evolved from ancestors
with five digits, of which the outer ones had progres-
sively disappeared during successive geological periods,
while the middle one enlarged correspondingly. The
facts provided by palaeontology sustain this contention
with absolutely independent testimony. Disregarding
some problematical five-toed forms like Plienacodus, the
first type of undoubted relationship to modern horses
is Hyracotherium, a little animal about three feet long
that lived during the Eocene period of the Cenozoic
epoch. Its forefeet had four toes each, and its hinder
limbs ended with three toes armed with small hoofs,
but one of its relatives of the same time has a vestige
of another digit on the hind foot. By the geological
time mentioned, therefore, the earliest true horses had
already lost some of the toes that their progenitors
possessed. In the Miocene the extinct species, ob-
viously descended from the Eocene forms, had lost
more of their toes; still higher, that is, in the rocks
formed during succeeding periods of time, the animals of
this division are much larger and each of their feet has
only three toes, of which the middle one is the largest
while the ones on the sides are small and withdrawn
from the ground so as to appear as useless vestiges.
To produce modern horses and zebras from these
nearer ancestors, few additional changes in the structure
of the feet are necessary, for the lateral toes need only

EVIDENCE OF FOSSIL REMAINS 97

to become a little more reduced and the middle one to
enlarge slightly to give the one-toed hmb of modern
types, with its sphnt-like vestiges still in evidence to
show that the ancestor's foot comprised more of
these terminal elements. Comparing the animals of
successive periods, these and other skeletal structures
demonstrate that the ancestry of each group of species
is to be found in the animals of the preceding epoch,
and that the whole history of horses is one of natural
transformation, — in a word, of evolution.

No less interesting in their own way are the remains
of other hoofed forms that lead down to the elephants
of to-day and to the mammoth and mastodon of rela-
tively recent geologic times. Common sense would
lead to the conclusion that a form like a modern tapir
was the prototype from which these creatures have
arisen, and common sense would lead us to expect that
if any fossils of the ancestors of the modern group
of elephants occurred at all they would be like tapirs.
Thus a fossil of much significance in this connection is
Moeriiherium, whose remains have been found in the
rocks exposed in the Libyan desert, for this creature
was practically a tapir, while at the same time its
characters of muzzle and tusk mark it as very close
to the ancestors of the larger woolly elephants of later
geological times, when the trunk had grown consider-
ably and the tusks had become greatly prolonged.
Again the fossil sequence confirms the conclusions
of comparative anatomy, regarding the mode by which
certain modern animals have evolved.

The fossil deer of North America, as well as many
other even-toed members of the group of mammalia

98 DOCTRINE OF EVOLUTION

possessing hoofs, provide the same kind af conclusive
evidence. The feature of particular interest in the
case of their horns, is a correspondence between the
fossil sequence and the order of events in the life-history
of existing species, — that is, between the results of
palaeontology and of embryology. Horns of the
earliest known fossil deer have only two prongs; in
the rocks above are remains of deer with additional
prongs, and point after point is added as the ancient
history of deer is traced upwards through the rocks to
modern species. We know that the life-history of
a modern species of animals reviews the ancestral
record of the species, and what happens during the
development of deer can be directly compared with
the fossil series. It is a matter of common knowledge
that the year-old stag has simple spikes as horns, and
that these are shed to be replaced the following year
by larger forked horns. Every year the horns are lost
and new ones grow out, and become more and more
elaborately branched as time goes on, thus giving a
series of developmental stages that faithfully repeats
the general order of fossil horns. Even Agassiz,who
was a believer in special creation and an opponent
of evolution, was constrained to point out many other
instances, mainly among the invertebrata, where there
was a like correspondence between the ontogeny of
existing species and their phylogenetic history as
revealed by the fossil remains of their ancestors.

In the last place, we must give more than a passing
consideration to some of the extinct types of animals

EVIDENCE OF FOSSIL REMAINS 99

that occupy the position of ^4inks" between groups
now widely separated by their divergence in evolution
from the same ancestors. Perhaps the most famous
example is Archceopteryx found in a series of slates
in Germany. This animal is at once a feathered,
flying reptile, and a primitive bird with countless
reptilian structures. Its short head possesses lizard-
like jaws, all of which bear teeth ; its wings comprise five
clawed digits ; its tail is composed of a long series of
joints or vertebrae, bearing large feathers in pairs ;
its breastbone is flat and like a plate, thus resembling
that of reptiles and differing markedly from the
great keeled breastbone of modern flying birds, whose
large muscles have necessitated the development
of the keel for purposes of firm attachment. In
brief, this animal was close to the point where
reptiles and birds parted company in evolution, and
although it was a primitive bird, it is in a true sense a
^'missing hnk" between reptiles and the group of
modern birds. Other fossil forms like Hesperornis
and Ichthyornis, whose remains occur in the strata of a
later date, fill in the gap between Archceopteryx and
the birds at the present time, for among other things
they possess teeth which indicate their origin from
forms like Archceopteryx, while in other respects they
are far nearer the birds of later epochs. That these
links are not unique is proved by numerous other
examples known to science, such as those which connect
amphibia and reptiles, ancient reptiles and primitive
mammals, as well as those which come between the
different orders of certain vertebrate classes.

In summarizing the foregoing facts, and the larger

100 DOCTRINE OF EVOLUTION

bodies of evidence that they exempUfy, we learn how
surely the testimony of the rocks estabhshes evolution
in its own way, how it confirms the law of recapitulation
demonstrated by comparative embryology, and how
it proves that the greater and smaller divisions of
animals have followed the identical order in their
evolution that the comparative study of the present
day animals has independently described.

The facts of geographical distribution constitute
the fifth division of zoology, and an independent
class of evidences proving the occurrence of evolution.
This department of zoology assumed its rightful status
only after the other divisions had attained considerable
growth. Many naturalists before Darwin and Wallace
and Wagner had noticed that animals and plants
were by no means evenly distributed over the surface
of the globe, but until the doctrine of evolution cleared
their vision they did not see the meaning of these facts.
As in the case of all the other departments of zoology
the immediate data themselves are familiar, but because
they are so obvious the mind does not look for their
interpretation but accepts the facts at their face value.
While the phenomena of distribution are no less fascinat-
ing to the naturalist, and no less effective in their dem-
onstration of evolution, their comprehensive treatment
would demand more space than the whole purpose of the
present description of organic evolution would justify.
Thus a brief outline only can be given of the salient
principles of this subject in order that their bearing
upon the problem of species may be indicated.

EVIDENCE OF FOSSIL REMAINS 101

Even as children we learn many facts of animal
distribution; every one knows that lions occur in
Africa and not in America, that tigers live in Asia
and Malaysia, that the jaguar is an inhabitant of the
Brazilian forests, and that the American puma or
mountain hon spreads from north to south and from
east to west throughout the American continents.
The occurrence of differing human races in widely
separated localities is no less familiar and striking,
for the red man in America, the Zulu in Africa, the
Mongol and Malay in their own territories, display
the same discontinuity in distribution that is character-
istic of all other groups of animals and of plants as
well. As our sphere of knowledge increases, we are
impressed more and more forcibly by the diversity
and unequal extent of the ranges occupied by the
members of every one of the varied divisions of the
organic world. Another fact which becomes sig-
nificant only when science calls our attention to it
is the absence from a land like Australia of higher
mammals such as the rabbit of Europe. The hy-
pothesis of special creation cannot explain this absence
on the assumption that the rabbit is unsuited to the
conditions obtaining in the country named, for when
the species was introduced into Australia by man,
it developed and spread with marvelous rapidity and
destructive effect. It may seem impossible that facts
like these could possess an evolutionary significance,
but they are actual examples of the great mass of data
brought together by the naturalists who have seen in
them something to be interpreted, and who have sought
and found an explanation in the formularies of science.

102 DOCTRINE OF EVOLUTION

The general principles of distribution appear with
greatest clearness when an examination is made of
the animals and plants of isolated regions like islands.
The Galapagos Islands constitute a group that has
figured largely in the Hterature of the subject, partly
because Darwin himself was so impressed by what he
found there in the course of his famous voyage around the
world in the ^'Beagle.'' They form a cluster on the
Equator about six hundred miles west of the nearest
point of the neighboring coast of South America.
Although the lizards and birds that live in the group
differ somewhat among themselves as one passes from
island to island, on the whole they are most like the
species of the corresponding classes inhabiting South
America. Why should this be so ? On the hypothesis
of special creation there is no reason why they should
not be more like the species of Africa or Australia than
like those of the nearest body of the mainland. The
explanation given by evolution is clear, simple, and
reasonable. It is that the characteristic island forms
are the descendants of immigrants which in greatest
probability would be wanderers from the neighboring
continent and not from far distant lands. Reaching
the isolated area in question the natural factors of
evolution would lead their offspring of later generations
to vary from the original parental types, and so the
peculiar Galapagos species would come into being.
The fact that the organisms living on the various
islands of this group differ somewhat in lesser details
adds further justification for the evolutionary inter-
pretation, because it is not probable that all the isl-
ands would be populated at the same time by similar

EVIDENCE OF FOSSIL REMAINS 103

stragglers from the mainland. The first settlers in
one place would send out colonies to others, where
independent evolution would result in the appearance
of minor differences pecuHar to the single island.
In this manner science interprets the general agree-
ment between the animals of the Azores Islands and
the fauna of the northwestern part of Africa, the
nearest body of land, from which it would be most
natural for the ancestors of the island fauna to come.
The land-snails inhabiting the various groups of
islands scattered throughout the vast extent of the
Pacific Ocean provide the richest and most ideal material .
for the demonstration of the principles of geographical /
distribution. In the Hawaiian Islands snails of the'
family of AchatinelUdse occur in great abundance,
and hke the hzards of the Galapagos Islands different
species occur on the different members of the group.
Within the confines of one and the same island, they
vary from valley to valley, and the correlation between
their isolation in geographical respects and specific dif-
ferences on the other hand, first pointed out by Gulick,
makes this tribe of animals classical material. In
Polynesia and Melanesia are found close relatives of
the Achatinelhdse, namely, the Partulse, which are
thus in relative proximity to the Achatinellidae and
not on the other side of the world. Furthermore,
the Partulse are not alike in all of the groups of Polynesia
where they occur; the species of the Society Islands
are absolutely distinct from those of the Marquesas,
Tonga, Samoan, and Solomon Islands, although they
agree closely in the basic characters that justify their
reference to a single genus. The geological evidence

104 DOCTRINE OF EVOLUTION

tells us that these islands were once the peaks of moun-
tain ranges rising from a Pacific continent which has
since subsided to such an extent that the mountain
tops have become separate islands. Thus the resem-
blances between Hawaiian and Polynesian snails, and
the closer similarities exhibited by the species of the
various groups of Polynesia, are intelligible as the marks
of a common ancestry in a widespread continental
stock, while the observed differences show the extent
of subsequent evolution along independent lines followed
out after the isolation of the now separated islands.
The principle may be worked out in even greater
detail, for ii appears that within the Umits of one group
diverse forms occupy different islands, evolved in
different ways in their own neighborhoods; while
in one and the same island, the populations of the
different valleys show marked effects of divergence in
later evolution, precisely as in the case of the classic
Achatinellidae of the Hawaiian Islands.

The broad and consistent principle underlying these
and related facts is this : there is a general cor-
respondence between the differences displayed by the
organisms of two regions and the degree of isolation or
proximity of these two areas. Thus the disconnected
but neighboring areas of the Galapagos Islands and
South America support species that resemble each
other closely, for the reasons given before; long iso-
lated areas like Australia and its surroundings possess
peculiar creatures like the egg-laying mammals, and
all of the pouched animals or marsupials with only
one or two exceptions like our own x4merican opos-
sum, — a correlation between a geological and geo-

EVIDENCE OF FOSSIL REMAINS 105

graphical discontinuity on the one hand and a faunal
peculiarity on the other that reinforces our confidence
in the evolutionary interpretation of the facts of distri-
bution.

It is true that the various classes of animals do not
always appear with coextensive ranges. The barriers
between two groups of related species will not be the
same in all cases. A range like the Rocky Mountains
will keep fresh-water fish apart, while birds and mam-
mals can get across somewhere at some time. All
these things must be taken into account in analyzing
the phenomena of distribution, and many factors must
be given due attention ; but in all cases the" reasons for
the particular state of affairs in geographical and
biological respects possess an evolutionary significance.

Having then all the facts of animal natural history
at his disposal, and the uniform principles in each
body of fact that demonstrate evolution, it is small
wonder that the evolutionist seems to dogmatize when
he asserts that descent with adaptive and divergent
modification is true for all species of living things.
The case is complete as it stands to-day, while it is
even more significant that every new discovery falls
into line with what is already known, and takes its
natural place in the all-inclusive doctrine of organic
evolution. Because this explanation of the characteris-
tics of the living world is more reasonable than any
other, science teaches that it is true.

IV

EVOLUTION AS A NATUKAL PROCESS

The purpose of the discussions up to this point has
been to present the reasons drawn from the principal
classes of zoological facts for beheving that Hving
things have transformed naturally to become what they
now are. Even if it were possible to make an ex-
haustive analysis of all of the known phenomena of
animal structure, development, and fossil succession,
the complete bodies of knowledge could not make the
evolutionary explanation more real and evident than
it is shown to be by the simple facts and principles
selected to constitute the foregoing outline. We have
dealt solely with the evidences as to the fact of evolu-
tion; and now, having assured ourselves that it is
worth while to so do, we may turn to the intelhgible
and reasonable evidence found by science which proves
that the familiar and everyday ''forces" of nature are
competent to bring about evolution if they have
operated in the past as they do to-day. Investigation
has brought to hght many of the subsidiary elements
. of the whole process, and these are so real and obvious
that they are simply taken for granted without a
suspicion on our part of their power until science
directs our attention to them.

For one reason or another, those who take up this

106

EVOLUTION AS A NATURAL PROCESS 107

subject for the first time find it difficult to banish
from their minds the idea that evolution, even if it ever
took place, has been ended. They think it futile to
expect that a scrutiny of to-day's order can possibly
find influences powerful enough to have any share in
the marvelous process of past evolution demonstrated
by science. The naturalists of a century ago held a
similar opinion regarding the earth, viewing it as an
immutable and unchanged product of supernatural
creation, until Lyell led them to see that the world is
a plastic mass slowly altering in countless ways. It
is no more true that living things have ceased to evolve
than that mountains and rivers and glaciers are fixed
in their final forms ; they may seem everlasting and
permanent only because a human life is so brief in
comparison with their full histories. Like the develop-
ment of a continent as science describes it, the origin
of a new species by evolution, its rise, culmination,
and final extinction may demand thousands of years ;
so that an onlooker who is himself only a conscious
atom of the turbulent stream of evolving organic life
does not live long enough to observe more than a small
fraction of the whole process. Therefore living species
seem unchanged and unchangeable until a conviction
that evolution is true, and a knowledge of the method
of science by which this conviction is borne upon one,
guide the student onwards in the further search for
the efl!icient causes of the process.

The biologist employs the identical methods used
by the geologist in working out the past history of
the earth's crust. The latter observes the forces at
work to-day, and compares the new layers of rock

108 DOCTRINE OF EVOLUTION

now being formed with the strata of deeper levels;
these are so much alike that he is led to regard the
constructive influences of the past as identical with
those he can now watch at work. Similarly the biologist
must first learn, as we have done, the principles of
animal construction and development, and of other
classes of zoological facts, and then he must turn his
attention from the dead object of laboratory analysis
to the workings of organic machines. The way an
organism lives its life in dynamic relations to the
varied conditions of existence, as well as the mutual
physiological relations of the manifold parts of a single
organism, reveal certain definite natural forces at work.
Therefore his next task is to compare the results ac-
complished by these factors in the brief time they may
be seen in operation with the products of the whole pro-
cess of organic evolution, to learn, like the geologist in
his sphere, that the present-day natural forces are able
to do what reason says they have done in the past.
When the subject of inquiry was the reality of
evolution, it was perhaps surprising to find that even
the most familiar animals like cats and frogs provided
adequate data for science to use in formulating its
principles. So it is with the matter of method; it
is unnecessary to go beyond the observations of a day
or a week of human life to find forces at work, as real
and vital as animal existence and organic fife them-
selves. This is true, because evolution is true, and be-
cause the lives of all creatures follow one consistent law.
Our task is therefore much more simple than mosf"
people suppose it to be; let us look about us and
classify what we may observe, increasing our knowl-

EVOLUTION AS A NATURAL PROCESS 109

edge from the wide array of equally natural facts
supplied by the biologist.

The analogies of the steamship and the locomotive
proved useful at many times during the discussion
of the fact of evolution, and even in the present con-
nection they will still be of service. The evolution
of these dead machines has been brought about by
man, who, as an element of their environment, has
been their creator as well as the director of their his-
torical transformations. The result of their changes
has been greater efficiency and better adjustment
or adaptation to certain requirements fixed by man
himself. The whole process of improvement has been
one, in brief, of trial and error; new inventions have
often been worthless, and they have been relegated to
the scrap-heap, while the better part has been finally
incorporated in the type machine. In brief, then,
the important elements in the evolution of these
examples have been three; first, adaptation, second, ;
the origination of new parts, and third, the retention \
of the better invention. '

Are the creatures of the living world so constituted
that biological equivalents of these three essential
elements of mechanical evolution can be found ? Are
organisms adapted to the circumstances controlling
their lives, and are they capable of changing naturally
from generation to generation, and of transmitting
their qualities to their offspring? These are definite
questions that bring us face to face with the funda-
mental problems relating to the dynamics or workings
of evolution. We need not ask for or expect to find
complete answers, for we know that it is impossible

no DOCTRINE OF EVOLUTION

to obtain them. But we may expect to accomplish
our immediate object, which is to see that evolution
is natural. Our attention must be concentrated upon
the three biological subjects of adaptation, variation ^
and inheritance, and we must learn why science describes
them as real organic phenomena and the results of
natural causes.

At the very outset, when the general characteristics
of living things were considered, much was said on
the subject of adaptation as a universal phenomenon
of nature. It was not contended that perfection is
attained by any living mechanism, but it was held that
no place exists in nature for an organism that is in-
capable of adjusting itself to the manifold conditions
of life. A modus vivendi must be established and some
satisfactory degree of adaptation must be attained,
or else an animal or a species must perish. With
this fundamental point as a basis, we look to nature
for two kinds of natural processes or factors, first,
those which may originate variations as primary
factors, — the counterparts of human ingenuity and
invention in the case of locomotive evolution, — and
the secondary factors of a preservative nature which
will perpetuate the more adaptive organic changes
produced by the first influences; it is clear that the
latter are no less essential for evolution than the first
causes for the appearance of variations.

The term '^variation" is employed for the natural
phenomenon of being or becoming different. It is an
obvious fact that no child is ever exactly like either

EVOLUTION AS A NATURAL PROCESS 111

of its parents or like any one of its earlier ancestors;
while furthermore in no case does an individual re-
semble perfectly another of its own generation or
family. This departure from the parental condition,
and the lack of agreement with others even of its
closest blood-relatives, are two familiar forms of
variation. As a rule, the degree to which a given
organism is said to vary in a given character is most
conveniently measured by the difference between its
actual condition and the general average of its species,
even though there is no such thing as a specimen of
average nature in all of its qualities. In brief, then,
variation means the existence of some differences
between an individual and its parents, its fraternity,
and, in a wider sense, all others of its species.

Passing now to the causes of variation, all of the
countless deviations of living things can be referred
to three kinds of primary factors ; namely, the environ-
mental, functional, and congenital influences that work
upon the organism in different ways and at different
times during its life. We shall learn that the evolu-
tionary values of these three classes are by no means
equal, but we take a long step forward when we reahze
that among the things we see every day are facts
demonstrating the reality of three kinds of natural
powers quite able to change the characters of organic
mechanisms. '

The ''environment" of an organism is everything
outside the creature itself. In the case of an animal
it therefore includes other members of its own kind,
and other organisms which prey upon its species or
which serve it as food, as well as the whole series of

112 DOCTRINE OF EVOLUTION

inorganic influences which first come to mind when the
term is used. For example, the environment of a Hon
includes other lions which are either members of its
own family, or else, if they live in the same region,
they are its more or less active rivals and competitors.
In the next place, other kinds of animals exist whose
lives are intimately related to the lion's life, such as
the antelopes or zebras that are preyed upon, and the
human hunter to whom the lion itself may fall a victim.
In addition, there are the contrasted influences of inor-
ganic nature which demand certain adjustments of the
lion's activities. Light and darkness, heat and cold, and
other factors have their direct and larger or smaller
effects upon the life of a lion, although these effects
are less obvious in this instance than in the case of
lower organisms.

The reality of variations due to the inorganic elements
of the environment is everywhere evident. Those
who have spent much time in the sun are aware that
sunburn may result as a product of a factor of this
class. The amount of sunlight falling upon a forest
will filter through the tree-tops so as to cause some
of the plants beneath to grow better than others, thus
bringing about variations among individuals that may
have sprung from the myriad seeds of a single parent
plant. In times of prolonged drought, plants cannot
grow at the rate which is usual and normal for their
species, and so many variations in the way of inhibited
development may arise.

Then there are the variations of a second class, more
complex in nature than the direct effects of environ-
ment,— namely, the functional results of use and disuse.

EVOLUTION AS A NATURAL PROCESS 113

A blacksmith uses his arm muscles more constantly
than do most other men, and his prolonged exercise
leads to an increase of his muscular capacity. All
of the several organic systems are capable of consider-
able development by judicious exercise, as every one
knows. If the functional modifications through use
were unreal, then the routine of the gymnasium and
the schoolroom would leave the body and the mind as
they were before. Furthermore, we are all familiar
with the opposite effects of disuse. Paralysis of an
arm results in the cessation of its growth. When a
fall has injured the muscles and nerves of a child's
limb, that structure may fail to keep pace with the
growth of the other parts of the body as a result
of its disuse. These are simple examples of a wide
range of phenomena exhibited everywhere by an-
imals and even by the human organism, demonstrat-
ing the plasticity of the organic mechanism and
its modification by functional primary factors of
variation.

But by far the greater number of variations seem
to be due to the so-called congenital causes, which are
sharply contrasted with the influences of the first
and second classes. It is quite true that the influences
of the third class cannot be surely and directly demon-
strated like the others, but however remote and vague
they themselves may appear to be, their effects are
obvious and real, while at the same time their effects
are to be clearly distinguished from the products of
the other two kinds. Congenital factors reside in
the physical heritage of an organism, and their results
are often evident before an individual is subjected

114 DOCTRINE OF EVOLUTION

to environmental influences and before it begins to
use its various organs. For example, it is a matter of
common observation that a child with light hair and
blue eyes may have dark-eyed and brown-haired
parents. The fact of difference is a phenomenon of
variation; the causes for this fact cannot be found
in any other category than that comprising the
hereditary and congenital influences of parent upon
offspring. How the effect is produced by such causes
is less important in the present connection than the
natural fact of congenital variation. Science, however,
has learned much about the causes in question, as we
shall see at a later point.

Thus the first step which is necessary for an
evolution and transformation of organic mechanisms
proves to be entirely natural when we give only
passing attention to certain obvious phenomena of
life. The fact of '^becoming different" cannot be
questioned without indicting our powers of observa-
tion, and we must believe in it on account of its
reality, even though the ultimate analysis of the way
variations of different kinds are produced remains for
the future.

Having learned that animals are able to change in
various ways, the next question is whether variations
can be transmitted to future generations through the
operation of secondary factors. Long ago Buffon
held that the direct effects of the environment are im-
mediately heritable, although the mode of this in-
heritance was not described ; it was simply assumed
and taken for granted. Thus the darker color of the
skin of tropical human races would be viewed by Buffon

EVOLUTION AS A NATURAL PROCESS 115

as the cumulative result of the sun's direct effects.
Lamarck laid greater stress upon the indirect or func-
tional variations due to the factors of use and disuse,
and he also assumed as self-evident that such effects
were transmissible as '^acquired characters." This
expression has a technical significance, for it refers to
variations that are added during individual life to
the whole group of hereditary qualities that make any
animal a particular kind of organism. If evolution
takes place at all, any new kind of organism originating
from a different parental type must truly acquire its
new characteristics, but few indeed of the variations
appearing during the lifetime of an animal owe their
origin to the functional and environmental influences,
whose effects only deserve the name of '' acquired
characters" in the special biological sense.

In sharp contrast to Lamarckianism, so called, — al-
though it did not originate in the mind of the noted
man of science whose name it bears, — is the doctrine
of natural selection, first proposed in its full form by
Charles Darwin. This doctrine presents a wholly
natural description of the method by which organisms
evolve, putting all of the emphasis upon the congenital
causes of variation, although the reality of other kinds
of change is not questioned. But the contrast between
Darwinism and the other descriptions of secondary
factors can best be made after a somewhat detailed
discussion of the former, which has gained the adhe-
rence of the majority of the naturalists of to-day.
However, we must not pass on without pointing out that
however much the explanations given by various men
of science may differ, they all agree in expressly recog-

\

116 DOCTRINE OF EVOLUTION

nizing the complete naturalness of the secondary as
well as of the primary factors of evolution.

The doctrine of natural selection forms the best
basis for the detailed discussion of the way evolution
has come about in the past and how it is going on
to-day. This is true because it was the first descrip-
tion of nature's program to carry conviction to the
scientific world, and because its major elements have
stood the test of time as no other doctrine has done.
Much has been added to our knowledge of natural
processes during post-Darwinian times, and new dis-
coveries have supplemented and strengthened the
original doctrine in numerous ways, although they have
corrected certain of the minor details on the basis of
fuller investigation.

At the outset it must be clearly understood that
Darwin's doctrine is concerned primarily with the
method and not with the evidences as to the actual
fact of evolution. Most of those who are not familiar
with the principles of science believe that Darwin
discovered this process ; but their opinion is not correct.
The reality of natural change as a universal attribute
of living things had been clearly demonstrated long
before Darwin wrote the remarkable series of books
whose influence has been felt outside the domains of
biology and to the very confines of organized knowl-
edge everywhere. The ^^ Origin of Species" was pub-
lished in 1859, and only the last of its fourteen chapters
is devoted to a statement of the evidence that evolution
is true. In this volume Darwin presented the results

EVOLUTION AS A NATURAL PROCESS 117

of more than twenty-five years of patient study of
the phenomena of nature, utiHzing the observations
of wild life in many regions visited by him when he was
the naturalist of the "Beagle'' during its famous voy-
age around the world. He also considered at length
the results of the breeder's work with domesticated
animals, and he showed for the first time that the
latter have an evolutionary significance. Because
his logical assembly of wide series of facts in this and
later volumes did so much to convince the intellectual
world of the reasonableness of evolution, Darwin
is usually and wrongly hailed as the founder of the
doctrine. It is interesting to note in passing that
Alfred Russel Wallace presented a precisely similar
outline of nature's workings at about the same time
as the statement by Darwin of his theory of natural
selection. But Wallace himself has said that the
greater credit belongs to the latter investigator who
had worked out a more complete analysis on the basis
of far more extensive observation and research.

The fundamental point from which the doctrine of
natural selection proceeds is the fact that all creatures
are more or less perfectly adapted to the circumstances
which they must meet in carrjdng on their lives ; this is
the reason why so much has been said in earlier con-
nections regarding the universal occurrence of organic
adaptation. An animal is not an independent thing;
its life is intertwined with the Hves of countless other
creatures, and its very living substance has been built
up out of materials which with their endowments
of energy have been wrested from the environment.
Every animal, therefore, is engaged in an unceas-

(

118 DOCTRINE OF EVOLUTION

ing struggle to gain fresh food and new energy,
while at the same time it is involved in a many-
sided conflict with hordes of lesser and greater
foes. It must prevail over all of them, or it must
surrender unconditionally and die. There is no com-
promise, for the vast totality we individualize as the
environment is stern and unyielding, and it never
relents for even a moment's truce.

To live, then, is to be adapted for successful warfare ;
and the question as to the mode of origin of species
may be restated as an inquiry into the origin of the
manifold adaptations by which species are enabled to
meet the conditions of life. Why is adaptation a
universal phenomenon of organic nature ?

The answer to this query given by Darwinism may
be stated so simply as to seem almost an absurdity. It
is, that if there ever were any unadapted organisms,
they have disappeared, leaving the world to their more
efficient kin. Natural selection proves to be a continu-
ous process of trial and error on a gigantic scale, for
all of living nature is involved. Its elements are clear
and real ; indeed, they are so obvious when our attention
is called to them that we wonder why their effects
were not understood ages ago. These elements are
(1) the universal occurrence of variation, (2) an excessive
natural rate of multiplication, (3) the struggle for
existence entailed by the foregoing, (4) the consequent
elimination of the unfit and the survival of only those
that are satisfactorily adapted, and (5) the inheritance
of the congenital variations that make for success in
the struggle for existence. It is true that these elements
are by no means the ultimate causes of evolution, but

EVOLUTION AS A NATURAL PROCESS 119

their complexity does not lessen their validity and
efficiency as the immediate factors of the process.

Taking up the first proposition, we return to the
subject of variation that has been discussed previously
for the purpose of demonstrating its reality. The
observations of every day are enough to convince us
that no two living things are ever exactly alike in all
respects. The reason is that the many details of organic
structure are themselves variable, so that an entire
organism cannot be similar to another either in material
or in functional regards, while furthermore it would
be impossible for an animal to be related to environ-
mental circumstances in the same way as another
member of its species unless it was possible for two
things to occupy the same space at the same time !
Individual differences in physical constitution are
displayed by any litter of kittens, with identical parents ;
it needs only a careful examination to find the varia-
tions in the shape of the heads, the length of their
tails, and in every other character. Sometimes the
differences are less evident in physical qualities than
in disposition and mental make-up, for such variations
can be found among related kittens just as surely as
among the children belonging to a single human family.

Not only do all organisms varx-jiut they^-seem to
vary in somewhat similar ways. While modern investi-
gations have thrown much hght upon the relations be-
tween variations and their causes, of particular value
in the case of the congenital phenomena, the greatest
advance since Darwin's time consists in the demon-

/

120 DOCTRINE OF EVOLUTION

stration by the naturalists who have employed the
laborious methods of statistical analysis that the laws
according to which differences occur are the same where-
ever the facts have been examined. A single illustra-
tion will suffice to indicate the general nature of this
result. If the men of a large assemblage should group
themselves according to their different heights in inches,
we would find that perhaps one half of them would
agree in being between five feet eight inches and five
feet nine inches tall. The next largest groups would
be those just below and above this average class, —
namely, the classes of five feet seven to eight inches
and five feet nine to ten inches. Fewer individuals
would be in the groups of five feet five to six inches and
five feet ten to eleven inches, and still smaller numbers
would constitute the more extreme groups on opposite
sides of these. If the whole assemblage comprised a
sufficient number of men, it would be found that a
class with a given deviation from the average in one
direction would contain about the same number of
individuals as the class at the same distance from the
average in the opposite direction. Taking into account
the relative numbers in the several classes and the
various degrees to which they depart from the average,
the mathematician describes the whole phenomenon
of variation in human stature by a concise formula
which outhnes the so-called ^' curve of error." From
his study of a thousand men, he can tell how many
there would be in the various classes if he had
the measurements of ten thousand individuals, and
how many there would be in the still more ex-
treme classes of very short and very tall men

EVOLUTION AS A NATURAL PROCESS 121

which might not be represented among one thousand
people.

It is not possible to explain why variation should
follow this or any other mathematical law without
entering into an unduly extensive discussion of the
laws of error. The mathematicians themselves tell
us in general terms that the observations they describe
so simply by their formulae follow as the result of
so-called_chance, by which they mean that the combined
operations numerous, diverse, and uncorrected factors
brings about this result, and not, of course, that there
is such a thing as an uncaused event or phenomenon.

Whenever any extensive series of like organisms has
been studied with reference to the variations of a
particular character, the variations group themselves so
as to be described by identical or similar curves of error.
It is certainly significant that this is true for such
diverse characters, cited at random from the hsts of
the Hterature, as the number of ray-flowers of white
daisies, the number of ribs of beech leaves, and of the
bands upon the capsules of poppies, for the shades of
color of human eyes, for the number of spines on the
backs of shrimps, and for the number of days that
caterpillars feed before they turn into pupae.

To sunamarize the foregoing facts, we have learned
that variation is universal throughout the living world,
and that the primary factors causing organic dif-
ference — the counterparts of human ingenuity in
the case of dead mechanisms — are the natural in-
fluences of the environment, of organic physiological
activity, and of congenital inheritance. These factors
are accorded different values in the evolution of new

122 DOCTRINE OF EVOLUTION

species, as we may see more clearly at a later juncture,
but the essential point here is that they are not un-
real, although they may not as yet be described by
science in final analytical terms.

We come now to the second element of the whole
process of evolution, namely, what we may call over-
production or excessive multiplication. Like varia-
tion and so many other phenomena of nature, this is
so real and natural that it escapes our attention until
science places it before us in a new light. The normal
rate of reproduction in all species of animals is such
that if it were unchecked, any kind of organism would
cumber the earth or fill the sea in a relatively short
time. That this is universally true is apparent from
any illustration that might be selected. Let us take
the case of a plant that lives for a single year, and that
produces two seeds before it withers and dies; let us
suppose that each of these seeds produces an adult
plant which in its turn lives one year and forms two
seeds. If this process should continue without any
interference, the twentieth generation after as many '
years would consist of more than one million descen-
dants of the original two-seeded annual plant, pro- /
vided only that each individual of the intervening
years should live a normal life and should multiply!
at the natural rate. But such a result as this is rendered
impossible by the very nature which makes annual
plants multiply in the way they do. Let us take the
case of a pair of birds which produce four young in
each of four seasons. Few would be prepared for the

EVOLUTION AS A NATURAL PROCESS 123

figures enumerating the offspring of a single pair of
birds at the end of fifteen years, if again all individuals
lived complete and normal lives : at the end of the
time specified there would be more than two thousand
millions of descendants. The English sparrow has been
on this continent little more than fifty years ; it has
found the conditions in this country favorable be-
cause few natural enemies like those of its original home
have been met, and as a conseciuence it has multi-
plied at an astounding rate so as to invade nearly all
parts of North America, driving out many species
of song birds before it. About twenty years ago
David Starr Jordan wrote that if the English sparrow
continued to multiply at the natural rate of that time,
in twenty years more there would be one sparrow to
every square inch of the state of Indiana ; but of course
nature has seen to it that this result has not come
about. A single conger-eel may produce fifteen million
eggs in a single season, and if this natural rate of
increase were unchecked, the ocean would be filled
solid with conger-eels in a few years. Sometimes a
single tapeworm, parasitic in the human body, will
produce three hundred million embryos ; the fact
that this animal is relatively rare diverts our attention
from the alarming fertility of the species and the ex-
cessive rate of its natural increase. Perhaps the most
amazing figures are those established by the students
of bacteria and other micro-organisms. Many kinds
of these primitive creatures are known where the
descendants of a single individual will number sixteen
to seventeen millions after twenty-four hours of develop-
ment under ordinarily favorable conditions. Though

124 DOCTRINE OF EVOLUTION

/ a single rodlike individual taken as a starting-point
may be less than one five-thousandth of an inch in
length, under natural circumstances it multiplies at a
rate which within five days would cause its descendants
to fill all the oceans to the depth of one mile. This is a
fact, not a conjecture; the size of one organism is
known, and the rate of its natural increase is known,
so that it is merely a matter of simple arithmetic to
find out what the result would be in a given time.

Even in the case of those animals that reproduce more
slowly, an overcrowding of the earth would follow in
a very short time. Darwin wrote that even the slow-
breeding human species had doubled in the preced-
ing quarter century. An elephant normally lives to
the age of one hundred years ; it begins to breed at the
age of thirty, and usually produces six young by the
time it is ninety. Beginning with a single pair of
elephants and assuming that each individual born
should live a complete life, only eight hundred years
would be requisite to produce nineteen million elephants ;
a century or two more and there would be no standing
room for the latest generation of elephants. It is only
too obvious that such a result is not realized in nature,
but it is on account of other natural checks, and not
because the natural rate of reproductive increase is
anything but excessive.

The third element of the process of natural selection
is the struggle for existence which is to a large extent
the direct consequence of over-multiplication. Be-
cause nature brings more individuals into existence

EVOLUTION AS A NATURAL PROCESS 125

than it can support, every animal is involved in many-
sided battles with countless foes, and the victory is
sometimes with one and sometimes with another par-
ticipant in the conflict. A survivor turns from one
vanquished enemy only to find itself engaged in mortal
combat with other attacking forces. Wherever we
look, we find evidence of an unceasing struggle for
life, and an apparently peaceful meadow or pond is
often the scene of fierce battles and tragic death that
escape our notice only because the contending armies
are dumb.

A community of ants, often comprising more in-
dividuals than an entire European state, depends
for its national existence upon its ability to prevail
over other communities with which it may engage in
sanguinary wars where the losses of a single battle
may exceed those of Gettysburg. The developing
conger-eels find a host of enemies which greatly de-
plete their numbers before they can grow even into
infancy. An annual plant does not produce a million
living offspring in twenty years because seeds do not
always fall upon favorable soil, nor do they always
receive the proper amount of sunlight and moisture,
or escape the eye of birds and other seed-eating animals.
These three illustrations bring out the fact that there
are three classes of natural conditions which must
be met by every living creature if it is to succeed in
life. In detail, the struggle for existence is intra-
specific, involving some form of competition or rivalry
among the members of a single species ; it is inter-
specific, as a conflict is waged by every species with
other kinds of living things; and finally it involves

f

i

126 DOCTRINE OF EVOLUTION !

an adjustment of life to inorganic environmental in-
fluences. While it may seem unjustifiable to speak of j
heat and cold and sunlight as enemies, the direct
effects produced by these forces are to be reckoned |
with no less certainty than the attacks of living foes. |

The three divisions of the struggle for existence are i

so important not only in purely scientific respects, i

but also in connection with the analysis of human i

biology, that we may look a little further into their ;

details, taking them up in the reverse order. Re- '■.

garding the environmental influences, the way that un- \

favorable surroundings decimate the numbers of the j
plants of any one generation has already been noted,
and it is typical of the vital situation everywhere.

English sparrows are killed by prolonged cold and snow \

as surely as by the hawk. The pond in which bacteria |

and protozoa are living may dry up, and these organisms j
may be killed by the bilKon. Even the human species
cannot be regarded as exempt from the necessity of
carrying on this kind of natural strife, for scores and

hundreds die every year from freezing and sunstroke j

and the thirsts of the desert. Unknown thousands I

perish at sea from storm and shipwreck, while the |
recorded casualties from earthquakes and volcanic

eruptions and tidal waves have numbered nearly one j

hundred and fifty thousand in the past twenty-eight j

years. The effects of inorganic influences upon all |

forms of organic hf e must not be underestimated in view ]

of such facts as these. !

In the second place, the vital struggle includes the bat-
tles of every species with other kinds of living things whose
interests are in opposition. The relations of protozoa

EVOLUTION AS A NATURAL PROCESS 127

and bacteria, conger-eels and other fish, Enghsh spar-
rows and hawks, plants and herbivorous animals, are
typical examples of the universal conflict in which all
organisms are involved in some way. Again it is only
too evident that human beings must participate every
day in some form of warfare with other species. In
order that food may be provided for mankind the lives
of countless wild organisms must be sacrificed in addi-
tion to the great numbers of domesticated animals
reared by man only that they may be destroyed. The
wolf and the wildcat and the panther have disappeared
from many of our Eastern states where they formerly
lived, while no longer do vast herds of bison and wild
horses roam the Western prairies. Because one or
another human interest was incompatible with the
welfare of these animals they have been driven out by
the stronger invaders.

That the victory does not always fall to the human
contestant is tragically demonstrated by the effects of
the incessant assaults upon man made by just one kind
y of living enemy, — the bacillus of tuberculosis. Every
year more than one hundred and twenty-five thousand
people of the United States die because they are unable
to withstand its persistent attacks ; five million
Americans now living are doomed to death at the hands
of these executioners, and the figures must be more
than doubled to cover the casualties on the human
side in the battles with the regiments of all the species
of bacteria causing disease.

The competition between and among the individuals
of one and the same species is the third part of the
struggle for existence, and it is often unsurpassed in

128 DOCTRINE OF EVOLUTION

^j^^jexocity. When two lion cubs of the same htter
begin to shift for themselves, they must naturally com-
pete in the same territory, and their contest is keener
than that which involves either of them and a young
lion born ten or fifteen miles away. The seeds of one
parent plant falling in a restricted area will be engaged in
a competitive struggle for existence that is much more
intense than many other parts of nature's warfare.
In brief, the intensity of the competition will be directly
proportional to the similarity of two organisms in
constitution and situation, and to the consequent
similarity of vital welfare. The interests of the white
man and the Indian ran counter to each other a few
hundred years ago, and the more powerful colonists
won. The assumption of the white man's burden too
often demonstrates the natural effect of diversity of
interest, and the domination of the stronger over the
weaker. In any civilized community the manufacturer,
farmer, financier, lawyer, and doctor must struggle
to maintain themselves under the conditions of their
total inorganic and social environments ; and in so far
as the object of each is to make a living for himself,
they are competitors. But the contest becomes more
absorbing when it involves broker and broker, lawyer
and lawyer, financier and magnate, because in each
case the contestants are striving for an identical meed
of success.

Although the severity of the conflict imposed by
nature is somewhat modified in the case of social
organisms, where community competes with com-
munity and nation with nation, no form of social
organization has yet been developed where the individ-

EVOLUTION AS A NATURAL PROCESS 129

ual contest carried on by the members of one commu-
nity has been done away with. It is an inexorable law
of nature that all living things must fight daily and
hourly for their very lives, because so many are brought
into the world with each new generation that there is
not sufficient room for all. No organism can escape
the struggle for existence except by an unconditional
surrender that results in death. Everywhere we turn
to examine the happenings of organic life we can find
nothing but a wearisome warfare in which it is the
ultimate and cruel lot of every contestant to admit
defeat.

ti.\

iie \

What now are the results of variation, over-multi
plication, and competition? Since some must die
because nature cannot support all that she produces,
since only a small proportion of those that enter upon
life can find a foothold or successfully meet the hordes
of their enemies, which will be the ones to survive?
Surely those that have even the slightest advantage
over their fellows will five when their companions
perish. It is impossible that the result could be other-
wise ; it must follow inevitably from what has been
described before. The whole process has its positive
and its negative aspects : the survival of the fittest
and the elimination of the unfit. Perhaps it would be
more correct to say the more real element is the nega-
tive one, for those which are least capable of meeting
their living foes and the decimating conditions of in-
organic nature are the first to die, while the others
will be able to prolong the struggle for a longer or

130 DOCTRINE OF EVOLUTION

shorter period before they too succumb. Thus the
destruction of the unfit leaves the field to the better
adapted, that is, to those that vary in such a way as to
be completely or at least partially adapted to carry on
an efficient life. In this way Darwinism explains the
universal condition of organic adjustment, showing
that it exists because there is no place in nature for
the incompetent.

Finally we come to the process of inheritance as
viewed by Darwin, and its part in the production and
perfection of new species. In every case, Darwin said,
the efficiency or inefficiency of an animal depends upon
its characteristics of an inherited or congenital nature.
Variations in these qualities provide the array of more
or less different individuals from which impersonal
nature selects the better by throwing out first the
inferior ones. An organism can certainly change in
direct response to environmental influence or by the
indirect results of use and disuse, but not unless it is
so constituted by heredity as to be able to change adap-
tively. Therefore the final basis of success in life must
be sought in the inherited constitutions of organic forms.

For the reason that the qualities which preserve an
animal's existence are already congenital, they are
already transmissible, as Darwin confended. Since"
his time much has been learned about the course of
inheritance and its physical basis, and the new discov-
eries have confirmed the essential truth of Darwin's
statement that the congenital characters only possess
a real power in the evolution of species.

EVOLUTION AS A NATURAL PROCESS 131

We must devote some time to the subject of inheri-
tance at a later juncture, but before leaving the matter
an additional point must be established here; the
selective process deals immediately with congenital
results, as the heritable characters that make for success
or failure in life, but by doing this it really selects the
group of congenital factors behind and antecedent to
their effects. For example, an ape that survives be-
cause of its superior cunning, does so because it varies
congenitally in an improved direction ; and the factors
that have made it superior are indirectly but no less
certainly preserved through the survival of their results
in the way of efficiency. Hereditary strains are thus the
ultimate things selected through the organic constitu-
tions that they determine and produce.

Natural selection, as the whole of this intricate
process, is simply trial and error on a gigantic scale.
Nature is such that thousands of varying individuals
are produced in order that a mere handful or only
one survivor may be chosen to bear the burden of carry-
ing on the species for another generation. The effect
of nature's process is judicial, as it were. We may
liken the many and varied conditions of life to as many
jurymen, before which every living thing must appear
for judgment as to its fitness or lack of it. A unani-
mous verdict of complete or partial approval must be
rendered, or an animal dies, for the failure to meet a
single vital condition results in sure destruction. Of
course, we cannot regard selection as involving anything
like a primitive conscious choice. It is because we

132 DOCTRINE OF EVOLUTION

individualize all of the complex totality of the world as
'' Nature" with a capital N that so many people un-
consciously come to think of it as a human-like personal-
ity. He who would go further and hold that all of
nature is actually conscious and the dwelling-place
of the supernatural ultimate, must beware of the logical
results of such a view. What must we think of
the ethical status of such a conscious power who
causes countless millions of creatures to come into the
world and ruthlessly compels them to battle with one
another until a cruel and tragic death ends their
existence ?

But that is a metaphysical matter, with which we
need not concern ourselves in this discussion ; the im-
portant point is that among the everyday happenings of
life are processes that are quite competent to account
for the condition of adaptation exhibited by various
animal forms. These processes are real and natural,
not imaginative or artificial, and so they will remain
even though it will become clear that much is still to
be learned about the causes of variation and the course
of biological inheritance. Darwin was the first to
contend that natural selection is but a part of nature's
method of accomplishing evolution. As such it is
content to recognize variations and does not concern
itself with the origin of modifications; it accepts
the obvious fact that congenital variations are in-
herited, although it leaves the question as to how
they are inherited for further examination. Because
the doctrine of natural selection does not profess to
answer all the questions propounded by scientific
inquisitiveness, it must not be supposed that it fails in

EVOLUTION AS A NATURAL PROCESS 133

its immediate purpose of giving a natural explanation
of how evolution may be partly accounted for.

Before proceeding to the post-Darwinian investiga-
tions that have done so much to amplify the account
of natural evolution, let us consider the contrasted
explanation given by Lamarck and his followers. As
we have stated earlier, Lamarckianism is the name given
to the doctrine that modifications other than those due
to congenital factors may enter into the heritage of
a species, and may add themselves to those already
combined as the peculiar characteristics of a particular
species. Let us take the giraffe and its long neck
as a concrete example. The great length of this
part is obviously an adaptive character, enabling the
animal to browse upon the softer leafy shoots of shrubs
and trees. The vertebral column of the neck comprises
just the same number of bones that are present in the
short-necked relatives of this form, so that we are
justified in accepting as a fact the evolution of the
giraffe's long neck by the lengthening of each one of
originally shorter vertebrae. The Lamarckian explana-
tion of this fact would be that the earliest forms in
the ancestry of the giraffe as such stretched their necks
as they fed, and that this peculiar function with its
correlated structural modification became habitual.
The slight increase brought about by any single in-
dividual would be inherited and transmitted to the
giraffes of the next generation ; in other words, an
individually acquired character would be inherited.
The young giraffes of this next generation would

134 DOCTRINE OF EVOLUTION

then begin, not where their parents did, but from an
advanced condition. Thus, by continued stretching
of the neck and by continued transmission of the
elongated condition, the great length of this part of
the body in the modern giraffe would be attained.

The explanation of natural selection would be quite
different. The Darwinian would say that all the young
giraffes of any one generation would vary with respect
to the length of the neck. Those with longer necks
would have a slight advantage over their fellows in
the extended sphere of their grazing territory. Being
better nourished than the others, they would be stronger
and so they would be more able to escape from their
flesh-eating foes, like the lion. For the reason that their
variation would be congenital and therefore already
transmissible, their offspring would vary about the ad-
vanced condition, and further selection of the longer
necked individuals would lead to the modern result.

The Lamarckian explanation encounters one grave
difficulty which is not met by the second one, in so far
as it demands some method by which a bodily change
may be introduced into the stream of inheritance.
So far, this difficulty has not been overcome, and the
present verdict of science is that the transmission of
characters acquired as the result of other than congenital
factors is not proved. It would be unscientific to say
that it cannot be proved in the future, but there are good
a priori grounds for disbelief in the principle, while
furthermore the results of experiments that have been
undertaken to test its truth have been entirely negative.
Rats and mice have had their tails cut off to see if this
mutilation would have its effect upon their young, and

EVOLUTION AS A NATURAL PROCESS 135

though this has been done for more than one hundred
successive generations the length of the tail has not
been altered. Quite unconscious of the scientific prob-
lem, many human races have performed precisely
similar experiments through centuries of time. In
some classes of Chinese, the feet of young girls have been
bound in such a way as to produce a small, malformed
foot, but this has not resulted in any hereditary dimi-
nution in the size of the feet of Chinese females.
Many other similar mutilations have been practised,
as for example, the flattening of the skull of some
North American Indians, but the deformity must be
produced again with each recurring generation. One
after another, the cases that were supposed to give
positive evidence have been reinvestigated, with the
result that has been stated above. It would seem,
therefore, that heredity and congenital modification
must play by far the greater part in the evolution
of species.

The doctrine of natural selection took form in the
mind of Darwin mainly on account of three potent
influences; these were, first, the geological doctrine
•of uniformitarianism proposed by Lyell, second, his
own observations of wild life in many lands and his
analysis of the breeder's results with domesticated
animals, and third, the writings of Malthus dealing with
overpopulation. As Darwin had read the works
of Buffon, Lamarck, and Erasmus Darwin, his grand-
father, who had written a famous treatise under the
title of ^^Zoonomia," he was familiar with the evidences

/

136 DOCTRINE OF EVOLUTION

known in his student days tending to prove that organic
evlution was a real natural process. Lyell's doctrine
of uniform geological history made an early and deep
impression upon his mind, and it led him to ask himself
whether the efficient causes of past evolution might
not be revealed by an analysis of the present workings
of nature. As naturalist of the ^^ Beagle" during its
four years' cruise around the world, Darwin saw many
new lands and observed varied circumstances under
which the organisms of the tropics and other regions
lived their lives. The fierce struggle for existence
waged by the denizens of the jungle recalled to him
the views of Malthus regarding overpopulation and
its results. These and other influences led him to
begin the remarkable series of note-books, from which
it is interesting indeed to learn how the doctrine of
natural selection began to assume a definite and per-
manent form in his mind, as year followed year, and
evidence was added to evidence. And it is a valuable
lesson to the student of science that for twenty-five years
Darwin devoted all his time to the acquisition of facts
before he gave his doctrine to the world in the famous
'^Origin of Species."

Darwin was particularly impressed by the way
mankind has dealt with the various species of domesti-
cated animals, and he was the first naturalist to
point out the correspondence between the breeder's
method of ^'artificial selection," and the world-wide
process of natural selection. As every one knows, the
breeder of race horses finds that colts vary much in their
speed; discarding the slower animals, he uses only
the swifter for breeding purposes, and so he perfects

EVOLUTION AS A NATURAL PROCESS 137

one type of horse. With other objects in view, the
heavy draught horse, the spirited hackney, and the
agile polo pony have been severally bred by exactly
the same method. Among cattle many kinds occur,
again the products of an artificial or human selection;
hornless breeds have been originated, as well as others
with wide-spreading or sharply curved horns; the
Holstein has been bred for an abundant supply of
milk as an object, while Jerseys and Alderneys excel
in the rich quality of their milk. Various kinds of
domesticated sheep and rabbits and cats also owe their
existence to the employment of the selfsame method,
unconsciously copied by man from nature; for men
have found variations arising naturally among their
domesticated animals, and they have simply substituted
their practical purposes or their fancy for nature's
criterion of adaptive fitness, preserving those that they
wish to perfect and ehminating those unfitted to their
requirements or ideas.

In the case of many of these and other examples,
wild forms still occur which seem to be like the ancestral
stock from which the domesticated forms have been
produced. All the varied forms of dogs — from mastiff
to toy-terrier, and from greyhound to dachshund and
bulldog — find their prototypes in wild carnivora like
the wolf and jackal. In Asia and Malaysia the jungle
fowl still lives, while its domesticated descendants
have altered under human direction to become the
diverse strains of the barnyard, and even the peculiar
Japanese product with tail feathers sometimes as long
as twenty feet. That far-reaching changes can be
brought about in a relatively short time is proved by

138 DOCTRINE OF EVOLUTION

the history of the game cock, which has nearly doubled

in height since 1850, while at the same time its slender

legs, long spurs, and other qualities have been perfected

for the cruel sport for which it has been bred. Again,

the wild rock pigeon seems to be the ancestral form

from which the fantail and pouter and carrier-pigeon

with their diverse characters have taken their origin.

It is true that some biologists have urged certain

K technical objections to the employment of domesticated

\ animals and their history as analogies to the processes

\ and results in wild nature. To my mind, however,

■artificial selection is truly a part of the whole process

^of natural selection. Man is but one element of the

(environment of tame forms, and his fancy or need is

' therefore one of the varied series of external criteria

that must be met if survival is to be the result ; failing

this, elimination follows as surely as under the conditions

of an area uninhabited or uninfluenced by mankind.

Congenital variation is real, selection is real, and the

heredity of the more fit modification is equally real.

Surely Darwin was right in contending that the facts

of this class amplify the conception of natural selection

developed on the basis of an analysis of wild life.

Knowing the elements of the selective process, it is
possible to analyze and to understand many significant
phenomena of nature, and to gain a clearer conception of
the results of the struggle for existence, especially when
the human factor is involved. Let us see how much
is revealed when the foregoing results are employed in
a further study of some of nature's vital situations.

EVOLUTION AS A NATURAL PROCESS 139

As a consequence of the many-sided struggle for
existence, the interrelations of a series of species will
approach a condition of equilibrium in an area where
the natural circumstances remain relatively undisturbed
for a long time. For example, among the field-mice of
one generation, just as many individuals will survive as
will be able to find food and to escape hereditary foes
such as cats and snakes and owls. The number of owls,
in their turn, will be determined by the number of
available mice and other food organisms, as well as
by the severity of the adverse circumstances that cause
elimination of the less fit among the fledglings brought
into the world. The vital chain of connections is
sometimes astonishingly long and intricate. One re-
markable illustration is given by Fiske, as an elabora-
tion of an example cited by Darwin. He points out
that the fine quality of the traditional roast beef of Eng-
land is directly determined by the number of elderly
spinsters in that country. The chain of circumstances
is as follows : the quality of the clover fields, furnish-
ing the best food for cattle, depends largely upon the
visits to the clover-blossoms by wild bees, that accom-
plish the fertilization of the flowers by carrying pollen
upon their bodies from one plant to another. Field-
mice devour the young in the nests of these bees, so if
there are few field-mice there will be many bees, and
consequently better grazing for the cattle. The number
of field-mice will vary according to the abundance
of cats, and so the number of these domestic animals will
exert an influence upon the whole foregoing chain of
forms. But, as Fiske points out, cats are the favorite
companions of elderly spinsters ; therefore, if there are

140 DOCTRINE OF EVOLUTION

many of the latter, there will be more cats, fewer field-
mice, more bees, richer clover fields, and finer cattle !
Each link is real and the whole chain is a characteristic?
example of the countless ways that the natural destinies
of living things are interrelated and intertwined. \

The reality of such organic interrelationships is
revealed with wonderful clearness in the numerous
instances where some disturbing factor has altered one
or another element of the balanced system. The
invasion of the new world by Europeans has directly
led to the partial or complete extinction of the tribes
of Indians to whom the land formerly belonged ; they
have disappeared almost entirely from our state of
New York, together with the bear and wolf and many
other species of animals that formerly existed here.
Wild horses and bison have also vanished before the
advances of civilization and the alteration of their
homes. Sometimes the extermination of one pest
has resulted in an increase in the number of another
through human interference with nature's equilibrium.
In some of our Western states, a bounty was offered for
the scalps of wolves, so as to lessen the number of these
predatory foes of sheep. But when the wolves were j^
diminished in number, their wild food-animals, the
prairie dogs, found their lot much bettered, and they
have multiplied so rapidly that in some places they
have become even more destructive than the wolves.

One of the most remarkable illustrations is that of
the rabbits introduced into Australia. This island
continent was cut off from the surrounding lands long
before the higher mammals evolved in far distant re-
gions, so that the balance of nature was worked out

EVOLUTION AS A NATURAL PROCESS. 141

without reference to animals like the rabbit. When
the first of these were introduced they found a territory
without natural enemies where everything was favor-
able. They promptly multiplied so rapidly that within
a few years their descendants were numerous enough to
eat up practically every green thing they could reach.
Two decades ago, the single province of Queensland was
forced to expend $85,000,000 in a vain effort to put
down the rabbit plague. The remarkable statement has
been made that in some places nature has taken a hand
in causing a new type of rabbit to evolve. Finding the
situation desperate, some of the animals have begun
to develop into tree-climbing creatures. The animals
exist in such numbers that the available food upon the
ground is insufficient for all, and so some elimination
results. But the young rabbits with longer claws,
varying in this way on account of congenital factors,
have an advantage over their fellows because they
can climb some of the trees and so obtain food inac-
cessible to the others. If the facts are correctly
reported, and if the process of selection on the basis
of longer claws and the climbing habit is continued,
the original type of animal is splitting up into a form
that will remain the same and live upon the ground,
and another that will be to all intents and purposes
a counterpart of our familiar squirrel. All the evi-
dence goes to show that squirrels have evolved from
terrestrial rodents; if the data relating to Australian
rabbits are correct, nature is again producing a
squirrel-like animal by evolution in a region where
the former natural situation has been interfered with
by man.

142 DOCTRINE OF EVOLUTION

The laws of biological inheritance have received
close and deep study by numerous investigators of
Darwinian and post-Darwinian times, because from
the first it was clearly recognized that a complete
description of nature's method of accomplishing evolu-
tion must show how species maintain the same general
characteristics from generation to generation, and also
how new qualities may be fixed in heredity as species
transform in the course of time. Before our modern
era in biology, the fact of inheritance was accepted as
self-sufficient ; now much is known that supplements
and extends the incomplete account given by natural
selection of the way evolution takes place.

It is not possible in the present brief outline to de-
scribe all the results of recent investigations, but som.e
of them are too important to be passed over. Perhaps
the most interesting one is that the laws of heredity
seem to be the same for man and other kinds of living
creatures, as proved by Galton and Pearson and many
others who have dealt with such characters as human
stature, human eye color, and an extensive series of
the peculiarities of lower animals and even of plants.

The researches dealing with the physical basis of in-
heritance and its location in the organism have yielded
the most striking and brilliant results. Darwin him-
self realized that the doctrine of natural selection was
incomplete, as it accepted at its face value the inherit-
ance of congenital racial qualities without attempting
to describe the way an egg or any other germ bears
them, and he endeavored to round out his doctrine of
selection by adding the theory of pangenesis. Accord- -\
ing to this, every cell of every tissue and organ of the

f

EVOLUTION AS A NATURAL PROCESS 143

body produces minute particles called gemmules, which
partake of the characters of the cells that produce
them. The gemmules were supposed to be transported
throughout the entire body, and to congregate in the
germ-cells, which in a sense would be minute editions
of the body which bears them, and would then be
capable of producing the same kind of a body. If
true, this view would lead to the acceptance of
Lamarck's or even Buffon's doctrine, for changes in-
duced in any organ by other than congenital factors
could be impressed upon the germ-cell, and would
then be transported together with the original specific
characters to future generations. Darwin was indeed
a good Lamarckian. . ..

But the researches of post-Darwinians, and especially
those of the students of cellular phenomena, have dem-
onstrated that such a view has no real basis in fact.
Many naturalists, like Naegeli and Wiesner, were
convinced that there was a specific substance concerned
with hereditary qualities as in a larger way protoplasm
is the physical basis of life. It remained for Weismann
to identify this theoretical substance with a specific
part of the cell, namely, the deeply staining substance,
or chromatin, contained in the nucleus of every cell.
Bringing together the accumulating observations of
the numerous cytologists of his time, and utilizing them
for the development of his somewhat speculative theo-
ries, Weismann published in 1882 a volume called '^The
Germ Plasm," which is an immortal foundation for
all later work on inheritance. The essential principles
of the germ-plasm theory are somewhat as follows.
The chromatin of the nucleus contains the determinants

144 DOCTRINE OF EVOLUTION

of hereditary qualities. In reproduction, the male
sex-cell, which is scarcely more than a minute mass of
chromatin provided with a thin coat of protoplasm and
a motile organ, fuses with the egg, and the nuclei of
the two cells unite to form a double body, which con-
tains equal contributions of chromatin from the two
parental organisms. This gives the physical basis
for paternal inheritance as well as for maternal inheri-
tance, and it shows why they may be of the same or
equivalent degree. When, now, the egg divides, at
the first and later cleavages, the chromatin masses or
chromosomes contained in the double nucleus are split
lengthwise and the twin portions separate to go into
the nuclei of the daughter-cells. As the same process
seems to hold for all the later divisions of the cleavage-
cells whose products are destined to be the various
tissue elements of the adult body, it follows that all
tissue-cells would contain chromatin determinants
\ derived equally from the male and female parents.
^ As of course only the germ-cells of an adult organism

I pass on to form later generations, and as their content
of chromatin is derived not from the sister organs
of the body, but from the original fertilized egg, there is
a direct stream of the germ plasm which flows contin-
uously from the germ-cell to germ-cell through succeed-
ing generations. It would seem, therefore, that the
(various organic systems are, so to speak, sister products
in embryonic origin. The reproductive organs are not

' produced by the other parts of the body, but their cells
are the direct descendants of the common starting-
point , namely, the egg. As the cells of the reproductive
organs are the only ones that pass over and into the

EVOLUTION AS A NATURAL PROCESS 145

next and later generations, it will be evident, in the
first place, that the germ plasm of their nuclei is the
only essential substance that connects parent and off-
spring. This stream of germ plasm passes on in direct
continuity through successive generations — from egg
to the complete adult, including its own germ-cells,
through these to the next adult, with its germ-cells,
and so on and on as long as the species exists. It does
not flow circuitously from egg to adult and then to new
germ-cells, but it is direct and continuous, and appar-
ently it cannot pick up any of the body-changes of an/_
acquired nature. Now we see why individual acquisi^
tions are not transmitted. The hereditary stream of f
germ plasm is already constituted before an animal
uses its parts in adult life ; we cannot see how altera-
tions in the structure of mature body parts through use
and adjustment to the environment can be introduced /
into it to become new qualities of the species. ^

It must be clear, I am sure, that this theory supple-
ments natural selection, for it describes the physical
basis of inheritance, it demonstrates the efficiency of
congenital or germ-plasmal factors of variation in con-
trast with the Lamarckian factors, and finally in the
way that in the view of Weismann it accounts for the
origin of variations as the result of the commingling
of two differing parental streams of germ plasm.

At first, for many reasons, Weismann's theories did
not meet with general acceptance, but during recent
years there has been a marked return to many of his
positions, mainly as the result of further cytolopcal
discoveries, and of the formulation of Mendel's Law and
of De Vries's mutation theory. The first-named law

146 DOCTRINE OF EVOLUTION

was propounded by Gregor Mendel on the basis of
extensive experiments upon plants conducted during
many years, 1860 and later, in the obscurity of his
monastery garden at Altbrtinn, in Austria. It was
rescued from oblivion by De Vries, who found it buried
in a mass of literature and brought it to light when he
published his renowned Mutation Theory in 1901.
Mendelian phenomena of inheritance, confirmed and
extended by numerous workers with plants and ani-
mals, prove that in many cases portions of the streams
of germ plasm that combine to form the hereditary
content of organisms may retain their individuality
during embryonic and later development, and that they
may emerge in their original purity when the germ-cells
destined to form a later generation undergo the pre-
paratory processes of maturation. They demonstrate
also the apparent chance nature of the phenomena of
inheritance. To my mind the most striking and sig-
nificant result in this field is the demonstration that a
particular chromosome or chromatin mass determines
a particular character of an adult organism, which is
quite a different matter from the reference of all the
hereditary characters to the chromatin as a whole.
Wilson and others have brought forward convincing
proof that the complex character of sex in insects
actually resides in or is determined by particular and
definite masses of this wonderful physical basis of
inheritance.

Mendel's principles also account in the most remark-
able way for many previously obscure phenomena,
like reversion, or a case where a child resembles its
grandparent more than it does either of its parents;

EVOLUTION AS A NATURAL PROCESS 147

such phenomena are due, so to speak, to the rise to
the surface of a hidden stream of germ plasm that had
flowed for one or many generations beneath its accom-
panying currents. I beUeve that the law is replacing f
more and more the laws of Galton and Pearson, formu- I
lated as statistical summaries of certain phenomena \
of human inheritance taken en masse. According to |
Galton's celebrated law of ancestral inheritance, the
qualities of any organism are determined to the ex-
tent of a certain fraction by its two parents taken
together as a ^^ mid-parent," that a smaller defi-
nite fraction is contributed by the grandparents taken
together as a mid-grandparent, and so on to earlier
generations. But Mendel's Law has far greater defi-
niteness, it explains more accurately the cases of
alternative inheritance, and it may be shown to hold
for blended and mosaic inheritance as well.

De Vries's new ^^ mutation theory" is clearly not an
alternative but a complementary theory to natural
selection, the Weismannian and Mendelian theories.
Like these last, it emphasizes the importance of the
congenital hereditary qualities contained in the germ
plasm, though unlike the Darwinian doctrine it shows
that sometimes new forms may arise by sudden leaps
and not necessarily by the slow and gradual accumula-
tion of slight modifications or fluctuations. The
mutants like any other variants must present them-
selves before the jury of environmental circumstances,
which passes judgment upon their condition of adapta-
tion, and they, too, must abide by the verdict that
means life or death.

From what has been said of these post-Darwinian

148 DOCTRINE OF EVOLUTION

discoveries, the Lamarckian doctrine, which teaches
that acquired non-congenital characters are trans-
mitted, seems to be ruled out. I would not lead you
to believe that the matter is settled. I would say only
that the non-transmission of racial mutilations, nega-
tive breeding experiments upon multilated rats and
mice, the results of further study of supposedly trans-
mitted immunity to poisons — that all these have led
zoologists to render the verdict of ^^not proved." The
future may bring to light positive evidence, and cases
like Brown-Sequard's guinea-pigs, and results like
those of MacDougal with plants, and of Tower with
beetles, may lead us to alter the opinion stated. But
as it stands now most investigators hold that there
are strong general grounds for disbelief in the principle,
and also that it lacks experimental proof.

The explanation of natural evolution given by Dar-
winism and the principles of Weismann, Mendel, and
De Vries, still fails to solve the mystery completely,
and appeal has been made to other agencies, even
to teleology and to ^^ unknown" and '^unknowable"
causes as well as to circumstantial factors. A com-
bination of Lamarckian and Darwinian factors has
been proposed by Osborn, Baldwin, and Lloyd Morgan,
in the theory of organic selection. The theory of
orthogenesis propounded by Naegeli and Eimer, now
gaining much ground, holds that evolution takes place
in direct lines of progressive modification, and is not
the result of apparent chance. Of these and similar
theories, all we can say is that if they are true, they are

V

EVOLUTION AS A NATURAL PROCESS 149

not so well substantiated as the ones we have reviewed
at greater length.

The task of experimental zoology is to work more
extensively and deeply upon inheritance and variation,
combining the methods and results of cellular biology,
biometrics, and experimental breeding. We may safely
predict that great advances will be made during the
next few years in analyzing the method of evolution;
and that a few decades hence men will look back to
the present time as a period of transition like the
era of reawakened interest and renewed investigation
that followed the appearance of the ^^ Origin of Species."
For the present, we can justly say that evolution, so
far as it is understood, is a real and natural process.

THE PHYSICAL EVOLUTION OF THE HUMAN SPECIES

AND OF HUMAN RACES

The teachings of science that relate to the origin and
history of the human species constitute for us the most
important part of the whole doctrine of organic evolu-
tion ; and now, having completely outlined this doc-
trine as a general one, we are brought to the point
where we must deal frankly and squarely with the
insistent questions arising on all sides as to the way
that mankind is involved in the vast mechanism of
nature's order. These questions have been ignored
heretofore, in order that the natural history of animals
in general might be discussed without any interference
on the part of purely human interest and concern. It
now becomes our privilege, and our duty as well, to
employ and apply the principles we have learned in
order to understand more completely the origin of the
human body as an organic type, the history of human
races, the development of human faculty and of social
institutions7"ahd the evolution finally of even the high-
est elements of human life. These are scientific prob-
lems, and if we are to solve them we must employ
the now familiar methods of science which only yield
sure results.

We must not underestimate the many difficulties
to be encountered, for the field before us is a vast

150

EVOLUTION OF THE HUMAN SPECIES 151

territory of complex human life and of manifold human
relations. Without prolonged exercise in scientific /
methods, it is impossible to view our own kind imper- /
sonally, as we do the creatures of lower nature. Further- ;
more it seems to many that an analysis of human life
and biological history, even if it is possible, must alter
or degrade mankind in some degree; this is no more
true than that a knowledge of the principles of engineer-
ing according to which the Brooklyn Bridge has been
constructed renders that structure any different or
unsafe for travel. Man remains man, whether we are
in utter ignorance of his mode of origin, or whether we
know all about his ancestry and about the factors that
have made him human. It is because our species
appears to occupy a superior and isolated position above
the rest of nature that the mind seems reluctant to
follow the guidance of science when it conducts its
investigations into the history of seemingly privileged
human nature. And it is feared also, that if evolution
is proven for man as well as for all other kinds of ani-
mals, our cherished ideas and our outlook upon many
departments of human life must be profoundly affected.
This may be so, but science endeavors only to find out
the truth ; it cannot alter truth, nor does it seek to do
so. We might well wish that the world were different
in many respects and that we were free from the control
of many natural laws besides that of evolution, but if
the real is what it is, then our duty is plain before us ;
as we think more widely and deeply on the basis of
ripened experience, it becomes ever clearer that a knowl-
edge of human history gives the only sure guidance for
human Hfe.

152 DOCTRINE OF EVOLUTION

To the zoologist it seems strange that so many are
opposed to a scientific inquiry into the facts of human
evolution, and to the conclusions established by such
an inquiry, — though, to be sure, this opposition is
directly proportional to ignorance or misunderstanding
of the nature and purpose of scientific investigation and
of human evolution. The naturalist comes to view
our species as a kind of animal, and as a single one of
the hundreds of thousands of known forms of life ;
thus the question of human origin is but a small part
of organic evolution, which is itself only an episode in
the great sweep of cosmic evolution, endless in past
time and in the future. Were we some other order of
beings, and not men, human evolution would appear to
us in its proper scientific proportions, namely, as a
minute fraction of the whole progress of the world.

While the foregoing statements are true, it is never-
theless right that a close study should be made of the
particular case of mankind. No doubt much of the
naturalist's interest in nature at large is due to his
conviction that the laws revealed by the organisms of a
lower sphere must hold true for man, and may explain
many things that cannot be so clearly discerned when
only the highest type is the subject of investigation.
It is only too evident that little more than a general
outline can be given of the wide subject or group of
subjects included under the head of human evolution.
We must divide the subject logically into parts, so that
each one may be taken up without being complicated
by questions relating to topics of another category,
although the findings in any one department must
surely be of importance for comparison with the results

EVOLUTION OF THE HUMAN SPECIES 153

established in another section; for if evolution is uni-
versally true, the main conclusion in any case must
assist the investigation of another, just as comparative
anatomy and embryology supplement and corroborate
each other in the larger survey of organic evolution. As
before, the illustrations of each department of the subject
must be selected from the stock of everyday observation
and information that we already possess, for we gain
much when we realize that evolution includes all the
happenings of everyday life and thought, as well as the
occurrences of the remote past.

For the present, then, the questions relating to the
higher aspects of human life must be put aside, only
Vy that they may be taken up at the last. Social evolu-
tion likewise finds its place in a later section, after the
phenomena of mind and mental evolution receive due
attention and description. At the present juncture,
the human species presents itself as a subject for organic
analysis and classification, merely as a physical organ-
ism. Just as the study of locomotives must begin with
the detailed structure of machines in the workshop
before they can be profitably understood as working
mechanisms, so the physical evolution of mankind must
first be made intelligible before it is possible to prosecute
successfully the studies dealing with the psychology,
social relations, and higher conceptions that seem at
first to be the exclusive properties of our species.

The problems of physical evolution of man and of
men fall into two groups. Those of the first deal with
the origin of the human species as a unit, and its com-
parative relation to lower organisms, while those of
the second part are concerned with the further evolu-

154 DOCTRINE OF EVOLUTION

tion of human races that have come to be different in
certain details of structure since the human type as
such arose. In the first part, all men will be assumed
to be alike and the members of a homogeneous species
whose fundamental attributes are to be compared with
those of other animals ; only afterwards will attention
be directed to the differences, previously ignored, that
divide human beings into well-marked varieties. It
must be evident even at this point that the mode of
evolution demonstrated by the first investigation will
be likely to bear some close relation to the methods
by which human races have evolved to their present
diverse anatomical situations.

The foregoing classification of the problems concerned
with the nature and origin of the human species renders
it possible to restrict the immediate inquiry to a definite
and precise question. It is this : does the evidence
relating to the physical characteristics of our species
prove that man is the product of a supernatural act of
creation, or does it show that man's place in nature has
been reached by a gradual process of natural evolution ?
In order to obtain an equally precise and definite
answer to this question, referring to the particular case
of most concern to us, it is obvious that the method to
be employed is the one which has given us an under-
standing of organic evolution as an all-inclusive natural
process. The data must be verified, related, and classi-
fied, so that their meaning may be concisely stated in
the form of scientific principles. What are the facts
of human structure, comparatively treated? How

EVOLUTION OF THE HUMAN SPECIES 155

does the human body develop? Does palaeontology
throw any light on the antiquity of man? Do the
rules of nature's order control the lives of men? Our
course is now clear; we shall take up serially the
anatomy, embryology, and fossil history of the human
species, in order to see that there is ample proof of the
actual occurrence of evolution, and then, as before,
we may look about for the causes which have produced
this result by natural methods.

While it is necessary to treat the subject directly,
namely, by examining the actual evidences relating
to the particular case in question, it is worthwhile before
doing so to point out that, as the whole includes a part,
human evolution has already been proved beyond
question. This conclusion must be accepted, unless
reasons can be given for excluding mankind from the
rest of the living world as an absolutely unique type,
supreme and isolated because of some peculiar endow-
ments not shared with the rest of animate nature. If
these reasons are lacking, and the unity of organic
nature be recognized, human evolution cannot be denied
unless some interpretation more reasonable and logical
than evolution can be given for the whole mass of facts
exemplified and discussed in the foregoing chapters.
We may accordingly approach the main questions by
asking if there are any reasons for regarding the human
species as a unique and isolated type of organism.

At the outset, we must recognize that in so far as
the human body is material, its movements and mass
relations are controlled by physical principles, like all
other masses of matter. It is well, indeed, that this is so,
for if gravitation and the laws of inertia were not con-

156 DOCTRINE OF EVOLUTION

sistent and reliable principles holding true at all times
and not intermittently, it would be difficult to order our
lives with confidence. In the next place, the general
principles of biology hold true for the structure and
physiology of the human species as they do for all other
living things. A human body is composed of eight
systems of organs, whose functions are identical with
the eight vital tasks of every other animal. All these
organs are made up of cells as ultimate vital units,
and the materials of which human cells are composed
belong to the class of substances called protoplasm.
Human protoplasm, like all other living materials,
must replenish itself, and respire and oxidize in obedi-
ence to biological laws that have been found to be uni-
form everywhere. Thus the human organism is no
more unique in fundamental organic respects than it is
apart from the world of physical processes and laws.

How does the matter stand when the general struc-
tural plan of a human being is examined ? Is it entirely
different from everything else ? It is a fact of common
knowledge that the human body is supported by a
bony axis, the vertebral column, to which the skull is
articulated and to which also the skeletal framework of
the limbs is attached. These characteristics place man
inevitably among the so-called vertebrata; he is cer-
tainly not an invertebrate, nor is the basic structure of
his body such that a third group, outside the inverte-
brata and vertebrata, can be made to include only the
single type — man.

Passing now to the classes that make up the group of
vertebrates, we meet first the lampreys or cyclostomes
without jaws, and the others with jaws, such as the

EVOLUTION OF THE HUMAN SPECIES 157

fishes, amphibia, reptiles, birds, and mammals, each class
distinguished by certain definite characters in addition
to the vertebral column. The fishes have gills and
scales ; amphibia of to-day are scaleless, and they are
provided with gills when they are young and lungs as
adults ; reptiles have scales and lungs ; birds are warm-
blooded and feathered ; while mammals are warm-
blooded and haired. Is the human species a unique
kind of vertebrate, or does it find a place in one of these
classes ? The occurrence of hair, of a four-chambered
heart which propels warm blood, of mammary glands,
and of other systematic characters marks this species
as a kind of mammal and not as a vertebrate in a section
by itself.

The members of the class mammalia differ much
among themselves ; and now that we recognize clearly
that man is a mammalian vertebrate, the next question
is whether an order exists to which our type must be
assigned, or whether we have at last reached a point
where it is justifiable to establish an isolated division
to contain the human species alone. We are familiar
with many representatives of different mammalian
orders and with the kind of structural characteristics
that serve as convenient distinctions in denoting their
relationships. Horses and cattle, sheep, and goats and
pigs resemble one another in many respects besides their
hoofs, and they form one natural order ; the well-
developed gnawing teeth of rats and rabbits and
squirrels place these forms together in the order roden-
tia ; the structures adapting their possessors for a flesh-
eating and predatory life unite the tribes of the lion,
wolf, bear, and seal, in the order carnivora. Among

158 DOCTRINE OF EVOLUTION

these and other orders of mammaUa is one to which the
lemurs, monkeys, and apes are assigned, because all
these forms agree in certain structural respects that
place them apart from the other mammalia, in the same
way, for example, that the races of white men may be
recognized as a group distinct from the black and red
races. But comparative studies, prosecuted not only
by those who have been forced to adopt the evolutionary
interpretation, but also by believers in special creation
like Linnaeus and Cuvier and other more modern oppo-
nents of evolution, have shown that the peculiar qual-
ities of this order are shared by the human species.
Indeed, the name of primates was given to this section
by Linnaeus himself, because the human body found a
place in the array which begins at the lower extreme
with the lemurs and the monkeys and ends with man
at the other end. Again it is found that no separate
order of mammals exists to include only the genus
Homo.

To one unacquainted with the facts of vertebrate
comparative anatomy, the distinguishing character-
istics of the primates seem to be trivial in nature. It
is surprising to find how insignificant are the details
to which appeal must be made in order to draw a line
between our own division of mammalia and the others.
It is well to review them as they are given in the stan-
dard text-books of comparative anatomy. Primates
are eutheria, or true mammalia possessing a placental
attachment of the young within the parent. The first
digits, namely, the ''great toe " and the ''thumb," are
freely movable and opposable to the others, so that the
limbs are prehensile and clasping structures ; usually

EVOLUTION OF THE HUMAN SPECIES 159

but not always the animals of this order are tree-dwellers
in correlation with the grasping powers of the feet
and hands. The permanent teeth succeed a shorter
series of so-called ^^milk teeth," and they are diverse
in structure, being incisors, canines, or '^ eye teeth,"
premolars, and molars ; the particular numbers of each
kind are almost invariable throughout the order and
markedly different from those of other orders. The
number of digits is always five, and with few exceptions
they bear nails instead of claws. The clavicles, or
^'collar bones," are well developed in correlation with
the prehensile nature of the fore limbs ; a bony ring
surrounds the orbit or eye socket. Finally there are
two mammary glands by which the young are suckled.
It is because any other details of difference between
man and other forms are far less marked than the
agreements in these respects, that the human species
must be regarded as a primate mammalian vertebrate.

The comparative study of the human organism as a
structural type has now been narrowed down to a review
of the various members of the order of primates. It is
the duty of science to arrange these organisms accord-
ing to the minor differences beneath the agreements in
major qualities, and to show how they are related in an
order of evolution. It will appear, when this is done,
that the supreme place is given to the human species
on account of four and only four characteristics ; these
are (1) an entirely erect posture, (2) greater brain devel-
opment, (3) the power of articulate speech, and (4) the
power of reason. As we are treating the human body

160 DOCTRINE OF EVOLUTION

as a subject for comparative structural study, the third
and fourth characters do not concern us here ; but it is
well to point out that they depend entirely upon the
second, and that they are the functional concomitants
of the improved type of brain belonging to the highest
type. Two characters remain, and in both cases it is
significant that differences in degree only are to be
found by even the closest analysis. The human brain
is the same kind of brain that lower primates possess ;
its structure is unique in no general respect. And as
regards the first-mentioned character, comparative
anatomy shows, in the first place, that this also is
something differing only in degree, and in the second
place, that it is due directly to the development of the
brain. For these reasons a survey of the various
members of the order of primates must deal largely
with the progressive elaboration of the brain and the
entailed effects of this enlargement.

The order of primates is subdivided as follows : —

Sub-order 1. PROSIMIL Lemurs.
Sub-order 2. ANTHROPOIDEA.

Family 1. Hapalidce. The marmosets.

Family 2. Cehidce. The American or tailed

monkeys.
Family 3. Cercopithecidce. The baboons.
Family 4. Simiidce. The true apes.
Family 5. Hominidce. The human species.

Each one of these subdivisions is interesting in its
own way, either because its members depart from the
typical condition of the whole order in some respects,
or because of some character that foreshadows and leads

EVOLUTION OF THE HUMAN SPECIES 161

to a more developed element of the animals placed in
the higher sections.

The lemurs are small animals very much like squirrels
in their general form and in their tree-climbing habits.
They live now almost exclusively on the island of
Madagascar, but palaeontology shows that they were
more widely spread at an earlier time. Their teeth
are exactly like our own, except that there is one more
premolar on each side of each jaw. The '^ fingers"
and ^Hoes" bear nails like ours, again with an exception
in the case of the second digits of the hind limbs, which
bear claws. The details of structure that set these
animals apart from all the rest of the primates are too
small to deserve comment in the present connection.

Passing to the true anthropoids, or man-like primates
and man himself, the first forms encountered are the
little marmosets, which are like the lemurs in some
ways, but in other respects they resemble the familiar
tailed monkeys. ' They are peculiar in having three
premolars and two molars on either side of both upper
and lower jaws, and also in the fact that the ''thumb"
is not opposable to the other fingers, while all the digits
except the ''great toes" bear claws instead of manlike
nails. The proportion of brain-case and face does not
differ much from that in the lemurs and even lower
forms like cats, for the brain has not increased greatly
^JpQ total mass, though the cerebrum is more conv.oluted
than in the lower forms.

The true monkeys, or Cebidae, are more interesting,
and at the same time they are much more familiar to
every one, as they are the commonest anthropoids of
the menagerie and circus. Their wonderful agility

162 DOCTRINE OF EVOLUTION

and sureness in climbing about is partly due to the per-
fect grasping power of the lower limb. To all intents
and purposes the foot is a hand ; the first toe is shorter
than the others, and its free motion is unrestricted as in
the thumb of the hand. These animals usually possess
a long tail which they can use as a prehensile organ,
curling it about the branch of a tree with hand-like
ease and grasp. When they run on all fours, they
plant the palms and soles flat upon the ground. The
feature of primary importance in a comparative sense
is the advanced structure of the skull. These anthro-
poids are much more intelligent than the lower forms,
which is a correlate of their larger and more convoluted
brains. The increase in the total bulk of the brain
has wrought considerable change, not only in the head,
but also in the relation of head to the trunk. The
cranium, or brain-case of bone, is relatively larger than
the ^'face," and it bulges upward so as to lie no longer
behind the latter as it does in the lower mammalia.
In consequence of this cranial enlargement, the face
and eyes are swung downward, as it were, so that the
line of vision is not straight ahead, but depressed below
the horizontal. In order to look to the front and to the
immediate foreground to which it is progressing or to
where its food or enemies may be, the monkey must
bend back its head ; if it is still, it finds greater ease
in the upright sitting posture which it assumes readily
and naturally.

The next division, called the Cercopithecidse, in-
cludes the baboons of the Old World. These animals
also run upon all fours, and their feet are handlike as
before, but the tail is much reduced. The general

1

EVOLUTION OF THE HUMAN SPECIES 163

appearance of the head is dogUke, and the brain-case
arches Httle more than it does in the monkeys, but the
face projects forward as a long muzzle, with terminal
nostrils close together. In some respects the baboons
stand somewhat away from the line leading from the
lower to higher anthropoids ; in other characters they
approach the latter, for in the teeth especially they are
identical with the apes and with the human species.

The Simiidae, or true apes, possess an overwhelming
importance, far beyond that of the baboons and mon-
keys. There are only four principal kinds now existing,
namely, the gibbon, orang-outang, chimpanzee, and the
gorilla, of which the first is much less familiar than the
others. The known species of gibbons occur in Indo-
China and the Malay Peninsula. The typical animal
stands about three feet high; its overarching brain-
case, enlarged in conformity with the much greater
brain development, has pushed the eyes and face still
further around underneath, so that if the animal walks
upon all fours the eyes look almost straight into the
ground. Therefore it must bend back its head at an
extremely uncomfortable angle if it is to remain upon all
four feet, but it prefers to raise itself up into the hu-
man sitting posture, or, when it walks, it stands erect
upon its hind limbs. Hence we who are accustomed
to think of ourselves as the only erect animals must
revise our opinion, for we find in the gibbon an organism
that is nearly, if not quite, as advanced in this respect
as we are. One peculiar difference may be pointed out,
— the walking gibbon stretches out its great long arms
to the sides in order to preserve its balance. The
animal seems awkward to us, perhaps, but it is possible

164 DOCTRINE OF EVOLUTION

that the human method of balancing the body by
vigorously swinging the arms might seem quite as awk-
ward to a gibbon as its grotesque posture does to us.

The orang-outang comes next in this series. It
inhabits the islands of Borneo and Sumatra, where we
find two distinct species. It is a reddish colored animal
standing about four feet four inches high, with rather
long hair. It is bulky, slow and deliberate in action,
and when it walks in a semi-erect position it rests its
knuckles upon the ground, swinging its long arms as
crutch-like supports. Like the gibbon, it does not
walk upon all four feet in the way that the monkeys and
baboons do, and we find in the still further development
of the brain and the higher arch of the cranium the
reasons for its semi-erectness. It cannot remain with
its hands and feet upon the ground and bend back its
head so as to direct its vision forward.

The chimpanzee of intertropical Africa brings us to
a still less monkey-hke and more manlike stage. This
creature attains the height of five feet, which is more
than that of some of the lower races of man. It possesses
large ears and heavy overarching brows ; its thumb
and great toe are more like those of man, though its
foot is still practically a hand. Its lower limb curves
like those of the other apes, and its soles are turned to-
ward one another ; in brief, it is naturally bow-legged,
a character that adapts it for a tree-climbing life.
This animal also is nearly, though not quite, erect.
It shows a most marked advance in the matter of the
brain, for the cerebrum is richly folded or convoluted,
and with this higher degree of physical complexity is
correlated its superior intelligence ; it is well known

EVOLUTION OF THE HUMAN SPECIES 165

that chimpanzees can be taught to wear clothing and
to use a cup and spoon and bowl hke a human child.
Indeed, in mental respects, the chimpanzee surpasses
all of the other mammalia, with the sole exception of
man. An eminent psychologist has stated that it is
about the equal, in mental ability, of a nine months'
old human infant.

The last form among the apes, the gorilla, is one that
brings us to a realization of our own human physical
degeneracy. The animal lives in West Equatorial
Africa, and it is a veritable giant in bulk, though its
height may not exceed five feet six inches. The heavy
ridges over the eyes, the upturned nostrils and triangular
nose, place it near to the orang-outang, but it is superior
to that form in its relatively greater brain-box, and in
the fact that its heavy lower jaws do not protrude so
greatly. It, too, is semi-erect, so that the line of the
vertebral axis makes an angle with the plane of the
ground of about seventy degrees. Its anterior limbs,
or arms, are again very long and bulky ; and like the
chimpanzee, it rests its knuckles upon the ground in
walking.

It is a short step further to the human organism,
whose brain has become larger and more complex, with
a corresponding advance in the functional powers of
reason and the like that owe their existence to the im-
proved structural basis. After what has been said
earlier regarding the relation between the erect attitude
in walking and the increased size of the cranial part of
the skull as compared with the face, it will not be diffi-
cult to see how inevitably the former is the result of
the latter. Should we get upon the ground upon our

166 DOCTRINE OF EVOLUTION

hands and knees in the position of a tailed monkey,
the eyes look straight into the ground, for the bulging
cranium has pushed out over the jaws and face so that
they lie under the brain-case instead of in front. A
person in this position can bend back the head so as to
look ahead, but the strain is too great for comfort.
Rising to the knees, and lifting the hands from the
ground, a feeling of ease at once succeeds that of tension.
In the course of evolution accomplished primarily by
the increase of the higher portions of the brain, the
erect position has been assumed gradually and naturally,
and to maintain it has necessitated many other changes
in skeleton and muscles; for example, the pelvis has
broadened to support the intestines, which bear down-
wards instead of upon the abdominal walls ; a double
curve has arisen in the axis of the vertebral column,
giving an easier balance to the upper part of the body
and the head. Countless structures of the human
frame testify to an originally four-footed position and to
a rotation of the longer axis through an angle of ninety
degrees, as evolution has produced the human type.

The conclusion that the human brain has made
mankind is thus established as one of fundamental
importance. Proceeding further, we learn that this
organ proves to be essentially the same as the brain
of lower primates ; it does not gain its greater size and
efficiency by the origination of wholly new and unique
parts, but solely by the further elaboration of the ones
present in lower forms. In a word, it is only a differ-
ence in degree and not in essential kind that separates
man from the apes and other primates. Human nature
is animal nature, and human structure is animal struc-

EVOLUTION OF THE HUMAN SPECIES 167

ture, for nowhere can final and absolute differences be
found. This does not mean that no differences appear,
for it would be absurd to contend that man and the
apes are identical in every respect ; but it does mean
that the resemblances are fundamental and compre-
hensive, and any details of dissimilarity are in the
degree of complexity only. The supreme place in f
nature attained by man is therefore due to progressive j
evolution in the nervous system. The other systems '
have degenerated to a greater or less degree, but
such regressive changes are more than compensated
for by the superior control exerted by the improved
brain. In purely physical and mechanical respects,
the human body is a degenerate as compared with a
gorilla; the arm of the latter is more powerful than
the lower limb of the former, while the gorilla's chest
is more than twice as broad as the human, and more
than four times as capacious. It is not through
superior physique, but by superior ability to direct the
activities of his body, that man excels in the struggle for
existence with the lower animals.

Moreover, the human body is a veritable museum of
rare and interesting relics of antiquity. This charac-
terization is justified by those vestigial and rudimentary
structures that represent organs of value to human
relatives among the lower animals, though they play a
less active part at the present time in human economy.
There is scarcely a single system that does not exhibit
many or fewer of these rudimentary structures, but only
a few need be specified. As compared with those of the

168 DOCTRINE OF EVOLUTION

apes, the human wisdom teeth are degenerate ; in the
gorilla they are cut at the same time as the other molars ;
and in the lower human races they com^e through the
gums in early youth, while in the more advanced
Caucasic races they are cut only in later life or not at
all. The reduced vermiform appendix of man, a source
of much ill health, is another structure that is a counter-
part of a relatively larger and useful part of the digestive
tract in the lower primates and other animals. Further-
more, the human tail is a reality, not a fiction. Now
and then an individual is born with a tail that may
reach a length in later life of eight or ten inches ; such
structures are, of course, abnormal. But in every nor-
mal human being there is a series of little bones at the
lower end of the vertebral column, constituting the
coccyx, and this is just where the abbreviated tail of
the ape and the still longer prehensile tail of the mon-
key arises from the body. Unless the coccyx is a tail,
what can it be? And if it does not represent a re-
duced counterpart of the tails of other mammals, what
does it represent?

Many of the vestigial structures of man appear more
clearly in infancy and in embryonic development.
The human embryo possesses a complete coat of hair,
called the lanugo, which usually disappears before birth.
This hair cannot be regarded as any less significant
than the coat of hair which the infant whale possesses ;
it means a completely haired ancestor. The elements
of this coat are arranged precisely as they are in the
apes ; upon the arm, for example, they point from
shoulder to elbow and from wrist to elbow. Unless
the anterior limb of the hairy human ancestor was held

EVOLUTION OF THE HUMAN SPECIES 169

in the position of the dimbing ape's, this arrangement
would be disadvantageous, for the hair as a rain-shed-
ding thatch would be effective only upon the upper arm,
while the hairs upon the forearm would catch the
rain. In a word, this vestigial coat indicates in the
clearest possible manner that the ancestor of the human
species was not only hairy, but also arboreal in its mode
of life.

Every human infant is bow-legged at birth, and the
natural position of its curved limbs is like that of the
gorilla's, for the soles of the feet are turned toward one
another. Again, the so-called great toe is at first shorter
than the others, and for a time it retains the power of
free movement that indicates a handlike character of
the lower limb in the ancestor. Many savage human
races, however, whose feet remain unshod, make use of
the primitive grasping power of the foot which the
higher races lose completely. An Australian and Poly-
nesian can pick up small objects with the foot very
much as we may with the hand.

Among the wonderful reminiscent characters dis-
played by the human infant is the firm clasping power
of the hand, which it possesses for a time after birth
and which enables it to hang suspended for several
minutes from a stick placed in its grasp. The muscles
which enable the infant to do this gradually dwindle,
so that the two-year-old child can hang suspended for
only a few seconds. This grasping muscle is a heritage
from the ape, where there is an obvious necessity for the
newborn individual to have a firm hold upon the hairy
coat of its tree-climbing mother. When the newborn
child hangs in this way, it bends its curved lower limbs

170 DOCTRINE OF EVOLUTION

so that the soles of the feet are turned toward one an-
other, thus increasing its resemblance to the ape.

Let us realize that these curious relics found in so
many places in the framework of man are not unique, and
that they are reduced counterparts of larger and more
valuable structures in the ape. Unless evolution is true,
they have absolutely no sensible reasons for existence.
Science prefers the evolutionary explanation of their
occurrence because this explanation is more in harmony
with the facts known about other organisms, and it is
more reasonable than any other.

When we dealt with the general doctrine of natural
transformation, it appeared that the evidence of embry-
ology was in many respects more cogent and conclusive
than that derived from the comparative study of animal
structures. In the case of man, as before, no one could
demand any surer or more convincing proof that an
organic mechanism with one structure can change into
an organic mechanism with a different structure, than
the obvious facts of development. The embryo, which
is not an infant or an adult, becomes an infant which
must work its way onward by the gradual accumula-
tion of slight changes here and there and everywhere in
its anatomy, until it becomes mature. Each and every
one of us has actually undergone the process of organic
change in becoming what we are, and we cannot deny
the reality of such a process without challenging the
evidence of our senses.

When the full import of this history is realized, and
when we look further into the nature of these prelim-

EVOLUTION OF THE HUMAN SPECIES 171

inary conditions through which the human organism
passes in development, we are forcibly impressed by
other facts than the one to which I have directed your
attention, for not only do we find natural transforma-
tion, as in the other mammals, but the embryonic stages
are marvelously similar to the earlier conditions in
other mammals. Not very long before birth the human
embryo is strikingly similar to the embryo of the ape ;
still earlier, it presents an appearance very like that of
the embryos of other mammals lower in the scale, like the
cat and the rabbit, — forms which comparative anat-
omy independently holds to be more remote relatives
of the human species. Indeed, as we trace back the still
earlier history, more and more characters are found
which are the common properties of wider and wider
arrays of organisms, for at one time the embryo exhibits
gill-slits in the sides of its throat which in all essential re-
spects are just like those of the embryos of birds and
reptiles and amphibia, as well as of other embryo mam-
mals ; and these gill-slits are furthermore like those
of the fishes which use them throughout life. All the
other organic systems exhibit everywhere the common
characteristics in which the embryos of the so-called
higher animals agree with one another and with the
adult forms among lower creatures ; the human embryo
possesses a fishlike heart and brain and primitive back-
bone, fishlike muscles and alimentary tract. Can we
reasonably regard these resemblances as indications of
anything else but a conamunity of ancestry of the forms
that exhibit them?

Yet a still more wonderful fact is revealed by the
study of the very earliest stages of individual develop-

172 DOCTRINE OF EVOLUTION

ment. The human embryo begins its very existence as
a single cell, — nothing more and nothing less ; in gen-
eral structure the human egg, like the eggs of all other
many-celled organisms, is just one of the unitary build-
ing blocks of the entire organic world. And yet the
egg may ultimately become the adult man. Does this
mean that man and all the other higher forms have
evolved from protozoa in the course of long ages?
Science asks if it can mean anything else. When the
comparative anatomist bids us look upon the wide and
varied series of adult animals lower than man as his
relatives, because they display similar structural plans
beneath their minor differences, it may be difficult at
first to obey him. But in the brief time necessary for
the human egg to develop into an adult, the entire
range is compassed from the single cell to the highest
adult we know. There are no breaks in the series
of embryonic stages like those between the diverse
adult animals of the comparative array. I do not think
we could ask nature for more complete proof that human
beings have evolved from one-cell ancestors as simple
as modern protozoa beyond the obvious facts of human
transformation during development. They at least
are real and not the logical deductions of reason ; yet
their very reahty and famiharity render us blind to the
deeper meaning revealed to us only when science places
the facts in intelligible order.

And now, in the third place, we may look to nature
for fossil evidence regarding the ancestry of our species.
Much is known about the remains of many kinds of

EVOLUTION OF THE HUMAN SPECIES 173

men who lived in prehistoric times, but we need con-
sider here only one form which lived long before the
glacial period in the so-called Tertiary times. In 1894
a scientist named Dubois discovered in Java some of the
remains of an animal which was partly ape and partly
man. So well did these remains exhibit the characters
of Haeckel's hypothetical ape-man, Pithecanthropus j
that the name fitted the creature like a glove. Spe-
cifically, the cranium presents an arch which is inter-
mediate between that of the average ape and of the
lowest human beings. It possessed protruding brows
like those of the gorilla. The estimated brain capacity
was about one thousand cubic centimeters, four hundred
more than that of any known ape, and much less than
the average of the lower human races. Even without
other characters, these would indicate that the animal
was actually a ^^ missing link" in the scientific sense,
— that is, a form which is near the common progenitors
of the modern species of apes and of man. We would
not expect to find a missing link that was actually
intermediate in all respects between modern apes and
modern men, any more than we should look for actual
connecting bands of tissue between any two leaves
upon a tree. A missing link, in the true sense, is like
a bud of earlier years which stood near the point from
which two twigs of the present day now diverge. So
Pithecanthropus is a part of the chain leading to man,
not far from the place where the human line sprang
from a lower primate ancestor.

Of the fossil remains of true prehistoric men, little
need be said. We cannot know whether the races now
living in the regions where these remains are found are

174 DOCTRINE OF EVOLUTION

really the descendants of the older types, and so a direct
comparison cannot be made. It is true that the brain
capacities of the man of Spy, of the Neanderthal, and of
the English caverns are lower than those of modern civi-
lized races, but the differences are not so striking and
not so clearly indicative of the apelike ancestor of
man as in the case of the previous comparison of
Pithecanthropus with apes and men.

The foregoing facts illustrate the conclusive evidence
brought forward by science that human evolution in
physical respects is true. Even if we wished to do so,
we cannot do away with the facts of structure and
development and fossil history, nor is there any other
explanation more reasonable than evolution for these
facts. If now we should inquire into the causes of this
process, we would find again that the present study of
man and men reveals their subjection to the laws of
nature which accomplish evolution elsewhere in the
organic world.

The fact of human variation requires no elucidation ;
it is as real for men as for insects and trees. Indeed,
some of the most significant facts of variation have been
first made out in the case of the human species. The
struggle for existence can be seen in everyday life. We
cannot doubt its reality when scores perish annually
because of their failure to withstand the extreme degrees
of temperature during midwinter and midsummer;
when starvation causes so many deaths, and when the
incessant combat with bacterial enemies alone brings
the list of casualties on the human side in our own

EVOLUTION OF THE HUMAN SPECIES , 175

country to more than two hundred and fifty thousand a
year. As in nature at large, the more unfit are elimi-
nated as a result of this struggle, while the more adapted
succeed. In the long run, that particular applicant for
a clerkship or any other work who may be the more
fitted is the one who gets it. While the severity of
competition may be somewhat mitigated as the result
of social organization, and while our altruistic charitable
institutions enable many to prolong a more or less
efficient existence, the struggle for existence cannot be
entirely done away with. Heredity also is a real human
process, and it follows the same course as in animals at
large ; as in the case of variation, some of the funda-
mental laws of its operation have been first worked out
in the case of human phenomena, and have been found
subsequently to be of general application.

Reverting to the specific question as to the earliest
divergence of man from the apes, we can readily see how
the superior development of the ape-man's brain gave
him a great advantage over his nearest competitors,
and how truly human ingenuity enabled the earliest
men to employ weapons and crude instruments instead
of brute force. Thus the gap between men and apes
widened more and more, as reasoning power increased
through successive generations. This is another aspect
of the statement that the supreme position of man has
been gained, not by superior organization in physical
respects outside of the nervous system, but by the
superior control of human organization by the higher /
organs of this system.

The unity of nature and of its processes is established
more and more surely as the naturalist classifies the

176 DOCTRINE OF EVOLUTION

facts of structure, development, fossil history, and
evolutionary method. Our own species is not unique ;
it takes its high place among other organic forms
whose lives are controlled in every way by the uniform
consistent laws of the world.

The physical evolution of human races is the next
major division of the large subject before us. Hereto-
fore the obvious differences displayed by various races
have been disregarded and the species has been treated
as a unit, in order that its evolution from pre-human
ancestors might be made clear. Knowing now how the
facts of structure show that the supreme position of
our kind has been attained mainly as the result of the
progressive elaboration of the higher portions of the
brain, and not because new and unique structures have
been developed, we are prepared to turn our attention
to the diverse characteristics of human races ; and during
this inquiry anatomical matters will still be the only
ones to be reviewed. The intellectual and social char-
acters of numerous races belong to the category of physi-
ological or functional phenomena, which are to receive
due consideration at a later time. It is the meaning
of the facts of racial diversity for which we are now
to look.

For many reasons this subject is more difficult to
describe in a concise outline than those taken up before.
It is true that every one is familiar with different types
of human beings, such as the Negro and Japanese and
Chinese, while furthermore the obvious differences
between such races as the Norwegian and Italian are

EVOLUTION OF THE HUMAN SPECIES 177

sufficiently marked to strike the attention of any one
who looks about at his fellow-passengers in a crowded
street car. But few indeed have a comprehensive
knowledge of the wider range of racial variation in
which these familiar examples find their place. Anthro-
pology, or the science of mankind, is a large and well-
organized department of knowledge, dealing with the
entire array of structural and physiological characters
of all men. One of its subdivisions, anthropometry, is
almost an independent discipline with methods of its
own ; it describes the characteristics of human races as
these are determined by statistical methods of a some-
what technical nature. There is still another science,
ethnology, which deals more particularly with institu-
tions, customs, beliefs, and languages rather than with
physical matters, although it is clear that ethnology
and anthropology cannot be sharply separated, and that
each must employ the results of the other for its own
particular purposes.

Because men have always been interested in the study
of themselves, the subject of racial evolution is literally
enormous, and the attempt to give anything like a
complete description of what is known would obviously
be futile. But it is possible to obtain a clear conception
of certain of the fundamental principles that fall into
hne with the other parts of the doctrine of organic evo-
lution with which we have now become acquainted.
The main questions, therefore, may be stated in simple
terms. The first deals with the evidences as to the
reality of evolution during the historical and prehistoric
development of the various types of man from earlier
common ancestors; the second asks whether the lines

N .

178 DOCTRINE OF EVOLUTION

of racial evolution are further continuations of the line
leading from ape-like ancestors to the human species as
a type. In order to give the proper perspective, it will
be well to state at the present juncture, first, that the
various kinds of men do not vary from each other in a
chance manner so as to show all possible types and
varieties, but that they fall into natural groups or
families distinguished by certain common character-
istics, just as do all other kinds of species of animals;
in the second place, it appears that some of the dif-
ferences between the races denoted higher on struc-
tural accounts and the lowest forms of man are of the
same nature as those observed in the review of the
various species of primates from the lemurs to man.

It is best to look at the whole question in a very simple
and common-sense way before undertaking an extended
examination of the details of human diversity. The
most casual survey of the peoples that we know best
because of our own individual nearness to them enables
us to realize that the races now upon the earth have not
existed forever and ever, or even for the age of 6000
years as contended by Archbishop Ussher. They have
all come into existence as such, and they differ from
their known antecedents ; so that at the very outset
common-sense leads us to accept evolution as true, if
we admit that human races have changed during the
course of recent centuries. We know, for example, that
the so-called Mexicans of to-day are a people produced
by a fusion of Spanish conquerors and Indian aborig-
ines ; the Mexican is neither Spaniard nor Indian, though

EVOLUTION OF THE HUMAN SPECIES 179

he may resemble both in certain respects ; he is a prod-
duct of natural evolution, accomplished in this case by
an amalgamation of two contrasted types. When we
speak of the American people, we must realize that it too
has come into existence as such, and even, indeed, that
it is in the actual process of evolution at the present
time. The various foreign elements that have been
added during the last few decades by the hundreds of
thousands are becoming merged with the people who
preceded them, just as the Dutch and the French and
the English coalesced during the days of early settlement
to form the young American nation. Perhaps most of
us call ourselves Anglo-Saxon, but we are in reality some-
what different even in physical respects from the Eng-
lishmen of Queen Elizabeth's time, who alone deserved
the name Anglo-Saxon. This very term indicates an
evolution of a type that differs from both the Angles
and the early Saxons of King Alfred's age. These are
simple examples which illustrate many features of the
universal history of human races wherever they are to
be found. Even in the comparatively peaceful times
of our modern era the history of any race is a veritable
turmoil of constant changes ; conquerors impress their
characters upon the vanquished, while the victors often
adopt some of the features of the conquered. Colonies
split off from the mother nation to follow out their
destinies under other conditions. Nowhere does the
naturalist find evidence of long-established permanence,
or an unentwined course of an uninterrupted and un-
modified line of racial descent.

It is the task of the student of human evolution to
unravel the tangled threads of human histories. The

180 DOCTRINE OF EVOLUTION

task is relatively simple when it is concerned with recent
times where the aid of written history may be sum-
moned ; but when the events of remote and prehistoric
ages are to be placed in order, the difficulties seem well-
nigh insuperable. All is not known, nor can it ever be
known ; but wherever facts can be established, science
can deal with them. By a study of the present races
of mankind, much of their earlier history can be worked
out, for their genetic relations may be determined by
employing the principle that likeness means consanguin-
ity. Let us suppose an alien visitor to reach our planet
from somewhere else ; if he were endowed with only
ordinary human common-sense, he would very soon
ascertain the common origin of the English-speaking
people in Canada, the United States, Australia and
New Zealand, South Africa, and many other places.
Even if he could not understand a word of the English
language, he would be justified in regarding them all as
the descendants of common ancestors because they
agree in so many physical qualities. The anthropologist
works according to the same common-sense principle,
obtaining results that find no explanation other than
evolution when the varying characters that are used to
determine social relationship are properly classified and
related. It is to these characters that we must now
give some attention.

The average stature of adults varies in different races
from four feet one inch in certain blacks to nearly six
feet and seven inches, as among the Patagonians.
These are the extreme values for normal averages,

EVOLUTION OF THE HUMAN SPECIES 181

although dwarfs only fifteen inches high have been
known, while ^'giants " sometimes occur with a height
of nine feet and five inches. Such individuals are of
course rare and abnormal, and are not to be taken
into account in establishing the average stature of
a race for use in comparison with that of another
group.

The color of the skin is another criterion of racial
relationship, though it is more variable in races of com-
mon descent than we are wont to assume. We are
familiar with the fair and florid skin of the northern
European, the fair and pale skin in middle and southern
Europe, the coppery red of the American Indian, the
brown of the Malay, of the Polynesian and of the Moor,
the yellowish cast of the Chinese and Japanese, and
the deeper velvety black of the Zulu ; but it has been
found that many of the close relatives of the black are
lighter in skin color than some of our Caucasian rela-
tives, so that this character cannot be taken by itself
as a single criterion of racial affinity.

Perhaps the most conservative and most reliable
character that serves for the broad classification of the
human races is the shape of the individual hairs of the
head. We are familiar with the straight lank hair of
the Mongolian peoples and of the various tribes of
American Indians, in whom the hair possesses these
peculiarities because each element grows as a nearly
perfect cylinder from the cells of the skin at the bottom
of a tiny pit or hair-follicle. The familiar wavy hair
of white men owes its character to the fact that the
individual elements are formed by the skin, not as pencil-
like rods, but as flattened cylinders. They are oval or

182 DOCTRINE OF EVOLUTION

elliptical in cross-section, and when they emerge from
the skin they grow into a long spiral. If, now, the hair
is formed as a very much flattened rod about one-half
as wide in one diameter as in the other, it curls into a
very tight close spiral and gives the frizzly or woolly
head-covering of the Papuan and of the Negro.

In the next place, the shape of the cranium is a char-
acter of much value. This is determined as the propor-
tion between the transverse diameter of the skull above
the ears to the long diameter, namely, the line that runs
from the middle of the brow to the most posterior point
of the skull. In the so-called '4ong-headed " or doli-
chocephalic races, the proportion is seventy-five to one
hundred, while in those forms that have more rounded
or brachycephalic heads, like the Polynesian and the
black pygmy, the relation is eighty-three to one hundred.
The cranial capacity again varies considerably, from
nine hundred cubic centimeters to twenty-two hundred
cubic centimeters. Many striking variations are also
found in the projection of the jaws. A line drawn
from the lower end of the nose to the chin makes a
certain angle with the line drawn from the chin to the
posterior end of the lower jaw ; if the jaw projects very
greatly, this angle will be much less than when they do
not. In most of the Caucasian peoples, the lines meet
at an angle of eighty-nine degrees, or very nearly a right
angle, but in some of the lower races the figure may be
only fifty-one degrees. Additional characters of the
teeth and of the palate are also taken into account, and
have proved their utility. Finally, the nose exhibits
a wide range of variation from the small delicate feature
of the Chinaman to the large, well-arched nose of the

EVOLUTION OF THE HUMAN SPECIES 183

Indian. It may be hollowed out at the bridge instead
of arched ; again, it may be nearly an equilateral tri-
angle in outline, as in the Veddahs, and the nostrils may
open somewhat forward instead of downward. As
many as fifteen distinct varieties of the human nose
have been catalogued by Bertillon.

These are the principal bodily characters which the
anthropologist uses to distinguish races and by their
means to determine the more immediate or remote com-
munity of origin of comparable types. Many of these
characteristics, as indeed we may already see, are de-
cidedly important in connection with the second problem
specified above, for in the case of the flat triangular
nose and projecting jaws of a low negroid we may
discern clear resemblances to certain features of the
apes.

Long before the doctrine of evolution was understood
and adopted, students of the human races had been
deeply impressed by their natural resemblances. As
early as 1672 Bernier divided human beings accord-
ing to certain of these fundamental similarities into four
groups ; namely, the white European, the black African,
the yellow Asiatic, and the Laplander. Linnseus, in
the eighteenth century, included Homo sapiens in his
list of species, recognizing four subspecies in the Euro-
pean, Asiatic, African, and Indian of America. Blu-
menbach in 1775 added the Malay, thus giving the five
types that most of us learned in our school days. But
the different varieties of men recognized by these
observers were believed to be created in their modern

184 DOCTRINE OF EVOLUTION

forms and with their present-day characteristics; the
common character of skin color exhibited by any group
of peoples of a single continent was to them only a
convenient label for purposes of description and classifi-
cation. It was not until years later that fundamental
resemblances were recognized as indicating an actual
blood relationship of the races displaying them, and
therefore of evolution. Since the doctrine of human
descent and of the divergence of human races in later
evolution has been accepted, those who have attempted
to work out fully the complete ancestry of different
peoples have found that no single character can be taken
by itself, while the various criteria themselves differ in
reliability ; the color of the skin is not so sure a guide as
the character of the hair and skull, wherefore the classi-
fications of recent times, notably those of Huxley and
Haeckel, have been based largely upon the latter. The
latest systems have been more rigidly scientific and more
in accord with the most modern conceptions of organic
relationships in general, as evidenced by the thorough-
going methods of Duckworth in his recent treatise on
human classification.

It now remains to present the salient facts regarding
the genetic relationships of typical human races,
although it is obviously impossible to go into all of the
details of the subject. But these are not essential for
the main purpose, which is to show that the evolution-
ary explanation is the only one that is reasonable and
self -consistent. Opinions are sometimes widely at
variance regarding countless minor points, but no an-
thropologist of to-day can be anything but an evolu-
tionist, because the main principles upon which the

EVOLUTION OF THE HUMAN SPECIES 185

specialists agree fall directly into line with those estab-
lished elsewhere in zoology. It seems best to state
these principles without reverting to controversial mat-
ters which find their place in the monographs of the
experts. Any comprehensive account such as that of
Keane, even if it may not give the final word, will be
entirely sufficient to demonstrate how fruitful are the
methods of evolution when they are employed for the
study of human races, and indeed how impossible it is
to discuss human histories without finding conclusive
evidences of their evolutionary nature.

The facts that are available indicate that the first
members of our species evolved in an equatorial conti-
nent which is now submerged, and which occupied a
position between the present continents of Asia and
Africa. From this center hordes of primitive men
migrated to distant centers where they differentiated
into three primary and distinct groups. The first of
these was gradually resolved into the darker-skinned
peoples most of whom now live in the continent of
Africa, although many dwell also in the islands of the
western Pacific Ocean. The second branch divided
almost immediately to produce, on the one hand, the
Indians of the new world and, on the other, the yellow-
skinned inhabitants of Asia and other places. The
third branch developed as such in the neighborhood of
the Mediterranean Sea, and produced the series of
so-called Caucasian peoples, which are by far the most
familiar to us and to which most of us belong. But
so early did the second branch divide that there are
virtually four main divisions of the human species that
are to be examined in serial order.

1§6 DOCTRINE OF EVOLUTION

It is best to begin with our own division, because its
greater familiarity makes it easier to become acquainted
with the methods and results of anthropology, on the
basis of facts that we already know. Three subordi-
nate types exist, located primarily in northern, central,
and southern Europe respectively, but many other races
dwell elsewhere that are assignable to one or another
of these subdivisions. In northeastern Europe we
find people such as the Norwegians, Swedes, Danes, and
north Germans, that average five feet eight inches in
height. They have the long, wavy, and soft hair which
is a general characteristic of the whole Caucasian
group, although its light flaxen color is distinctive.
The blue eye and florid complexion accompany the
light color of the hair. The skull is of the longer type,
the jaws and forehead are straight and square, the nose
is large and long without a distinct arch, and the teeth
are relatively small. It is not so well known that the
Scandinavian type is so closely copied by many people
of Asia, such as the western Persians, Afghans, and
certain of the Hindus, living in a continent that we are
inclined to assign to the Mongol only. In the posses-
sion of these characters the Northern Europeans and
other races specified display evidences of their common
ancestry and evolution quite as conclusively as in the
case of the cats discussed in an earlier chapter where
the meaning of essential likeness was first demonstrated.

A broad zone may be drawn from Wales, across Eu-
rope and Asia, and even to the eastern islands of the
South Seas, in which we find peoples that are obviously
of Caucasian descent, but they differ from the members
of the first group in some details of structure. On the

EVOLUTION OF THE HUMAN SPECIES 187

average they are about five feet five or six inches in
height, the hair is dark and wavy, but it is not the pencil-
like structure of the Mongol. The complexion is pale,
the skull is rounder, and the eyes are usually brown in
color. These peoples agree also in their volatile tem-
perament and vivacious manner and are thus markedly
different from the more stolid northerners. To this
minor branch of the Caucasian stock belong the Welsh,
most of the French, South Germans and Swiss, Rus-
sians and Poles, Armenians, eastern Persians, and finally
some of the inhabitants of Polynesia. The last, it is
true, form a well-marked group of darker-skinned and
taller races, but in spite of the admixture of these and
other unusual features, we can still discern the bodily
characters that supplement their traditions, telling of
an Asian origin, in demonstrating their common ances-
try with round-headed Persians and middle Europeans.
Below the zone of middle Europe and Asia is another
broad region inhabited by the '^ Mediterranean ^' type
of Caucasian. The Spaniard, Italian, Greek, and Arab
are sufficiently familiar to illustrate the distinctive
qualities of this subdivision. These people have the
smaller stature, dark hair, dark eyes, and paler skin
of the middle Europeans, but the skull is of the long
instead of the rounded type. A well-marked sub-
ordinate group is formed by the so-called Semitic
peoples, such as the Arabs and their Hebrew relatives.
The Berbers and other North African races possess a
darker skin probably because of the admixture of
Ethiopian stock, and they, too, are so well character-
ized that they form a clearly marked outlying group
as the so-called Hamites. Passing over into Asia we

188 DOCTRINE OF EVOLUTION

find relatives of the Mediterranean man in the Dravidas
and Todas of India, possibly in the degenerate Veddahs
of Ceylon, and finally in the Ainus or ^' hairy men '^
of some of the Japanese islands. The last-named
people certainly possess some Mongolian features,
but these seem to have been added to a more funda-
mental form of body that is distinctly Caucasian.

All of the races we have mentioned, together with
their relatives, may be compared to the leaves borne
upon three branches that take their origin from a single
limb of the widespread human part of the tree. They
cannot be classified in any mode on the basis of their
primary and secondary resemblances without employing
the treelike plan of arrangement, which to the man
of science is a sure indication of their evolutionary
relationships.

The people of the second or Mongolian group agree in
certain well-marked characteristics in such a way as to
be well separated from the other divisions of mankind ;
these characteristics we may speak of as constituting
a second '^ theme," of which the various peoples of the
group are so many variations. To visualize them we
need only to recall the appearance of the Chinaman,
perhaps the most familiar example of the entire series.
Here the hair is coarse and black, and straight because
of its round transverse section ; the mustache and
beard of the Caucasians are seldom found except in
later life ; the skin is a fleshy yellow in color ; the skull is
round, indeed, it is one of the roundest that we know ;
the jaws are not so straight as in the Caucasian, for

EVOLUTION OF THE HUMAN SPECIES 189

the angle at the point of the chin is about sixty-eight
degrees. The cheek bones project laterally, with greater
or less prominence ; the nose is very small, tilted up
slightly at the end, and is usually hollowed instead of
arched. The eyes are small and black in color, set
somewhat obliquely, and the upper lid is drawn down
over the eye at its inner corner so as to make the ob-
liquity still more marked. The teeth are larger than
those of the Caucasian. Finally, the Mongol is below
the average of all men as regards height, being usually
about five feet four inches tall.

The original Mongolians probably developed the
characteristic features we have just noted in a Central
Asiatic region, and then almost immediately they
divided into two great groups. Each of these evolved
along certain lines of its own, one sweeping northward
to develop into what are now called the Northern
Mongols, the other working its way eastward and south-
ward to produce the peoples of China proper, Indo-
China, and many parts of Malaysia. Considering first
the peoples of the Northern Mongolian division, we
find in the typical Manchurian what is perhaps the
nearest among modern people to the original race.
Spreading northward and westward from the middle
Asiatic plains, this great wave has produced the nomadic
tribes of Siberia, like the Chukchi, the Buryats, and the
Yukaghir. The present inhabitants of Turkestan con-
nect those forms which have remained near the original
home with the races of Mongolian origin that live
farther to the westward, like the Turks of Asia. But
the Mongolian tide originally swept much farther to the
west, although it was driven back later by conquering

190 DOCTRINE OF EVOLUTION

Caucasian peoples ; and it has left behind such rem-
nants as the Finlander and the Laplander, the Bulgar,
and the Magyar. It is evident that these western
branches of the Mongol stock are not at all pure in their
racial characteristics, for they clearly show the effects
of a mixture with alien European peoples. To assign
them to the Northern Mongol division means only that
their dominant characteristics are mainly those of
Mongolian nature. We have referred the Russians to
the middle Caucasian division even though the Slav
or Tartar infusion is very great, but it does not domi-
nate over the Caucasian peculiarities as it does in the
case of the peoples we have mentioned. As regards
the remaining types we must add to this brief list the
Koreans and the Japanese, the former being far purer
in Mongolian nature than the latter people, which has
apparently been affected by a Malay influence from
the south.

Turning now to the southern Mongol, we find that
from their cradle in the Tibetan plateau they too have
spread widely, and their descendants have also come
to differ in certain respects as they have established
themselves in other lands. Most of the present people
of Tibet belong to this section; the Gurkhas of Hin-
dustan, the people of Burma proper, of Annam, and
Cochin China are close relatives of one another and of
the more characteristic Mongolians of China proper
who make up the vast bulk of the population. From
this stock we may also derive the Malays of Sumatra
and Java, of Borneo and Celebes, and the Tagals and
Bisayans of the Philippine Islands. Even the Hovars
and other tribes of Madagascar may be referred to this

EVOLUTION OF THE HUMAN SPECIES 191

division, for although in them the skin has become
somewhat darker, we may still discern the character-
istics which indicate their common ancestry with the
Oceanic Mongols.

The American Indians taken collectively constitute
a group that is well set off from the rest of mankind by
such characters as taller stature, small, straight, and
black eyes, a large nose that is usually bridged or aqui-
line, a skull of medium roundness, and the yellow copper
color of the skin. The common origin with the Mongols
is demonstrated by the straight and long, coarse, black
hair and by the absence of a beard ; the mustache also
is almost always absent.

All of us have seen Indians belonging to the tribes
of the plains, which serve as excellent examples of this
grand division. Many have also visited the homes of
the Pueblo Indians, and have learned how uniform is
the physical appearance of the tribes living in various
parts of the United States. Indeed throughout all of
North America the basic characteristics of Indians
prove to be strikingly conservative, although in the
Eskimo there are some departures which seem to indi-
cate a closer connection of these peoples with the Mon-
gols, probably as the result of some more recent influx
from the neighboring and not very distant region of
northeastern Siberia. Extending our survey south-
ward through Central America, the Aztecs and Mayas
are found to possess many of the same characters,
though in some respects they are transitional to the
Caribs of the northern edge of South America and to

192 DOCTRINE OF EVOLUTION

the Indians of South America. TraveUng still farther
southward, we meet the very tall Patagonian, still an
Indian in essential respects, and finally, the Yahgan
and Alacaluf of the Fuegian region, the most degenerate
members of the race. The last-mentioned people are
dull and brutish and most degraded in all respects,
and stand at the lowest end of the red Indian series
as regards intellectual ability and cultural attainment.

We now come to the last of the four great divisions of
the human species which includes the races usually
spoken of as Africans or Ethiopians. But these races
are by no means restricted to the continent of Africa,
for quite as typical black types are found in far-distant
lands such as Australia and many islands of the Pacific
Ocean. The races assigned to this division group them-
selves about two subordinate types, — the tall negro
proper and the shorter or dwarf negrito, — and each of
these has representatives both in Africa and in the
oceanic territory.

The black slaves of America were all descended from
typical negros brought from the western part of Africa,
and they provide us with adequate illustrations of Ethi-
opians as a group. In them the stature is above the
average of men in general, specifically about five feet
ten inches. The short jet-black hair is strikingly dif-
ferent from the head covering of the other great groups
of human races ; each individual hair is so flat in cross-
section that it curls into a very tight close spiral, and
this brings about a frizzly appearance of the whole head
covering. There is little or no beard, the skin is soft

EVOLUTION OF THE HUMAN SPECIES 193

and velvety and of various shades approaching black
in color. The skull is long, the cheek bones are small,
but the most distinctive characteristics of the head are
found in the apelike ridges over the eyes and in the
very broad flat nose which projects only slightly and
turns up so that the nostrils open forward to a marked
degree, while in the jaws there is an astonishing diver-
gence from the Caucasian condition in the great pro-
trusion which causes the angle at the chin to be about
sixty degrees.

The warlike Zulus and other peoples of Southern and
Central Africa are perhaps the most characteristic
races in this division. Their relatives are found to the
northward as far as the Sahara desert, along the south-
ern borders of which they have spread out to the east-
ward and westward. Fusion with other races has taken
place along this border so that many of these northern
tribes are much lighter than the Zulus in the color of
the skin. But many relatives of the taller African negro
are found in other parts of the world, namely in Aus-
tralia, and in New Hebrides and New Caledonia —
islands to the north and east of this continent. The
Papuan of New Guinea is a typical negro in all true
respects, with strongly marked Ethiopian character-
istics, though there are some differences which are
transitional to the more aberrant natives of Melanesia,
which includes many archipelagos like the Fiji, Bis-
marck, Marshall, and Solomon islands. Undoubtedly
the most degenerate member of the tall negro division
is the Australian native, the so-called " blackfellow.'^
The bulbous nose and the well-grown beard mark him
off from the typical stock, but his obvious relation-

194 DOCTRINE OF EVOLUTION

ship to this is indicated by the low brain capacity, the
prominent ridges over the eyes, and the heavy pro-
jecting jaws.

Taking up the other division of the so-called Ethi-
opian race, constituting the Negrito section, we may
begin with its Oceanic members. The natives of the
Andaman Islands, the Kalangs and the Sakais of Java
and neighboring regions, and the Aetas of the Philip-
pine Islands agree in a dwarfed stature of four feet or a
little over, in their yellowish brown skin color, a round
head, and woolly reddish-brown hair. They, too, pos-
sess large ridges over the eyes and extremely prominent
jaws, and in these latter characteristics particularly we
see evidences of their relationship to the negro. But
perhaps the most characteristic pygmies are found in
Africa. The little Bushmen and Hottentots are low
types of the Negrito stock, and they lead us to the low-
est men of all, the Akkas of the West Congo region. It
is difficult for us to realize how utterly degenerate and
apelike these pygmies are. The jaws are dispropor-
tionately large as compared with the cranium or brain-
case, and project to a degree which brings the skull
very close to that of the higher apes ; while in mental
respects, in the absence of dwellings, and in many
other ways they prove to be the lowest of all mankind,
— veritable brutes in form and mode of life.

Without a full series of photographs before us the
foregoing sketch of the various races of men cannot
make us fully acquainted with all the strange varieties
of the human body, but it will suffice to establish two

EVOLUTION OF THE HUMAN SPECIES 195

fundamental results. While all men agree in the pos-
session of certain features which set them apart from
other members of the primate order, they differ among
themselves in such a way as to fall into four well-marked
subdivisions branching out from a common starting-
point. Furthermore, in each of these primary groups
the subordinate types arrange themselves also in the
manner of branches arising from a common limb.
This is the relation that we have earlier found to be a
universal one throughout the animal kingdom, and
science believes that it indicates everywhere an evolu-
tionary history — an actual development along dif-
ferent lines of descent of forms which have a common
starting-point and ancestry.

The second principle is perhaps even more significant :
when we review the many races from the Caucasian to
the dwarf Negrito, we traverse a downward path which
will bring us inevitably to the higher apes. In our
survey of human races, w^e have passed from the Cau-
casian, with the largest brain and cranium and with
straight jaws well underneath the brain-case, to the
pygmy with a relatively small brain, with huge pro-
jecting jaws and with prominent ridges over the eyes;
one step more along that path would bring us to the
gorilla or the chimpanzee. The array of lower pri-
mates, from the lemur to the gorilla, gives a series of
forms exhibiting a progressive advance in respect to
the size of the brain and cranium, and a gradual retreat
of the jaws to a position underneath the cranium ; and
one step further brings us to man. In a word, these
two lines join — in fact, they are directly continuous.
There is a far smaller difference between the lowest man

196 DOCTRINE OF EVOLUTION

and the highest ape than we have been accustomed
to suppose.

Thus in general terms, it can justly be said that
process of evolution which developed the first man from
its ape-man progenitor seems to have continued during
subsequent ages. Spreading out in diverging lines of
evolutionary descent no less clearly than they have in
geographical respects, certain races have far surpassed
their fellows of a lower order, which, like the brute
pygmy, remain nearer the common structural form from
which all men have sprung.

VI

THE MENTAL EVOLUTION OF MAN

The problems dealing with the make-up of the human
mind and with the evidences of mental evolution bring
the student to matters of more vivid human interest.
Mental phenomena are so complex and intricate that it
is well-nigh impossible to analyze their history without
a knowledge of the principles derived from the broad
study of evolution as a general doctrine, where human
prejudice is not so large a factor and w^here his perspec-
tive is less affected by the proximity of the observer to
his facts. For these and other reasons the foregoing
treatment of human evolution has been confined to the
purely structural characteristics of man as a species and
of human races as so many varieties of this type. When
the broad comparative methods of biological science are
employed for the elucidation of human anatomical
facts, the result in this special case, like that established
through the study of the characteristics of hving things
in general, is the proof that evolution gives the most
rational and natural explanation of the observed data.
This being true, the naturalist who turns from purely
structural matters to human intellect and its history,
finds well-tried methods of inquiry already available,

197

198 DOCTRINE OF EVOLUTION

and he approaches his further studies with a conviction
that evolution, having proved to be universal so far,
in all probability will be found equally true in the case
of psychological phenomena. This expectation is in-
deed realized, and the scope of the doctrine is extended
over a new field, when the facts of human psychology
are treated as materials for impersonal comparative
study ; and this result is not only useful and valuable
in and by itself, but it also provides in the principles
of mental evolution the transition to the field of social
relations and ethical ideas and ideals which are appar-
ently the unique possessions of men as individuals and
as associated groups.

The field of comparative psychology might seem at
first sight to be a foreign territory to the average well-
informed layman in science, but the contrary is really
the case. Every one has thought at one time or an-
other about his own mental make-up, and about the
minds of others. No one can watch a child at play
with his toys or at work with his schoolbooks without
being struck by many evidences of marked differences
between the immature and the experienced types of
mind. Every one knows also that the mental '^ scheme
of things " is by no means the same for all nations or
races of mankind existing to-day, while furthermore
the fact is entirely familiar that the intellectual heritage
of a present race has changed in the course of previous
ages. Therefore in this field as before we need only to
amplify our knowledge of such representative psycholog-
ical facts as these by drawing upon the full stores of
the special investigator, in order to learn that human
thought, like the human frame, has undergone a natural

MENTAL EVOLUTION OF MAN 199

history of transformation to become what it is and what
it was not.

Many who would be ready to accept the evolution of
physical characteristics find it impossible to treat the
history of human mentality as a subject for dispassion-
ate consideration, because above all else the intellectual
powers of mankind seem to be truly distinctive. It is
only after constant use of the methods of science that
we can bring ourselves to see how closely we resemble
lower forms in physical make-up ; still greater reluc-
tance must be overcome before we can view our mental
processes as counterparts of those of inferior animals,
so essential to our very humanity do they seem. But
our duty to undertake the task is plain, and its dis-
charge will be greatly facilitated by a clear realization
that mental evolution is but a part of human transfor-
mation in times past, as the latter is only a small frac-
tion of the universal process of organic evolution in
general. While our own nature and inquisitiveness
give us so intense an interest in the teachings of science
that relate to the constitution and history of human
faculty, wherefore these matters gain an undue promi-
nence in perspective, it must never be forgotten that
these teachings do not stand by themselves, for they are
built upon the sure foundations already laid in physical
evolution ; and these foundations cannot be disturbed
by our failure to use them as a basis when we construct
our own conceptions of human intellect and its history.

Before passing to the systematic review of the facts
and principles of comparative psychology which demon-

200 DOCTRINE OF EVOLUTION

strate evolution, there are certain general aspects of the
subject to be considered so as to clear the ground, as it
were, for further progress. When the several organic sys-
tems of the human body were compared with those of
the apes and of lower animals, their evolution was proved
as far as the purely physical and material character-
istics were concerned. But we know that there is no
part of any one of these systems which has not its own
particular function, even though this may be a rela-
tively passive one ; while furthermore, science does
not know of any physiological activity without some
organ or tissue or cell as its material basis. Therefore
the evolution of an organic system in material respects
involves its functional or dynamic evolution as an insep-
arable correlate ; the two proceed in unity, and they
cannot be regarded as entirely distinct without violat-
ing common-sense.

The fin of a fish is used as an organ of locomotion in
water ; from some such organ have evolved the walking
limbs of amphibia and reptiles, constructed for pro-
gression upon land. Among the mammalia the fore
limbs have become structurally adapted so as to be such
diverse organs of locomotion as the stilt-like leg of a
horse, the flipper of a seal, the whale's paddle, and the
bat's wing, while among the birds the wing may change
into a flipper like that of the penguin, or become reduced
to a vestige as in Apteryx. We may focus our attention
upon the material likenesses and differences in such a
series of locomotory organs, but an inevitable accom-
paniment of their physical changes in the transforma-
tion of species has been an evolution in the functional
matter of locomotion. The most complex and dif-

MENTAL EVOLUTION OF MAN 201

ferentiated digestive tracts of even the highest animals
have evolved from a simple sac like that of a polyp or
jellyfish, as we know from the independent testimony
of comparative anatomy and embryology ; in this case
also the evolution of alimentary functions is no less
inseparable from the transformations in structural
respects. And again, we cannot understand the his-
torical development of vision without taking into
account the eyes of various types belonging to lower
and higher animals.

So it is with the nervous systems of man and other
animals, and with their functions. The nervous system
of the human organism comprises identical organs with
the same arrangements that are found in other pri-
mates and in lower vertebrates as well ; the differences
in structure are differences in the degree of the com-
plexity of certain parts, notably of the cerebrum.
Therefore the evolution of human mentality, which
depends upon a human type of brain as a physical basis,
is already demonstrated with the proof that the human
brain and nervous system have evolved. It is true
that an invariable and necessary connection between
mind and matter is implied in the foregoing statement,
and this is something which demands further consider-
ation at a later point. But just how the human mind
is produced by or depends upon the brain, is of far less
importance for us at this time than the obvious fact
that mental performance requires active nervous tis-
sues. So far investigation has been unable to discover
a valid reason for a belief in the existence of mental
phenomena, as such, apart from some kind of material
basis. And while we may prefer to restrict the use of

202 DOCTRINE OF EVOLUTION

the word mind to the series of nervous processes going
on in the human organ of thought, in so far as these
processes are carried on by the peculiar tissues of the
nervous system they cannot be finally distinguished
from the functional products or accompaniments of the
same kind of active tissues and organs in lower crea-
tures. Thus the subject of mental evolution becomes
much clarified at the outset by understanding that
nervous processes and nervous systems evolve together.
In the direct treatment of the facts and principles
of mental evolution we can use exactly the same classi-
fication and subdivisions of the materials of study as
heretofore, because psychological data are the corre-
lates of material organic systems, and also because the
former, being natural phenomena, are subject to the
methods of analysis which can be employed for any
series of objects that have undergone evolution. Sepa-
rating the matter of fact from the question as to the
method, and recalling the main bodies of evidence as
to the reality of evolution, we may establish four sec-
tions of the subject before us : these are (1) the anatomy,
(2) the embryology, and (3) ^' palaeontology " of mind,
and (4) an inquiry into the way nature deals with the
psychical characteristics of organisms in accomplishing
their evolution. To specify more particularly, it is
possible in the first place* to compare the activities
belonging to the category of mental and nervous opera-
tions, displayed by man and other organisms, and the
results form the subject of comparative descriptive
psychology; the second division, namely, develop-
mental or genetic psychology, deals with the sequence
of events in the life of a single individual by which the

MENTAL EVOLUTION OF MAN 203

infantile and adolescent types of mind become adult
intellectuality ; in the third place, in speaking of the
palaeontology of mind, the phrase is used to refer to the
varied and changing mental abilities of human races in
historic and prehistoric times as they may be demon-
strated and determined by the evidences of the culture
of such earlier epochs. In considering the matter of
method, the questions are whether variation, inheritance,
and selection are as real in the world of mental phe-
nomena as they are in the material world, and whether
the laws are the same or similar in the two cases. We
shall learn how the results of such studies prove with
convincing clearness, first, that the contents of the indi-
vidual mind and of the minds of various human races
are truly the products of natural evolution, and second,
that the human mind differs only in degree from that
of lower organisms, and not in kind or fundamental
nature.

When the operations of human mental life are ex-
amined, they include what are called processes of
reason as apparently distinctive elements. The lower
mammalia exhibit a simpler order of '' mentality " de-
noted intelligence, while the nervous processes of still
simpler forms are called instinctive and reflex activities.
These are the terms of the comparative array of psy-
chology which are to be separately examined and classi-
fied, and to be brought into an evolutionary sequence
if common-sense directs us to do so.

Let us begin our comparative study with an example
of the simplest animals that consist of only a single cell,

204 DOCTRINE OF EVOLUTION

such as the httle protozoon Amoeba, We have become
famiUar with this organism as one that carries on all of
the vital functions within the limits of a single struc-
tural unit ; it is a mass of protoplasm enclosing a nu-
cleus, and as a biological individual it must perform all
of the eight tasks that are essential for life. It does
not possess a digestive tract, but it does digest ; it does
not have breathing organs, but it does respire ; and it
is particularly noteworthy that it must coordinate the
different activities of its parts, and maintain definite
relations with the environment, even though its coor-
dination and sensation are not accomplished by any
special parts that would deserve the name of elementary
nervous organs. Its many activities are simple re-
sponses to stimuli that reach it from without, and its
reactions to such stimuli are called reflex processes.
Should the light become too strong, it will slowly crawl
to a shady place ; should the water in which it lives
become warmer, it responds by displaying greater
activity. It exhibits, in a word, the property of irri-
tability, — that is, simply the power of receiving and
reacting to stimuli ; and being only a single cell this
property is held in common by all of its parts.

We come next to a simple many-celled animal like
the polyp Hydra, or a jellyfish. In such an animal
the body is composed of numerous cells which are not
all alike either in their make-up or in their functions.
Some of them are concerned primarily with digestion,
others with protection, while still others are exempt
from these tasks and as sense-cells they devote all their
energies to the reception of stimuli from without, or,
beneath the outer sheet of cells of the two-layered body,

MENTAL EVOLUTION OF MAN 205

they conduct impulses from one part of the animal
to another, and thus serve as coordinating members of
the community. For the first time, then, a nervous
system as such is set apart and speciahzed to devote
itself to the two tasks of sensation and coordination
that are performed by nervous systems throughout the /
entire range of organisms higher in the scale. But the
activities of Hydra, like those of Amoeba, are reflex
and mechanical, — that is to say, given similar stimuli
and similar physiological states of the animal, the reac-
tions will be the same. A little water-crustacean like
Daphnia may swim against the tentacles of Hydra;
it is stung to death by the minute cell-batteries which
the animal possesses, and then in a mechanical way
the tentacles transport the food to the mouth, through
which it is passed inward to the digestive cavity.
There is nothing that can be called '' mentality "
throughout these processes, but the series of activities
is much more complex than in Amoeba because the
whole organism is constructed more elaborately, and
because the special and peculiar mechanism directing
the activities has advanced to a far higher condition.

Passing to the jointed animals like worms and in-
sects, we find nervous mechanisms that are still more
intricate, and with their advance in structural respects
there is a corresponding and correlated progress in
their functions. Because the whole organism has de-
veloped more highly differentiated groups of organs
to perform the several biological tasks, such as eating
and respiring and moving, it is necessary for the nervous
structures concerned with the direction of these actions
to become more efficient. An earthworm avoids the

206 DOCTRINE OF EVOLUTION

light of day and digs its burrow and seeks its food by
wonderfully coordinated activities of its muscles and
other parts, which are controlled by a double chain of
ganglia along its ventral side, connected with a similar
pair of grouped nerve-cells above the anterior part of
the digestive tract. The ganglia of each segment
exercise immediate supervision over the structures of
their respective territory, while they pass on impulses
to other ganglia so that movements involving many
segments can be properly adjusted. Everything an
earthworm does is controlled by the cells grouped in
these ganglia, or scattered along the intervening con-
necting cords. We speak of its acts as instinctive,
employing a term which seems to indicate a different
kind of operation carried on by the nervous system,
but a moment's thought will show that an instinctive
act is simply a complex group of reflex acts. The
physical basis and ultimate unit is a cell, and the func-
tional unit is likewise a cell act ; therefore the seeming
difference proves to be one merely of degree and not of
kind. The greater complexity of the worm's nervous
system as compared with that of Hydra gives to the
whole mechanism a plasticity that diverts the attention
from the mechanical nature of the entire instinctive
act and of its basic cell elements.

The instinct, like the elementary reflex, is determined
by heredity. Because a certain configuration of the
cells and fibers making up a nervous system is inherited
as well as the characters of the constituent elements
themselves, a worm or an insect is enabled to act as it
does. A butterfly does not have to learn how to fly,
for it flies instinctively. When it emerges from its

MENTAL EVOLUTION OF MAN 207

chrysalis with its complete adult series of wings and
muscles, it has also the nervous mechanism by which
these parts are mechanically controlled. A ground-
wasp deposits its eggs in a small burrow in which it
places also a caterpillar or a grasshopper paralyzed by
stinging, so that when the larva is hatched from an egg
it finds an ample supply of fresh food provided by a
complex series of its mother's acts that seem to be
directed by conscious maternal solicitude. When the
larva passes through the later stages of development
and makes its way to the open air as a fully formed
adult, it in its turn may go through the same course of
action as its parent, but it is clear that it cannot have
any remembrance of its mother's work or any personal
knowledge of the value of burying its own eggs in a
chamber with a living prisoner to serve as food. It
was an egg when its parent did these things ; as a parent
itself it does not remain on watch to see how beneficial
or fruitless its acts may be. A mechanism produced
by nature's methods, the ground-wasp behaves as it is
capable of working with its inherited structure and its
inherited instinctive powers of coordination and sensa-
tion.

The complex lives of communal insects like ants and
bees bring us to the level of mentality where an under-
standing of causes and effects seems to be the guide
for conduct. Nevertheless the facts do not warrant
the assumption that reason and intelligence play any
part in the mental life of these creatures, as they do in
the lives of man and the apes. Because we ourselves
can see the utility of the definite and peculiar behavior
of the queen and the worker, there is no logical necessity

(

208 DOCTRINE OF EVOLUTION

for assuming an identical form of knowledge as a pos-
session of these insects. Many investigators have
dealt with these fascinating subjects, and they are al-
most unanimous in the conclusion that the instinct
of an insect is a mechanical and hereditary synthesis
of combined reflex acts.

The lower orders of psychological processes play a far
larger part in the lives of the higher animals than we are
wont to believe. A pointer and sheep dog possess
different qualifications in the way of instincts that
make them useful to man in different ways. A bull-
dog or a game-cock does not reason out its course of
action during a contest, but like a mechanism when
the spring is released, it acts promptly and with effect.
A ball flashing past the human eye causes the lids to
close unconsciously, and it is not always possible to
inhibit this instinctive mechanical act by the exercise
of the will. An examination of the workings of the
human body reveals manifold activities of an even lower
or reflex nature, like the movements of the viscera and
the adjustments in respect to the amount of supplies
of blood sent to different parts of the body as local
needs arise. Directed always by specific portions of
the nervous system, such reflex actions play their part
in human life without any effort on the part of reason
and so-called will, and without coming into conscious-
ness except indirectly and subsequently.

Passing by many interesting members of the psy-
chological series of intergrading forms, we reach the
familiar animals like the cat and dog and horse which
display what is called intelligence. This is the power
to learn by experience, and to improve the quality and

MENTAL EVOLUTION OF MAN 209

promptitude of reactions to stimuli. In certain re-
spects intelligence seems to differ from instinct, inas-
much as it involves a response to stimuli that may
be altered and quickened by repeated experience, but
in ultimate analysis the two forms of psychological
processes are fundamentally alike. A single example
chosen from Thorndike's extensive investigation will
serve to bring out the primary characteristics of intelli-
gence. A cat was placed in a latticed cage provided
with a door that could be opened from within when a
catch was pressed down, and meat was put in a dish
outside the door where the cat could see it. At first,
the animal escaped from the cage by freeing the door
during its aimless scrambling about the catch, but as
trial after trial was made, the time necessary for the
cat to make its way out was shortened, until after
seventy-five or one hundred trials, the animal imme-
diately opened the door and seized the food. In me-
chanical terms, the connection between " scrambling
about the door " and " freedom to get the meat " be-
came established by numerous repetitions until the
originally disconnected elements were physiologically
associated and made inseparable. When animals like
horses and seals and dogs are trained for the circus, it is
by exactly the same method, for training consists merely X
in the establishment of a psychological sequence so thatV
the performance of one series of acts leads mechanically
to others. Thus we learn that the psychological prop-
erty called intelligence is the ability to establish wide
relations between numerous activities which are them-
selves of a more or less complex nature ; and we find
also that because these elements are ultimately nerve- *

210 DOCTRINE OF EVOLUTION

cell and sense-cell reflexes, an intelligent response is
quite as machine-like as any and all of its elements. A
difference in degree of complexity and extent is the only
thing that places intelligence apart from instinct and
reflex action, for the units are the same in all cases, —
so far as science knows.
\ The apes are of the greatest value in providing the
transition from the grade of intelligence to the human
level where reason is found. Whether or not a chim-
panzee can reason at all is less important than the fact
that its total ''mental" powers are lower than those
of man, and higher than those of inferior mammalia.
Apes are far more susceptible to training than cats and
dogs, because their improved nervous mechanism en-
ables them to establish a psychological sequence with
greater facility. If we are to judge by the facts at hand,
these creatures possess a low order of mentality, like,
but by no means equivalent to, that of man.

At the end of the comparative scale, we reach the
human mind which is characterized by its ability to
perceive and recognize far wider relations than those
which are involved in intelligence. Human conscious-
ness is the stream of thoughts and feelings which con-
stitute the immediate contents of mind. In our own
case, we know both the activities we perform and some
of the internal phenomena with which such activities
are connected. Then we are impelled to compare the
objective phenomena of action with the behavior of
other men and of lower organisms, and if their behavior
does not coincide with our own we are justified in believ-
ing that its direction lacks some of the elements we know
about in our own case. This is the method of compar-

MENTAL EVOLUTION OF MAN 211

ative psychology, which estabhshes the conclusion that
reason is the more complex term of a series to which
reflex action, instinct, and intelligence directly lead.

Were we to study in detail the psychology of adult
human beings, we would find only more truly that
instinct and intelligence play a large part in our every-
day mental life, and more certainly that even the high-
est reasoning powers we possess are only more complex
in nature than the nervous processes of lower mammals
and invertebrates. Just as the nervous systems ad-
vance in physical or structural respects, so must their
activities become more and more complex until the
result is human faculty.

We must now briefly consider what may be called
the '' comparative anthropology " of mind which deals
with the various degrees of mental ability displayed by
different human races; this subject follows inevitably
upon the comparison of the human mind viewed as a
single type with the psychological processes of lower
animals. When we reviewed the diverse characteristics
of human races — the protrusion of the jaws, greater
or lesser stature, and the like — it appeared that so-
called " lower " races could be distinguished which
differed from the '^ higher " races in the direction of the
apes ; the question immediately arises whether similar
distinctions and relations are discoverable on the basis
of mental traits. But in the present case there are not
so many well-substantiated differentia at the disposal
of the student, and it does not appear so clearly that
the " higher " races are furthest from the lower pri-

212 DOCTRINE OF EVOLUTION

mates and lower mammalia as regards their mental pro-
cesses. What facts there are, however, prove to be
highly significant, and they materially amplify our
conception of human faculty as a product of evolution.
The essential point is that the intellectual attain-
ments of various races are by no means the same. The
calculus is a mental product of the white race only;
gunpowder and printing from movable type were
independently invented by the Caucasian and Mon-
golian races ; but the American Indian and the Negro
never originated them. Human faculty, to employ
the most general term for all that distinguishes man
from the brutes, proves to be a very varied thing when
we draw comparisons between and among races with
independent lines of ancestry and heredity occupying
widely separated areas. Should we analyze it, we find
it to be composed of three constituents ; namely, the
physical elements of the brain, the degree to which the
observational or perceptual and higher elements co-
operate in building up the conceptions peculiar to the
type, and the materials with which the physical mechan-
ism deals, in the way of environmental, educational, and
social ^' grist for the mental mill." Many anthropolo-
gists accord too great an importance to the third con-
stituent of human faculty, I believe, and they are
therefore led to deny that races differ in mental respects
to so large a degree as the thoroughgoing evolutionist
would contend. They hold that differences in such
things as powers of observation are due to training:
that, for example, an American Indian or a South Sea
Islander sees certain things in his environment more
quickly than a white man only because these are the

MENTAL EVOLUTION OF MAN 213

things which the experiences of his earher Hfe have
accustomed him to look for and to find. This may be
granted, and it may also be admitted that children of
so-called " lower " races can be educated side by side
with the youth of white races without noticeably falling
behind, up to a certain point when, at the age of adoles-
cence, in the classic case of the Australian natives,
other factors prove to be obstacles to further progress.
We must also recognize that the character of the en-
vironment of a race determines to a large extent the
mode of life of the people ; a forest-dwelling Indian of
the interior is a hunter as well as a warrior, while a
South Sea Islander is a navigator and a fisherman.

But the fact remains that the inhabitants of similar
countries have reached markedly different grades of
intellectual and cultural life. Anglo-Saxon dominance
must be referred ultimately to Anglo-Saxon heredity
and not to the peculiarities of the land. Although
adaptation is no less necessary for men as individuals
and as social groups than it is for all other living things,
I believe that it is to diversity in constitutional endow-
vjments, however these may have arisen, that we must
attribute the superiority of some races over others.
The question is not whether a savage race can or cannot
adopt the higher conceptions of a civilized people ;
the fact is that they have not actually become civilized
by themselves. Thus, while evolution in mental re-
spects has not resulted in the loss of plasticity in the
case of the brain and the nervous system as a whole,
wherefore the activities of these organs still remain
capable of individual and racial modifications that are
impossible in the case of the skeleton and in the color

214 DOCTRINE OF EVOLUTION

and shape of the eye, it remains true that races do differ
intellectually, and that their differences are marks of
a mental evolution quite as definite as their physical
natural histories of change.

In my own view the strongest and most impressive
evidence bearing upon the great problem before us is
provided by the series of transformations by which the
human intellect develops during an individual life.
Mind has an embryology no less significant than that
of the skull or of any other element of the body; and
its investigation leads to the evolutionary interpreta-
tion quite as surely as the study of the various grades
of adult psychology constituting the anatomical se-
quence, which we have reviewed previously. When in
the earlier part of the book we dealt with embryology
in general, we learned how the changes which take place
when an organism develops from an egg demonstrate
the actuality of true organic transformation without
the necessity of concluding or inferring that this process
might occur. It is not superfluous to insist again that
the essential fact in evolution is the alteration of one
organic characteristic into another type ; must we not
recognize at the very outset that mental transformation
is as real as physical development ?

In the first instance we might concern ourselves with
the physical basis of mind and its history. In the
earliest stages of human embryology no nervous system
whatsoever is present, and it is unreasonable to suppose
that there is anything going on which corresponds to
human thought. A little later a cellular tube is estab-

MENTAL EVOLUTION OF MAN 215

lished as a primitive nerve axis, which at first is nearly
uniform throughout its entire length and displays no
differentiation into brain and spinal cord. Before long
an enlargement of the anterior end expands and de-
velops into a primitive three-parted brain. It is not
yet a real brain, however, and it is entirely incapable
of functioning in such a way as to justify the use of the
word mental for the results of its operations. We know
that it is only in the cerebral hemisphere of the adult
brain that the processes of true human consciousness
go on. But it is not until long after the three-parted
stage that the cerebral hemispheres make their appear-
ance; therefore we cannot speak of mind as present
when the cell and tissue basis of mind is not present.
When, now, the cerebral hemispheres do appear, they
are small bean-shaped structures no larger relatively
than those of a fish. Later they enlarge so as to attain
the relative size of the cerebral hemispheres of an
amphibian, and still later they are like those of a
reptilian brain. Continuing to enlarge, they begin to
fold so that the total surface is increased without very
much addition to their bulk. At this time the cerebral
hemispheres of the brain of the human embryo are like
those of an adult cat or dog. The process of general
enlargement and of progressive convolution are con-
tinued, and stages are reached and passed which corre-
spond with the monkey and ape conditions.

Nothing in human development is more impressive
than the origin of the cerebrum and its development
by passing through successive stages which are counter-
parts in the main of the adult brains of other and lower
animals. The alteration of a tissue-mechanism con-

\

;

216 DOCTRINE OF EVOLUTION

structed in one way into a tissue-mechanism of a more
complex nature, provides the most conclusive evidence
of the reahty of brain evolution, because the process of
transformation actually takes place.

But in the present connection we are more interested
in the dynamic or functional aspects of mental evolu-
tion, which it must be remembered are inseparably
bound up with the physical structures and their modi-
fications. After a human infant is born its activities
are reflex and mechanical like those of the adult mem-
bers of lower groups. As it grows it performs instinc-
tive acts because its inherited nervous system operates
in the purely mechanical manner of a lower mammal's
nervous system. For th'ese reasons an eminent psy-
chologist has said that the mental ability of an infant
six months old is about that of a well-bred fox terrier.
The same infant at nine months displays an intelligence
of a higher order equal to that of a well-trained chim-
panzee ; it has become what it was not, and in so far
it has truly evolved in mental respects. At two years
of age the child is incapable of solving problems of the
calculus, for its reasoning powers are elementary and
restricted, but these same powers change and intensify
so as to render the older mind quite capable of grasping
the highest of human conceptions and ideas. In my
judgment the unbroken transformation of a child's
mind that exhibits only instinct and intelligence into
an adult's mind with its power of reasoning, is far more
conclusive as proof of mental evolution than the infer-
ence drawn from the comparisons we have made above
of the adult psychological phenomena of man, ape, cat,
and fish. It is surely natural for such mental trans-

MENTAL EVOLUTION OF MAN 217

formations to take place, for they do take place in the
vast majority of human beings ; when they do not,
in cases where the brain fails to mature, we speak of
unnatural or diseased minds.

The third division of our evidence relating to mental
evolution constitutes what we have called the palaeon-
tology of mind. By this term we mean the study of
human minds of the past as we may know them through
the many varied relics and documents which indicate
their characters. It is only too obvious to every one
that human knowledge has advanced in the course
of time and that every department of human thought
and mental activity has participated in this progress.
No one would have the temerity to assert that we know
nothing more than our ancestors of 5000 or even 1000
years ago. Our common-sense teaches us even before
the man of science produces the full body of evidence
at his disposal that human faculties have evolved.
With regard to reasoning powers, which form one of the
four distinguishing characteristics of the human species
as contrasted with other animals, the case has already
been reviewed, and we now turn to speech and language
and other departments of human mentality. When
we compare the attainments of present day men with
the abilities and ideas of their ancestors we will do for
mental phenomena precisely what was done when we
compared the skeletons of modern animals with those
of creatures belonging to bygone geological ages ; in
this reason is found the justification for the phrase
employed in the present connection.

218 DOCTRINE OF EVOLUTION

Written history furnishes a wealth of material for
interpreting the mental conditions of ancient peoples,
but beside documentary evidence the anthropologist
learns to use inscriptions of prehistoric times, the primi-
tive graphic representations on tombs and monuments,
and even the characteristics of crude implements like
axes and arrow-heads. The layman finds it difficult
at first to regard such relics as indications of the mental
stature of the people who made and possessed them;
but a little thought will show that a man who used a
rough stone ax in the time of the ancient Celts could
not possibly have had a mind which included the con-
ception of a finished iron tool or modern mechanism.
So in all departments of human culture, the evolution
of material objects may be justly employed in inter-
preting and estimating the mental abilities of ancient
peoples.

r

La^iguage is undoubtedly the most important single ]

intelleclyual possession of mankind, for it constitutes, *

as it were, the very framework of social organization. i

Without a ready means of communication the myriad !

human units who perform the varied tasks necessary j

for the economic well-being of a body-politic would I

be unable to coordinate their manifold activities with i

success, and the structure of civilized societies at least *

would collapse. It needs no legend of a Tower of Babel -^
to make this plain. So fundamental is this truth that

although we may not have recognized it explicitly, we j
unconsciously form the belief that speech and language
are exclusive properties of the human species, and even

MENTAL EVOLUTION OF MAN 219

more characteristic of man alone than the power of
reason itself. While organized language is clearly '
something that as such we do not share with the lower
animals, nevertheless we cannot regard the communi-
cation of ideas or states of feeling by sound as an exclu-
sive property of mankind. All are famihar with the
difference between the whine and the bark of a dog j,
and with the widely different feehngs that are ex-
pressed by these contrasted sounds. And we know too
that dogs can understand what many of their master's
words signify, as when a shepherd gives directions to
his collie. We could even go further down in the scale
and find in the shrill chirping of the katydid at the
mating season a still more elementary combination of
significant instinctive sound elements. To the com-
parative student the speech of man differs from these
lower modes of communication only in its greater com-
plexity, and in its employment of more numerous and
varied sounds, — in a word, only in the higher degree
of its evolution. And it is even more evident that the
diverse forms of speech employed by various races
have gradually grown to be what they now are.

At the outset it is well to distinguish between writ-
ing, as the conventional mode of symbolizing words,
and spoken language itself; the two have been more ]^
independent in their evolution than we may be wont
to believe. Speech came first in historical develop-
ment, just as a child now learns to talk before it can
understand and use printed or written letters. Further-
more, many races still exist who have a well-developed
form of language without any concrete way of record-
ing it. It is true, of course, that back of the conven-

220 DOCTRINE OF EVOLUTION

tions of speech and writing are the ideas themselves
that find expression in the one way or the other, or
even by the still more primitive use of signs and ges-
tures. But it is not with these ultimate elements of
thought that we are now concerned; our task is to
learn, first, what evidences are discoverable which show
that the property of human language in general has
originated by evolution, and then, in the second place,
to perceive how this development proves an evolution
of one group of ultimate ideas, namely, human concepts
of the modal value of words and symbols as expressions
of ideas themselves.

A simple common-sense treatment of obvious facts
will greatly facilitate our progress. We know very well
that the English we speak to-day differs in many ways
from the language of Elizabethan times, and that the
former is a direct descendant of the other. The latter,
in turn, was a product of Norman French and Anglo-
Saxon, — a combination of certain elements of both,
but identical with neither of its immediate parents.
The Saxon tongue itself has a history that leads back
to King Alfred's time and earlier. Thus we are already
aware of the fact that our speech has truly evolved,
like the physical structure of the men who employ it ;
and we know, too, how readily new words are adopted
into current English, like tahu from Polynesia, or garage
from the French, showing that language is even now
in process of evolution.

The sounds that make up spoken words can be
resolved into a single element with its modifications;
this basic element is the brute-like call or shout made
with the mouth and throat opened wide — a sound we

MENTAL EVOLUTION OF MAN 221

may have heard uttered by men under the stress of
pain or terror. All of the various vowels are simply
modifications of this element by altering the shape of
the mouth cavity and orifice, while the consonants are
produced by interrupting the sound-waves with the
palate or lips or tongue. Like the cell as a unit of
structure throughout the organic world, this elemental
utterance proves to be the basic unit of all human
languages, which vary so widely among races of to-day
no less than they have in the history of any single
people.

One of the first steps in the making of spoken words
was taken by human beings when they imitated the
calls or other sounds produced by living things, and
tacitly agreed to recognize the imitation as a symbol
of the creature making it. Thus the names for the
cuckoo and the crow in many languages besides our
own are simply copies of the calls uttered by these
birds; a Tahitian calls a cat mimi; the name for a
snake almost invariably includes the hissing attributed
to that creature. After a time words which were at
first simply imitations and which referred only to the
things that made these sounds came to refer to certain
qualities of the things imitated, so that the naming of
other than natural objects, such as qualities, began,
leading ultimately to the use of words for qualities
belonging to many and different objects in the way of
abstractions.

Much light upon the evolution of language is ob-
tained when we treat the speech of various races as
we did the skeletal structures of cats and seals and
whales. When we compare the Italian, Spanish, Por-

222 DOCTRINE OF EVOLUTION

tuguese, and French languages, they reveal the same
general structure in thousands of their words, — a
common basis which in these cases is due to their
derivation from the same ancestor, the Latin tongue.
The Latin word for star is stella, and the Italian word
of to-day is an identical and unchanged descendant,
like a persistent type of shark which lives now in prac-
tically the same form as did its ancestor in the coal
ages. The Spanish word is estrella, a modified deriva-
tive, but still one that bears in its structure the marks
of its Latin origin; the French word etoile is a still
more altered product of word evolution. Even in the
German stern, Norse stjern, Danish starriy and English
star we may recognize mutual affinities and common
ancestral structure. Choosing illustrations from a dif-
ferent group, the Hebrew salutation ''Peace be with
you," Shalom lachem, proves to be a blood cousin of
the Arabic Salaam alaikum, indicating the common
ancestry of these diverse languages. Among Polynesian
peoples the Tahitian calls a house a fare, the Maori of
New Zealand uses whare, while the Hawaiian employs
the word hale, and the Samoan, fale. Whenever we
classify and compare human languages, we find similar
consistent anatomical evidences of their relationships
and evolution. We can even discern counterparts of
the vestigial structures like the rudimentary limbs of
whales. In the English word night certain letters do
not function vocally, though in the German counterpart
Nacht their correspondents still play a part. In the
word dough as correctly pronounced the final letters
are similarly vestigial, although in the phonetic relative
tough they are still sounded.

MENTAL EVOLUTION OF MAN 223

The evolution of the art of writing appears with
equal clearness when we compare the texts of modern
peoples with inscriptions found on ancient temples and
monuments and tablets. Even races of the present
day employ methods of communicating ideas by writ-
ing symbols that are counterparts of the earliest stages
in the historic development of writing. An Eskimo
describes the events of a journey by a series of little
pictures representing himself in the act of doing vari-
ous things. A simple outline of a man with one arm
pointing to the body and the other pointing away in-
dicates ^^I go.'' A circle denotes the island to which
he goes. He sleeps there one night, and he tells this
by drawing a figure with one hand over the eyes, in-
dicating sleep, while the other hand has one finger
upraised to specify a single night. The next day he
goes further and he employs the first figure again. A
second island is indicated, in this case with a dot in the
center of the circle to show a house in which he sleeps
two nights, as his figure with closed eyes and two
fingers uplifted shows. He hunts the walrus, an out-
line of which is given alongside of his figure waving a
spear in one hand ; likewise he hunts with a bow and
arrow, which is demonstrated by the same method. A
rude drawing representing a boat with two upright
lines for himself and another man with paddles in their
hands gives a further account of his journey, and the
final figure is the circle denoting the original island to
which he returns.

Pictography, as this method of communicating ideas
is called, is often highly developed among the Ameri-
can Indians. For example, a petition from a tribe of

224 DOCTRINE OF EVOLUTION

Chippewa Indians to the President of the United States
asking for the possession of certain lakes near their
reservation is a series of pictures of the sacred animals
or 'Hotems" which represent the several subtribes.
Lines run from the hearts of the totem animals to the
heart of the chief totem, while similar lines run from
the eyes of the subsidiary totems to the eyes of the
chief, and these indicate that all of the subtribes feel
the same way about the matter and view it alike, —
the sentiment is unanimous. From the chief totem
run out two lines, one going to the picture of the desired
object, while the other goes to the President, conveying
the petition. Thus pictography, a method of writing
that belongs to the childhood of races, may be made
to communicate ideas of a strikingly complex nature.

The ancient and modern inscriptions of Asia, from
the Red Sea to China, present many significant stages
in the development of picture-writing. In earliest ages
the men of Asia made actual drawings of particular
objects, such as the sun, trees, and human figures;
subsequently these became conventionalized to a cer-
tain degree, but even as late as 3000 b.c. the Akkadian
script was still largely pictographic. From it origi-
nated the knife-point writing of Babylonian and Chal-
dean clay tablets, while among the peoples of Eastern
Asia, who continued to draw their symbols, the tran-
sition to conventionalized pictures such as those made
by the Chinaman was slower and less drastic.

In another line of evolution, the hieroglyphics of
Egyptian tombs and monuments illustrate a most
interesting intermediate condition of development.
These inscriptions have been deciphered only since the

MENTAL EVOLUTION OF MAN 225

discovery of the famous Rosetta stone-fragment, which
bears portions of three identical texts written in hiero-
glyphics, in Greek, and in another series of symbols.
The Egyptian used more or less formalized characters
to represent certain sounds, while in addition to the
group of such characters combined to make a word, the
scribe drew a supplementary picture of the thing or
act signified. For instance, xeftu means enemies, but
the Egyptian graver added a picture of a kneeling bow-
man to avoid any possible misapprehension as to his
meaning. The symbols denoting 'Ho walk" are fol-
lowed by a pair of legs ; the setting sun is described
not only by a word but also by its outline as it lies on
the horizon. Here again one is struck by the simi-
larity between a stage in the historic development of
racial characteristics and a method employed at the
present time to teach the immature minds of children
that certain letters represent a particular object; in a
kindergarten primer the sentence ''see the rat and the
cat " is accompanied by pictures of the animals specified,
in true hieroglyphic simplicity.

Just as the child's mind develops so that the aid of
the picture can be dispensed with, and the symbolic
characters can be used in increasingly complex ways,
in like manner the minds of men living in successive
centuries have evolved. While an evolution of human
conceptual processes in general is not necessarily im-
plied by the evolution of the forms of written language,
the former process is in part demonstrated by the latter
in so far as the change from the writing of pictures to
the use of conventional symbols involves an advance
in human ideas of the interpretation and value of the

Q

226 DOCTRINE OF EVOLUTION

symbols in question. A man of ancient times drew a
tree to represent his conception of this object; in the
writing of EngUsh we now use four letters to stand for
the same object, and none of these symbols is in any
way a replica of the tree. It is certainly obvious that
some change in the mental association of symbol and
object has been brought about, and to this extent there
has been mental evolution.

Passing now to other departments of human culture,
we must deal in the next place with the basic ^^arts of
life''; that is, the modes of conducting the necessary
activities of every day. All men of all times, be they
civilized or savage, are impelled like the brutes by their
biological nature to seek food and to repel their foes.
The rough stone club and ax were fashioned by the
first savage men, when diminishing physical prowess
placed them at a disadvantage in the competition with
stronger animals. Smoother and more efficient weapons
were made by the hordes of their more advanced de-
scendants, some of whom remained in the mental and
cultural condition of the stone age like the Fuegian,
until the white travelers of recent centuries brought
them newer ideas and implements. In Europe and
elsewhere the period of stone gave place to the bronze
and iron ages, and throughout the changing years
human inventiveness improved the missile and weapon
to become the bow and arrow of medieval civilization
and recent African savagery. The artillery and shells
of modern warfare are their still more highly evolved
descendants.

MENTAL EVOLUTION OF MAN 227

So it is with the dweUings of men, and the significance
of the changes displayed by such things. The cave
was a natural shelter for primitive man as well as for
the wolf, and it is still used by men to-day. Where it
did not exist, a leafy screen of branches served in its
stead ; even now there are human beings, like the
African pygmy and the Indian of Brazil, who are little
beyond the orang-outang as regards the character of
the shelter they construct out of vegetation. From
such crude beginnings, on a par with the lairs and
nests of lower animals, have evolved the grass huts of
the Zulu, the bamboo dwelHng of the Malay, the igloo
of the Arctic tribes, and the mud house of the desert
Indians. The modern palace and apartment are
merely more complex and more elaborate in material
and architectural plan, when compared with their primi-
tive antecedents.

Baskets, clay vessels, and other household articles
testify in the same way to an evolution of the mental
views of the people making them. The means of trans-
portation are even more demonstrative. The wagon
of the early Briton was like a rough ox-cart of the
present day, evolved from the simple sledge as a begin-
ning. In its turn it has served as a prototype for all
the conveyances on wheels such as the stage-coach and
the modern Pullman. The history of locomotives,
employed in the first chapter to develop a clear con-
ception of what evolution means, takes its place here
as a demonstration of the way human ideas about
traction have themselves evolved so as to render the
construction of such mechanisms possible.

The primitive savage swimming in the sea found

228 DOCTRINE OF EVOLUTION

that a floating log supported his weight as he rested
from his efforts. By the strokes of his arms or of a
club in his hand, he could propel this log in a desired
direction ; thus the dugout canoe arose, to be steadied
by the outrigger as the savage enlarged his experience.
A cloth held aloft aided his progress down or across
the wind, and it became an integral element of the
sailing craft, which evolved through the stages of the
galley and caravel to the schooner and frigate of
modern times. When the steam-engine was invented
and incorporated in the boat, a new line of evolution
was initiated, leading from the '' Clermont '^ to the
" Lusitania " and the battleship.

The history of clothing begins with the employment
of an animal's hide or a branch of leaves to protect the
body from the sun's heat or the cold winds. Other
early beginnings of the more elaborate decorative
clothing are discerned by anthropologists in the scars
made upon the arms and breast as in the case of the
Australian black man, and in the figured patterns of
tattooing, so remarkably developed by the natives in
the islands of the South Pacific Ocean. A visit to a
gallery of ancient and medieval paintings clearly shows
that the conventional modes of clothing the human
body have changed from century to century, while
it is equally plain that they alter even from year to
year of the present time, according to the vagaries of
fashion.

A brief review of the ''arts of pleasure,'^ including ^
music and sculpture and painting, demonstrates their

MENTAL EVOLUTION OF MAN 229

evolution also. The earliest cavemen of Europe left
crude drawings of reindeer and bears and wild oxen
scratched upon bits of ivory or upon the stone walls of
their shelters ; the painting and sculpture of early his-
toric Europe were more advanced, but they were far
from being what Greece and Rome produced in later
centuries. Indeed, the evolution of Greek sculpture
carried this higher art to a point that is generally con-
ceded to be far beyond that attained by even our
modern sculptors, just as flying reptiles of the Chalk
Age developed wings and learned to fly long before
birds and bats came into existence.

In the field of music, the earliest stages can be sur-
mised only by a study of the actual songs and instru-
ments of primitive peoples now living in wild places.
No doubt the song began as a recitation by a savage
of the events of a battle or a journey in which he had
participated. In giving such a description he lives
his battles again, and his simulated moods and pas-
sions alter his voice so that the spoken history becomes
a chant. From this to the choral and oratorio is not
very far.

Musical instruments seem to have had a multiple
origin. The ram's horn of the early Briton and the
perforated conch-shell of the South Sea Islander are
natural trumpets ; when they were copied in brass and
other metals they evolved rapidly to become the varied
wind instruments typified to-day by the cornet and
the tuba. In the same way the reed of the Greek
shepherd is the ancestor of the flute and clarionet.
Stringed instruments like the guitar, zither, and violin
form another class which begins with the bow and its

230 DOCTRINE OF EVOLUTION

twanging string. The power of the note was intensified
by holding a gourd against the bow to serve as a reso-
nance-chamber. When the musician of early times
enlarged this chamber, moved it to the end of the
bow, and multiplied the strings, he constructed the
cithara of antiquity, — the ancestor of a host of modern
types, from the harp to the bass-viol and mandolin.

The dance and the drama find their beginnings in
the simple reenactment of an actual series of events.
Among Polynesians of to-day the dances still retain the
rhythmic beat of the war-tread measure, and many of
the motions of the arms are more or less conventional-
ized imitations of the act of striking with a club, or
hurling a spear_, and other acts. To such elements
many other things have been added, but the fact re-
mains that our own formal dances, as well as the sun-
dance of the Indian and the mad whirl of the Dervish,
are modern products which have truly evolved.

When we turn to science and philosophy and other
intellectual attainments of modern civihzed peoples, it
is easier to see how evolution has been accomplished,
because we possess a wealth of written literature which
explains the way that human ideas have changed from
century to century. In these cases there can be no
question that such evidences provide accurate instru-
ments for estimating the mental abilities of the writers
who produced them. We shall take up the higher
conceptions of mankind at a later juncture, so at this
point we need only to note that even these mental
possessions, like household culture and even the phys-

MENTAL EVOLUTION OF MAN 231

ical structures of a human body, have changed and
differentiated to become the widely different interpre-
tations of the world and supernature that are held by
the civilized, barbarous, and savage races of to-day.
As we look back over the facts that have been cited,
and as we contemplate the large departments of knowl-
edge about human psychology, mental development,
and racial culture which these few details illustrate, we
come to realize how securely founded is the doctrine
that even the human mind with all its varied powers
has grown to be what it is. Indeed, it is solely due to
his mental prowess that man has attained a position
above that of any lower animal. And yet every hu-
man organ and its function can be traced to something
in the lower world ; it is a difference only in degree
and not in category that science discovers. The line
connecting civilized man with the savage leads in-
evitably through the ape to the lower mammalia pos-
sessing intelligence, and on down to the reflex organic
mechanisms which end with the Amoeba. It is a long
distance from the mechanical activities of the proto-
zoon to the processes of human thought ; yet the phys-
ical basis of the latter is a cellular mechanism and
nothing more, developed during a single human life in
company with all other organs from a one-celled start-
ing-point — the human egg.

The method by which mental evolution has been
accomphshed is likewise demonstrable, because the
factors are identical with those which bring about
specific transformation in physical respects. This is to

232 DOCTRINE OF EVOLUTION

be expected, for the contention that the structures and
the functions of the several organs constituting any
system are inseparable has never been gainsaid.

Mental variatian is real. It needs no scientist to tell
us that human beings differ in intellectual qualifications
and attainments, and that no two people are exactly
similar even though they may be brothers or sisters.
The struggle for existence or competition on the basis
of mental abiUty is equally real, and every day we see
the prize awarded to the more fit, while those who lose
are crowded ever closer to the wall. As in all other
fields of endeavor, the goal of success can be attained
only by adaptation, which involves an adjustment to
all of the conditions of existence — to social and ethical
as well as to the more expressly material biological
circumstances.

Heredity of mental qualities has also been demon-
strated notably by Galton, Pearson, Woods, and Thorn-
dike, who have also shown that the strength of inheri-
tance in the case of mental traits is approximately the
( same as for physical characteristics like stature and eye-
j color. Just as a worker-bee inherits a specific form
of nervous system which cooperates with the other
equally determined organic systems, wherefore the
animal is forced to perform 'instinctively" its pecuUar
sp^ciahzed tasks, so the mental capacity of a human
being is largely determined by congenital factors.
Upon these primarily depends his success or failure.
It is quite true that environment has a high degree of
influence, so great indeed that some speak of a ''social
heredity" ; they mean by this phrase that the mental
equipment of an individual is determined by the

MENTAL EVOLUTION OF MAN 233

things he finds about him, or learns from others with-
out having to invent or originate them himself. Thus
a Zulu boy acquires the habits of a warrior and a
huntsman when he grows up in his native village,
although he would undoubtedly develop quite different
aptitudes if he should be taken as an infant to a city
of white men. Nevertheless his mental machinery it-
self would be no less surely determined by heredity,
even though the things with which it dealt would be
provided by an alien environment.

Our present knowledge of the nature and history of
human mentality enables us to learn many lessons that
have a direct practical value, although it is impossible
under the present limitations to give them the full
discussion they deserve. Starting from the dictum
\that physical inheritance provides the mechanism of
intellect, education and training of any kind prove to
be effective as agents for developing hereditary quali-
ties or for suppressing undesirable tendencies. Just as J
wind-strewn grains of wheat may fall upon rock and
stony soil and loam, to grow well or poorly or not at
all according to their environmental situations, so chil-
dren with similar intellectual possibilities would have
their growth fostered or hampered or prevented by
the educational systems to which they were subjected.
But the common-sense of science demonstrates that
the mental qualities themselves could not be altered in
nature by the circumstances controlling their develop-
ment any more than the hereditary capability of the
wheat grains to produce wheat would be altered by
the character of the ground upon which they fell.
Education and training thus find their sphere of use-

234 DOCTRINE OF EVOLUTION

fulness is developing what it is worth while to bring
out, and inhibiting the growth of what is harmful.
That heredity in mental as well as in physical aspects
provides the varying materials with which education
must deal is a fundamental biological fact which is too
often disregarded. It would be as futile for an in-
structor to attempt the task of forcing the children in
a single schoolroom into the same mental mold, as it
would be for a gymnasium master to expect that by a
similar course of exercise he could make all of his stu-
dents conform to the same identical stature, the same
shape of the skull, or the same color of the eye and hair.

Before leaving the subject of mental evolution we
must return to the conception of inseparable mind and
matter with which the present discussion began. The
whole problem of human mental evolution is solved
when we accept the conclusion that the nervous mech-
anism and the total series of its functional operations
have evolved together in the production of the human
brain and human faculty. The case regarding the
physical organs rests solidly on the basis of the evidences
outlined in a previous chapter; the special examina-
tion of purely mental phenomena has likewise been
made in the foregoing sections. Just here we must
pause to give further attention to the invariable rela-
tion between the human mind and the human brain.

The personality of human consciousness consists of
the current of thoughts and feelings flowing continu-
ously as one of them rises for a time to dominance only
to fade when it leads to and is replaced by another

MENTAL EVOLUTION OF MAN 235

dominant element of thought. This current is affected
by the messages brought to the brain by nerves from
the outer parts of the body where He the eye and ear
and other sense-organs. In hke manner the various
non-nervous parts of the body exert their influences
upon consciousness, but the affective processes, as they
are called, are not as well understood as the impressions
passed inwards by the sense-organs along their nervous
roadways to the central organ, the brain. But the
brain is the place where the thinking individual re-
sides ; and this is one of the most important teachings
of psychology, for not only does it help us to under-
stand the evidence that human faculty has evolved,
but it also inevitably brings us to consider certain vital
questions of metaphysics, such as the immortality of
the thinking individual after the material person with
its brain ceases to exist. However, the latter question
is something which does not concern us here; now it
is most important to realize how completely mind is
connected with the brain. — '

Many of the facts demonstrating this connection are
matters of common knowledge. In deep and dream-
less sleep the essential tissues of the brain are inactive,
and in correspondence with the cessation of material
events the thinking individual actually ceases to exist
for a time. Any one who has ever fainted is subse-
quently aware of the break in the current of human
consciousness when the blood does not fully supply the
brain and this organ ceases to function properly; a
severe blow upon the head likewise interrupts the
normal physical processes, and at the same time the
mind is correspondingly affected. Again, a progressive

236 DOCTRINE OF EVOLUTION

alteration of the brain as the result of diseased growth
causes the mind to grow dim and incapable. Some-
times infants are born which are so deficient mentally
as to be idiots, and an examination of the brain in such
a case reveals certain correlated defects in physical
organization. These and similar facts form the basis
for the dictum that the development and evolution of
the brain mean the growth and evolution of human
intellect.

The further question as to the nature of the connec-
tion is interesting, but it relates to matters of far less
consequence to the naturalist than the central fact of
the invariable relation which does exist. Throughout
the centuries many philosophers and naturalists of
numerous peoples have endeavored to explain the con-
nection in question in ways that have been largely
determined by the changing states of knowledge of
various periods, as well as by differences in individual
temperament. Three general conceptions have been
developed : first, that the material and mental phe-
nomena interact; second, that they are 'parallel; and
third, that they are one.

According to the first view, the individual thoughts
and feelings forming elements in the chain of consecu-
tive consciousness are affected by the events in the
material physiology of the brain as a physical structure ;
the latter in turn react upon the psychical or mental
elements. Thus there would be two complete series
of phenomena, which are interdependent and inter-
acting at all times, although each would be in itself a
complete chain of elements.

The second interpretation is that the two series of

MENTAL EVOLUTION OF MAN 237

events — namely, the physical processes of the brain
and the elements of consciousness — are completely
independent but entirely parallel. As one writer has
put the case, it is as though we had two clocks whose
machinery worked at the same rate and whose relation-
ships were such that ^^one clock would give the proper
number of strokes when the hands of the other pointed
to the hour." But in my opinion this attempted ex-
planation of the relation of mind to matter evades the
whole question, as it does not account for the depend-
ence of the former upon the latter, but merely assumes
the existence of a more ultimate and unknown group
of causes for a parallelism in the rates of operation of
two series of things regarded as disconnected.

The third conception recommends itself to many on
account of its greater simplicity. Formulated as the
doctrine of monisni, it states that the mind and its
materiallDasis are merely different aspects of one and
the same thing, and that there is only one series of
connected elements which are known to us directly as
the current of our thoughts and indirectly as the phys-
iological processes going on mainly in the cerebrum.
Thus mind is purely subjective, the brain is only me-
diately objective. It is because the mental and the
material are so intimately related that the monist
believes them to be connected as are the lungs and
respiration, the hand and grasping, or the eye and the
reception of visual impressions from without.

But whichever one of these explanations we choose
to adopt as our own, the basic fact of primary im-
portance is that there is an invariable dependence of
human thought upon a brain comprising a highly de-

238 DOCTRINE OF EVOLUTION

veloped cerebrum, whatever may be the ultimate nature
of the way mental processes are determined by physi-
cal processes, or vice versa. This fact stands unques-
tioned and unassailable ; human faculty and the brain
cannot be considered apart, even if they may not
actually be different aspects of the same basic " mind- _l
stuff," as Clifford calls the ultimate dual thing. ^

Like all of the other organs of lesser importance
belonging to the nervous system, the brain is a com-
plex of tissues which in the last analysis are groups of
cell-bodies with their fibrous prolongations. When these
cellular elements are in operation, mental processes
go on ; the. unit of the mental process therefore is the^
functioning of a brain-cell. But we know that the
substance of a brain-cell is the wonderful physical basis
of life called protoplasm, that demanded our attention
at the outset. The chemicals that go to make up
protoplasm are everywhere carbon, hydrogen, oxygen,
and other substances that are exactly the same out-
side the body as inside. It is the combination of these
substances in a peculiar way which makes protoplasm,
and it is the combination of their individual properties
which in a real even though unknown manner gives
the powers to protoplasm, even to that of a living brain-
/ cell. Does science teach us, then, that the ultimate
elements of human faculty are carbon-ness and hydro-
gen-ness, and oxygen-ness, which in themselves are not
mind, but which when they are combined, and when
such chemical atoms exist in protoplasm, constitute
mental powers ? Plain common-sense answers in,Jbhe
affirmative. We need not, indeed, we must not, attrib-
ute mind as such to rock salt or to the water of a

MENTAL EVOLUTION OF MAN 239

stream, but we do know that salts and water and other
dead substances may enter into the composition of the
material brain which is the physical basis of mind. i

In my opinion the individual argument renders the \
monistic conception of mind and matter unassailable.
The food that we may eat and the water we may drink
are dead, and as such they display absolutely no evi-
dence of nervous or mental processes. When they
enter our bodies, they with other foods replenish the
various tissues, and among these the parts of the brain.
In a material sense they become actual living proto-
plasm, replacing the worn-out substances destroyed
during our previous thinking ; and their properties are
combined to make brain and thought, to play for a
time their part in life, and to pass back into the world
of dead, unthinking things. Every one of us knows
that hunger reduces our ability to think clearly and
fully, and every one knows also that mental vigor is
renewed when fresh supplies of nourishment reach the
brain. What can be the source of mentality, if it is
not" something brought in from the outer world along
with the chemical substances which taken singly are
devoid of mind? Scientific monism frankly replies
that it is unable to find another origin.

We are thus brought to recognize, not only the
continuity taught by organic evolution, but also the
uniformity of the materials constituting the entire
sensible world, inasmuch as the ultimate unit of all
nervous phenomena is the reflex act of a protoplasmic
mass, which itself is a synthesis of properties inhering
in the chemical elements making up living matter.
Among inorganic things the mind-stuff units are com-

/

240 DOCTRINE OF EVOLUTION

bined in relatively simple ways, and the '' stuff '^ does
not give any outward evidences of ^^mind" as such.
Living things are almost infinitely complex as regards
their chemical organization, and even in the very lowest
of them we can discern a cell-reflex element which,
combined with others like it, forms the unit of the
compounds we call instinct, intelligence, and reason.
Hence through an analysis of mental evolution we are
enabled to form the larger conception of a continuous
universe whose ultimate elements are the same every-
where.

VII

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS

We now reach a critical juncture in our study of the
foundations of evolutionary doctrine, for we must pass
at this point to an inquiry into the nature and origin
of human social relations. In undertaking this task
we may seem to leave the field which is properly that of
organic evolution, and many perhaps will be unwilling
to view such aspects of human life as materials for purely
biological analysis, arrangement, and explanation. But
even before the reasons for doing so may be made
apparent, every one must admit that the subject of
mental evolution, which comprises so large a bulk of
details expressly social in their character and value,
virtually compels us to scrutinize the history of the
economic and other interrelationships maintained by
the human constituents of civilized, barbarous, and
savage communities. Language has been treated as an
individual mental product, and so have the arts of life
and of pleasure ; but all of these things find their great-
est utility in their social usage, — in their value as bonds
which hold together the few or many human beings
composing groups of lower or higher grade. Without
discovering any other reasons we would be impelled to
take up social evolution, for this process is inextricably
bound up with the origin and development of all de-
partments of human thought and action.

R 241

242 DOCTRINE OF EVOLUTION

If now this new field is actually to be included within
the scope of the laws controlling the rest of nature's
evolution, two general conclusions must be established.
Although no formal order need be followed, it must at
some time be shown that human social relations are
biological relations, to be best explained only through
their comparison with the far simpler modes of asso-
ciation found by the biologist among lower orders of
beings ; and in the second place it must be demon-
strated that identical biological laws, uniform in their
operation everywhere in the organic world, have con-
trolled the origin and establishment of even the most
complex societies of men. So far no reason has been
discovered by science for believing that evolution has
been discontinuous, holding true only for the merely
physical characteristics of humanity as a whole; and
furthermore, the impersonal student of nature finds
ample positive evidences showing that the basic laws of
associations of whatever grade are exactly the same.
For these laws we are to seek.

' Heretofore the doctrine of organic evolution has
been discussed with reference to the single individual
organism viewed as a natural object whose history
and vital relations require elucidation. Both in the
general arguments of the first few chapters and in the
fifth and sixth chapters dealing with the single case of
the human species, the proof has been given that all of
the structural and physiological characters of any and
every organic type fall within the scope of the prin-
ciples of evolution, by which alone they can be reason-
ably interpreted. It has been unjust in a sense to
ignore completely the importance of the organic rela-

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 243

tions of a social nature to which we are now to turn,
because no individual can exist without having its life
directly influenced, not only by other kinds of organisms,
but even more intimately by other members of its own
species. In a single day's activity we who are citizens
of a great metropolis are forced into contact with almost
countless other lives, glancing off from one and another
after influencing them to some degree, and gaining our-
selves some impetus and stimulus from our longer or
shorter intercourse with each of them. Our varied
social relations are so many and obvious that it is quite
superfluous to specify them as essential things in human
life. For the very reason that they are so obvious and
constitute so large a part of our daily life, we are in
danger of conceiving them to be exclusively human ; we
unconsciously regard them as different from anything
to be found elsewhere and quite independent of the
biological laws controlling the human unit.

On the contrary, as we trace the development of
social organization from its earliest rudiments it be-
comes ever clearer that evolution has been continuous, \
and that during later ages there has been no suspension
of the natural laws which earlier produced the human
type of organism. The lessons we have learned are by
no means to be ignored from this point forward ; all of
our conceptions of human biological history must be
kept in mind, for anything new that we may learn is
superadded to the rest, — it cannot disturb or alter
the foundations already laid. It is even more important
to realize that the same scientific method is to be em-
ployed which has been so fruitful heretofore. It has
given us interesting facts; it has indicated the most

I

244 DOCTRINE OF EVOLUTION

profitable lines of attack upon one and another scien-
tific problem; and it has demonstrated the practical
value of accurate knowledge, even of information about
the evolutionary process. As familiarity with the laws
of human physiology enables one to lead a more hygienic
and efficient fife, and as the results of analyzing the
evolution of mentahty make it possible to advance
intellectually with greater sureness, conserving our men-
tal energies for effort along lines estabhshed by heredi-
tary endowment, so now we are justified in expecting
that a clear insight into the origin of our social situation
and social obligations will have a higher usefulness
beyond the value of the mere interest inhering in our
new knowledge. Every one is necessarily concerned
with social questions; never before has there been so
much world-wide discussion of topics in this field. And
while it is true that much good may be accomplished
in utter ignorance of the past history of human insti-
tutions and of the underlying principles which control
the varied types of organic associations, surely enlight-
ened efforts will be more effective for good. Therefore
every member of a community who is capable of think-
ing straight rests under an obligation imposed by nature
to learn how he is related to his fellow-men ; he must act
in concert with them or else he forfeits his rights as a
social unit. And it is his clear duty to search among
the results of science for aid in ascertaining what he
ought to do, and what reasons are given by evolution
for the nature of his vital duties.

Despite the growing appreciation of the fundamental
relation between biology and sociology, it is still far
from universal. That the latter science is in a sense a

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 245

division of the former is more often recognized by the
biologist than by the average well-informed student of
human social phenomena. The layman in sociology too
often concerns himself solely with the complexities of
the human problems, and he remains unaware of the
manifold products in the way of communal organisms
far lower in the scale of life firmly established as primi-
tive biological associations ages before the first human
beings so advanced in mental stature that tribal unions
were found good. Among insects especially the biolo-
gist finds many types of organized living things, rang-
f ing widely from the solitary individual — a counterpart
of something even more primitive than the most unsocial
savage now existing — up to communities that rival
! human civilization, as regards the concerted effect of
i the diversified lives of the component units. The stu-
dent of the whole of living nature is favored still more
in that he learns how the make-up of such a simple
organism as a jellyfish displays principles underlying
the structure of the whole and the interplay of the parts
that are identical with principles of organization every-
where else. And all of these things can be dealt with
in a purely impersonal way which is impossible when
attention is restricted to the human case alone. Thus it
becomes the biologist's privilege and his duty as well to
place his findings before those who wish to understand
the constitution of human society in order that evils may
be lessened and benefits may be extended. He does this so
far as he may be able in full confidence that the elements
and basic principles are discoverable in lower nature,
just as they are in the case of the material make-up
and mental constitution of the single human individual.

246 DOCTRINE OF EVOLUTION

A more explicit preliminary statement must now be
given of the grounds for the behef that social evolution
is but a part of organic evolution in general. Some of
these reasons are not far to seek, but their cogency can
scarcely be appreciated until we have examined the
concrete facts of the whole biological series. Any
human society selected for examination — be it a
tribe, a village community, or a nation — is in last analy-
sis an aggregate of human units and nothing besides.
Its life consists of the combined activities of such com-
ponents — and nothing else. Could we subtract the
members one by one, there would be no intangible
residuum after all the people and their lives had been
taken away. When these simple facts are recognized,
it is clear at once that the concerted activities performed
by biological units cannot be anything but organic
in their ultimate basis and nature ; the evolution of
such activities thus takes its place as a part of organic
evolution.

The task of tracing out the history of social organi-
zations of whatever grade can now be defined in precise
terms : in simple words, it is to learn how the activities
of the component biological units making up any asso-
ciation really differ from the vital performances of
biological units existing by themselves. What is it
that distinguishes a savage of antiquity from an Ameri-
can of to-day? The modern example is just as much
an animal as the earlier type, and his physiology is
essentially the same. It is something added to the
common biological qualities of all men, some relation
which does not appear as such in the life of rude tribes,
that makes the distinction. And it is just this super-

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 247

added relation that requires explanation, as regards its
exact biological value and its historic development as well.
In undertaking this difficult task, it seems best to
begin with the very simplest organisms that biology
knows, working upwards through the scale to man. By
this course the most basic elements ol organization
can be discovered without having to look for them
among the intricate details of our own vital situation,
where secondary and adventitious elements stand out
in undue prominence, and where the impersonal view
is well-nigh impossible. Step by step we will then work
up the scale of social morphology, approaching in the
natural evolutionary order that part of the subject
which interests us most deeply.

Just as the construction of an edifice must begin with
the fashioning of the individual brick and bolt and girder,
so the evolution of a biological association begins with
the unitary organisms consisting of Single cells, like
Amoeba. We have had occasion to discuss this animal
many times in our previous studies of one or another
aspect of evolution, and once again we must return to
it in order to reestablish certain points that are of
fundamental importance for our present purposes.
Within the limits of its simple body. Amoeba performs
the several tasks which nature demands a living thing
shall do ; it feeds and respires and moves, continually
utilizing matter and energy obtained from the environ-
ment for the reconstruction of its substance and replen-
ishment of its vital powers ; it coordinates the activities
of its simple body, and by its reflex responses to en-

248 DOCTRINE OF EVOLUTION

vironmental influences it maintains its adjustment to
the external conditions of life. The animal does all of
these things with a purely individual benefit, namely,
the prolongation of its own life. While it is performing
these individual tasks, it does not concern itself with
anything else but its own welfare ; the interests of other
living things are not involved in any way, excepting in
the case of other organisms that may serve the animal as
food. Amoeba, like every other living thing, if it is to
exist, must unconsciously obey the first great command-
ment of nature, — '^Preserve thyself J ^

But its life is incomplete if it stops with the further-
ance of aims that we may call purely selfish. Nature
also demands that an Amoeba, again like every other
living thing, shall perpetuate its kind. The mode by
which it reproduces is ordinarily quite simple; the
animal grows to a certain bulk and then it divides into
two masses of protoplasm, each of which receives a
portion of the mother nucleus. Sometimes by a peculiar
process it breaks up into numerous small fragments
called spores, which also receive portions of the parent
nucleus. The most striking feature in both kinds of
reproduction in Amoeba is the complete destruction of
the individual parent that exists before the act and does
not afterwards. It is quite true that every part of
the mother animal passes over into one or another of its
products, but it is equally true that no one of these
products is by itself the original individual. So even
the simplest animal we know performs a task that is not
only useless to itself, but is completely destructive
of itself, for nature's greater purpose of preserving
the race. We can readily see why this must be so;

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 249

there is no place in the world for a species whose members
put individual well-being above the welfare of the race,
for which the production of new generations is essential,
even though the satisfaction of this demand should
necessitate the sacrifice of the parent organism. We
might hesitate to use the word ''altruistic" in describ-
ing the self-destructive reproductive act of an Amoeha,
because this word connotes some degree of conscious-
ness of the existence of other than personal interests,
and of the welfare of different individuals. There is
no reason to believe that such conscious recognition of
any natural duties is possible in the case of so low an
organism. But the fact remains that the result worked
out by nature is the same as though there were a definite
understanding of real duties. Even this unitary or-
ganism, then, acts mechanically so as to fulfil two primal
obligations, first to itself, through activities with indi-
vidual benefit as the result, and to the race by the act of
reproduction which closes its individual existence and
inaugurates a new generation.

The life of this example, representing the whole series
of one-celled organisms, is almost infinitely simpler
than that of a member of a human community, yet it
reveals the beginnings of certain characteristics of the
latter. Here, it is true, the natural obhgations in ques-
tion are not like those which are ordinarily denoted
social, but it is equally true that even in this most
elementary instance a living thing does not live unto
itself alone. It is easy to see the value to the species as
a whole of obedience to the second great law — "Pre-
serve thy kind.^^ But a little further thought makes it
plain that even the performance of acts in compliance

250 DOCTRINE OF EVOLUTION

with the first mandate — ^^ preserve thy self ^^ — are not
purely selfish, although their immediate value is realized
as individual benefit. Surely an organism that failed
to live an efficient individual life would be ineffective
in reproduction, so that from one point of view every-
thing an animal does is tributary to the culminating
act performed for the larger good of the life of the whole
species. It is a nice balance that nature has worked
out in Amoeba, as well as in all other cases, between the
personal life of the individual, complete only when the
final process of multiplication supervenes, and this
process itself, which demands an efficient performance,
even though this is destructive of the performer.

Before passing to the next members of the series, which
reveal additional principles more truly social in the
human sense, let us pause to note that already we have
found certain natural criteria that belong in the depart-
ment of ethics. Even in the case of the biological unit
like Amoeba, which is entirely solitary and unrelated to
other individuals of its kind excepting in so far as it is
a link in the chain of successive generations, any vital
activity can be called good or bad, right or wrong.
Nature judges an act good and right if it tends to pre-
serve the animal and the species ; an act is wrong and
evil if it is biologically destructive of the animal or if it
interferes with the perpetuation of its kind. Again
it must be pointed out that these terms are human words,
employed for the complex conceptions that belong alone
to retrospective and contemplative human conscious-
ness; to most of us they seem to imply the existence
of some absolute standard or ideal by which a given
act may be tested to see if it is right or the opposite.

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 251

If human ethics is truly unrelated to beginnings found in
lower nature, something that has arisen by itself from
supernature, then we must not use the terms in ques-
tion except by way of analogy. If, however, nature has
been continuous in the working out of every department
of human life and human thought through evolution,
then the criteria of the righteousness of the acts per-
formed even by an Amoeba may be found to be basic
and fundamental for ethical systems of whatever human
race or time. This subject remains to be discussed in
the final chapter, but it must be clear that we cannot
survey the evolutionary process by which social sys-
tems have come into being without deahng at the same
time with the origin and growth of ethical conduct as such.

Without leaving the group of one-celled animals
typified by Amoeba, we find colonies of the most ele-
mentary biological nature, where other natural obliga-
tions are added to the two of greatest importance.
Some species of the bell-animalcule, Vorticella, provide
characteristic examples of these primitive compound
protozoa. Here the assemblage is made up of one-
celled individuals essentially similar to one another in
structure and in physiological activities; in the latter
respect each one of them is like Amoeba as well. They
may remain together for a longer or shorter period, or
during their whole existence until the time of repro-
duction. Like the solitary protozoon, each member
leads a complete life in and by itself, equivalent to that
of every biological unit. It obeys the two great laws
already laid down, but in addition it seems to be required

252 DOCTRINE OF EVOLUTION

to remain with the others for some mutual good. The
biological value of the association which imposes this
additional obligation may be found perhaps in the fact
that a large group is not so readily eaten by an enemy
as an individual cell ; but it is clearer that the process
of reproduction, which consists of the fusion of small
^^ gametes," or nucleated fragments produced by diverse
or similar parents, must be greatly facihtated by the
occurrence of gamete-forming individuals in one and
the same colony. ^^To remain together ^^ is the new
duty imposed by nature for the good of all and for the
welfare of each member of the group. Some biological
advantage accrues to the several components, just as
the banding of wolves enables the pack to accomplish
something which the single wolf is unable to do, al-
though in the latter case it is not so much a reproductive
alliance that is formed as an offensive and defensive
union.

One step higher in the scale stands the plant-form
called Volvox, near the border-line between the one-
celled and the many-celled organisms. This aquatic
type, about the size of the head of an ordinary pin, is a
hollow spherical colony, with a wall composed of closely
set cellular components. These elements are not all
alike, as in the case of colonial protozoa like Vorticella,
for they fall into two classes which are distinguished
by certain structural and functional characteristics.
Most of them are simple feeding individuals which
absorb nourishment for themselves primarily, but they
pass on their surplus supplies to less favored neighbors
if occasion demands. The other members begin life
like the first-named, but later they become specialized

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 253 i

'i

■1

to serve as reproductive individuals solely. Every \
member of the colony must obey the first precept of \
nature, otherwise it would be unable to play its part in i
the life of the whole community. But the discharge of ! i
the second natural obligation, namely to preserve the ; |
race, is here assigned to some, and to some only, of the | V
whole group of cell individuals. It follows therefore i !
that the division of the tasks necessary for the mainte- ' ^
nance of a complete biological individual, and the differ-
entiation of the members of the group into two kinds,
leads to the establishment of an individuality of a
higher order than the cell. Neither the purely nutritive
nor the reproducing member is complete in itself;
the two kinds must be combined to make a perfect
organism. The life of any member can be selfish no
longer, for if it is to exist itself, it must help others for
the mutual advantage of all. A clear social relation is
thus established ; and the reflex conduct of the units
of a Volvox colony can be justly denofeH ^altruistic,
eT^""tliough in this case, as before, there can be no con-
scious recognition of the reasons why mutual interests
are best served by what is actually done.

One of the most interesting and significant aspects
of the life-history of Volvox is the appearance for the
first time of biological death. More elementary or-
ganisms are immortal potentially even if not actually,
for every portion of the body is capable of passing over
into an animal of a succeeding generation. But in
Volvox a division of labor has been effected of such a
nature that most of the components discharge the tasks
of individual value, and with the performance of these
they die. Only the reproductive members are immortal

254 DOCTRINE OF EVOLUTION

in the sense that Amoeba is, for they only have a place V
in the chain of consecutive generations of Volvox j
colonies. From the standpoint of the nutritive indi- '
vidual it is better to be relieved of the reproductive task
in order that there may be no interruption of its special-
ized activities for the good of all, but the entailed mor-
tality is certainly disadvantageous to it. It is the higher
interest of the colony as a whole that supersedes the
welfare of the parts taken singly, and this larger welfare
is safeguarded by a differentiation worked out by natu-
ral evolution which results in the assignment of personal
and racial duties to different individuals, at the cost
ultimately of the lives of the former.

We now reach the realm of the true many-celled
animals, or Metazoa, where the biological units are
combined to form an organic association displaying many
more resemblances to a human society. The fresh-
water polyp Hydra, like the foregoing illustrations, is
one whose structure has already been discussed in the
earlier chapters, but now we may use it for an analysis
of another series of biological phenomena. Its sac-like
body consists of two cell-layers ; the outer one is con-
cerned primarily with offense and defense, while the
inner layer is made up of digesting or nutritive elements.
The essential cells concerned solely with reproduction
lie below the outer sheet. Comparing this animal with
an association like Volvox, we discover the same differ-
entiation into immortal germ-elements and mortal
cells, concerned respectively with the Hydra's racial
existence and with its individual life ; but far-reaching

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 255

changes have come about in the biological relationships
of the second class of cells. In describing the new phe-
nomena it is absolutely necessary to employ the terms
of human social organization, because the Hydra's
body is a true colony of diverse cells in exactly the same
sense that a nation is a body of human beings with more
or less dissimilar social functions.

To begin with the differentiation into ectoderm and
endoderm, the organism is comparable to a human com-
munity made up of military and agricultural classes.
The cells of the former group protect themselves and
the feeding elements also, while the units of the second
defenseless type devote themselves to the task of pro-
visioning the whole community, giving supplies of food
to the defenders in exchange for the protection they
afford; each kind needs the other, and each performs
some distinctive task for the other as well as for itself.
But the parallel thus drawn need not stop here. In the
case of the outer layer, the cells are mostly flat covering
elements that are the first to be torn off and injured
when the animal is attacked. Scattered about among
them are sense-cells standing like sentinels with deli-
cate upright processes which receive stimuli from with-
out ; the sense-cells transmit impulses to the network of
nerve-cells below, which is a counterpart of the signal
corps of an army, keeping all parts of the whole organi-
zation in communication with one another. Most
wonderful of all are the stinging-cells of the outer layer ;
these produce a flask-shaped, poisoned bomb which is
discharged by the convulsive contraction of the cell it-
self so as to stun and injure the enemy or prey. The
bomb-throwing cells die immediately after they have

256 DOCTRINE OF EVOLUTION

ejected their missiles; like soldiers participating in a
forlorn hope, they sacrifice their lives in one supreme
effort of service to the cell-community of which they
are members.

These and similar facts prove conclusively that
Hydra is a true community even in the human sense,
and that the laws of biological association are estab-
lished at a point far below the level of the insects. The
individuality of the unit is still maintained, and each
cell must guard its own interests to a certain degree,
but the original independence of the unit has become
so altered by differentiation and division of labor that a
close interdependent relation has come about. The
complete individual is now the whole aggregate; it is
the entire Hydra itself which must obey the primary
commands of nature to live efficiently and to perpetuate
its kind. True it is that the life of the higher individual
is the sum total of the activities performed by its con-
stituent cells, but no one of the varied specialized ele-
ments is biologically perfect by itself or equivalent to
the whole. And, as we have seen, the welfare of the
complete animal takes precedence over that of any one
of its parts, just as the existence of a nation may be
preserved only by the death of soldiers warring for its
honor and life.

If, now, we should pass on to the more complex or-
ganisms like worms and insects and vertebrates, and
should disregard the communal relations of some of
these animals, each individual proves to be like Hydra
as regards the principles underlying its make-up and
workings. A single bee, like a man, is a definitely con-
stituted aggregate of cells, differing as a whole from

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 257 ^

I

Hydra only in the degree of differentiation exhibited by

its constituent elements. Instead of a loose network j

of nerve-cells there is the far more complex nervous i

system whose evolution has been outlined in the sixth j

chapter. The blood-vascular and respiratory and ex- 1

cretory systems have become well organized, in response, i

so to speak, to the demands on the part of the nervous i

and alimentary organs that they may be relieved of the \

tasks of circulation and respiration and the discharge J

of ash-wastes. Therefore the cells which make up an i

insect and a man are more diverse, they have more ^

varied interrelationships, and they are far more inter- i

dependent then in the case of the components of Hydra. i

Yet all the many-celled organisms that we are so accus- \ a j

tomed to regard as individuals are really communities, : L* '

dejnan&trating the existence and partial antithesis of | / *^

the great laws of egoism and altruism, wliich are trace- f .

able even down to AmoBha 2iRd its like. / i

'J

So much has been made of the lower kinds of cell-
associations because the mind of the layman is uncon- j
sciously imbued with the idea that human society is a |
new thing, — an idea which we now see it is necessary ;
to discard at the outset. Indeed, the cell-association !
of the Hydra and insect type is a more compact and a j
more stable kind of community than any group of
human individuals worked out by nature toward the i
present end of the whole scheme of evolution. That j
is to say, the subordination of cell-interest to cell-group I
welfare, while it must not go so far as to render the unit -
incapable of doing its work, is_jufficiently advanced to ;
make uncontrolled individualism impossible. Let any I
class of Hydra^s cells, such as the nerve or muscle net-
s

258 DOCTRINE OF EVOLUTION

work, assume to exercise a selfish preeminence or to
conduct a ^'strike/' the other classes, like the feeding
cells, would not be properly served and they would be
unable in consequence to work efficiently for the strikers.
The immediate result would be suicidal, for the selfish
nerve-class would inevitably suffer through the downfall
of the whole social fabric. It is a nicely adjusted
equilibrium that is established, where the ^' equal
rights" of all the diverse cells consist in freedom to play
a special part in the life of the group, serving other
individuals in return for their service. The Golden
Rule is a natural law as old as nature ; for even in
Hydra! ^ life, unconscious discharge of duties to the race,
and hence to others, is obligatory. And all these low
types of organic associations evolved ages before the
rules of human social order were vaguely recognized
by the reflective self-consciousness of man, to be for-
mulated as the science of ethics.

The evolution of the wonderfully varied societies
found among insects begins with the solitary insect
itself, just as this, viewed as a cell-community, origi-
nates from one-celled beginnings like Amceha through
progressive evolution in time. The similarity between
social insects and human associations is clearer than
in the case of a comparison between an example from
either group and a cell-community, because the higher
forms lack the organic contact of the components which
is so prominent a feature in the lower instance. The
social bonds are looser and they allow a freer play of the
constituents ; but nevertheless the same lav/s that con-

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 259

trol the activities of the cells making up what we now
take as the individual element, command obedience
on the part of the interrelated members of an insect
community with equal strictness.

A butterfly or a moth is primarily egoistic and unso-
cial in the ordinary sense during its entire life-history,
until the final reproductive act which has a value to the
species. The caterpillar larva devotes all of its energies
to feeding and growing, unconcerned with the final
duties of the moth with which it is connected just as
the indifferent unit of a young Volvox colony is related
to a reproducing member of the full-grown organism.
Now and then, it is true, species like the so-called tent
caterpillar are met with where numerous larvae spin
silken communal nests to which they retire at night
and in which they remain to molt. The pupa, like
the larva, is individualistic and employs its time in
producing the final adult form. The mature individual,
however, is constructed almost solely for the greater
purpose of perpetuating the species. Indeed the larger
silkworm moths do not and cannot feed, and their
value is only that of a device for keeping the race estab-
lished. Adult may-flies live only a few minutes, just long
enough to provide for the fertilization and deposition of
the eggs, although to prepare for these acts the young
individuals must have toiled for months ; the preparatory
time may amount to many years in such a case as the
seventeen-year locust. But nature is satisfied, as long
as the organic mechanisms obey her double command-
ment, ^^Live and grow so as to multiply." Like an
Amoeba, the solitary insect must be egoistic at first, in
order to be altruistic in a racial sense in its last days.

260 DOCTRINE OF EVOLUTION

Wasps, bees, and ants provide many familiar examples
of colonial organizations that become all the more mar-
velous on closer acquaintance, on account of their
resemblances to human associations on the one hand,
and to cell-associations on the other. Their illustrative
beauty is enhanced by their wide variety, for they grade
from counterparts of highly civilized men down to a
savage among insects, such as the strictly solitary
digger-wasp, whose instincts served to exemplify the
insect type of '^mentality" in the discussions of the
preceding chapter.

The true communities founded by wasps and hornets
must be assigned to a low grade in the scale because they
originate during a single season and break up at its
end ; for this very reason the wasp community is in-
tensely interesting to the student of comparative social
evolution. In the spring a solitary female emerges
from the crevice where she has hibernated and resumes
active life ; she feeds for a time to renew her strength
and then she constructs a simple nest of mud or masti-
cated wood-pulp. In the first few cells of this nest she
deposits her eggs, and when they hatch she herself
provides the larvae with food, but still continues to
enlarge the house and to produce more eggs. Thus
during the first few weeks of the colony's existence this
single individual performs a variety of tasks of racial as
well as of purely egoistic value ; but as time goes on, a
profound change comes about in her activities and in
the life of the whole community. The members of the
first brood do not grow into counterparts of their mother ;
they are all sexless ''workers" who progressively reheve
their parent of the tasks of nest-building and foraging

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 261

and nursing, so that their mother becomes a ' ^ queen '^
who devotes her entire time to the special reproductive j
task which she only can perform. We may justly '
compare the queen to the reproductive organ of Hydra,
for the values to the life of the species are identical in
the two cases, while the various classes of workers are
counterparts of such units as the muscle and nerve and
nutritive components of the Hydra or any other cell-
community individual. Another resemblance between
the two is found in the death of all the sexless individuals
at the end of the season, when reproducing males and
females are finally formed, of whom the fertile queens
only survive in their winter hiding places ; and again
we can discover the cause for biological death in that
division of labor which calls upon certain members of
the whole community to perform tasks that have no
value when once provision has been made for perpetuat-
ing the species. Finally the mode by which the colony
grows and amplifies is in all respects like the embryonic
development of an egg into a Hydra, so that we may add
the phrase ^^gocial embryology " to our vocabulary. The
original female is an undifferentiated master of all
trades; the small tribe she first establishes is httle
better off than a horde of savages ; but during its sea-
sonal existence the community increases in numbers
and complexity until it advances well toward the civi-
lized condition, when each class performs its special
task for the good of all.

The bees take us higher in the scale, although many
solitary species occur, as well as social forms like the
bumblebees where colonies are formed in a single
season only to break up with the advent of cold weather.

262 DOCTRINE OF EVOLUTION

The honeybees, however, establish permanent com-
munities from which swarms may set out during the
warm months to become new colonies elsewhere. Many
hundreds of bees make up a hive, and they belong to
three classes or castes, which differ in structure and
social function. The queen is a fertile female, the
drones are males, and theVorkers are stunted and in-
fertile females which take no part in reproduction. In
this case the queen never discharges any menial duties,
for these are attended to by the workers ; she devotes
her entire time to laying eggs, which are cared for by
her subjects, who act as nurses and guards for the mon-
arch as well. The young workers serve at first as door-
keepers, and only later do they take the field in the
search for nectar and pollen, and work as house-build-
ers. Each individual performs its special task for its
own benefit and for the weal of all ; each possesses an
equal right to share in the prosperity of the whole com-
munity so long as it acts altruistically as well as egois-
tically. And just as the welfare of Hydra is superior to
that of any one of its constituent cells, so the well-being
of a hive of bees may be safeguarded only by the actual
sacrifice of some of its members. Should food supplies
be inadequate, the superfluous drones are stung to
death, — the victims of legalized murder. But more
marvelous still is the provision that is said to be made
by certain individuals for their own destruction should
this become desirable. As every one knows, a reigning
queen may leave the hive with many of her subjects and
''swarm'' in a new locahty. When she does this, dur-
ing the warm months, the workers of the original hive
feed some of the female larvae with richer food, and place

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 263

these potential queens or princesses in special roomy-
cells apart from the ordinary brood chambers ; one of
them soon emerges to become a new sovereign. Let us
note in passing how similar this is to the production of
new egg-cells in a Hydra, when the mature germs of an
earlier generation are prepared and discharged. When,
now, the colder weather sets in, and the possibility of
subsequent swarming is set aside, the reigning queen is
allowed by her attendant guards to visit the royal cells,
whose occupants she stings to death, thus destroy-
ing any possible claimant to her place. And when the i
royal princess constructs her part of the pupal case,
she leaves an aperture so that if and when it should j
become necessary for the queen to kill her, the sovereign
would not injure her sting and be unable to kill the other ,
individuals who might become aspirants for the throne
and so precipitate a civil war ! As in the case of the ^7
self-destructive act on the part of a stinging cell in
Hydra, altruistic subservience to the interests of the
colony can go no farther.

The ants form stable colonies of still higher grades,
where the workers are not all alike in general structure,
but become more rigidly specialized for the performance
of restricted tasks. As before, there is the fundamental
differentiation into the sexual '^queens" and males, and
the sterile workers concerned with the immediate
material life of the community. In some species the
workers serve as herdsmen, caring for the ant-cattle or
aphids, from which they receive minute drops of a
sweet juice for food. The aphids are tended on the
leaves of various plants during the summer, and are
carefully reared and stabled and fed below ground during

264 DOCTRINE OF EVOLUTION

the winter months. In other species seeds are procured
and stored in underground granaries. The leaf -cutters
are forms which grow food supphes of fungi in sub-
terranean mushroom gardens; the compost consists of
cuttings brought from the leaves of bushes by myriads
of workers, whose processions are guarded by larger-
headed soldiers of several ranks. In the honey-ants of
Colorado and tropical America certain individuals pass
their time suspended from the roof of a large nest-
chamber, where they receive the sweet juice brought
in by the workers. They serve as animated preserve
jars, distended some times- to the size of a grape with the
communal stores of food, which they return to the
workers when external sources of food may fail. Finally
there are the slaveholding species which conduct
forays upon the nests of other forms, to procure the
young of the latter, which grow up in their captors'
nests and serve them as nurses and masons and foragers.
So long has this custom been established that some
slaveholders are entirely unable to feed themselves,
and would die out if their slaves failed to support them.

Let us pause at this point to summarize the results of
the foregoing analysis, in order that we may approach
the biological study of human associations with definite
and clear conceptions of the fundamental laws control-
ling living communities of all grades.

We have dealt mainly with Amoeba, Hydra, and the
ant-community which exemplify three somewhat dis-
tinct types of organic individuality. Some of the
transitional forms have been specified to show how the

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 265

second kind originates from the first, and how in its turn
this grows in time into the third and most complex
association ; thus Vorticella and Volvox connect Amceba
with the cell-community individual Hke Hydra and a
sohtary wasp, while the annually established colonies
of social wasps and of bumblebees lead to the permanent
colony-individual. Restricting attention to the three
primary examples, ,and remembering tliat the criterion
of completeness is the ability to discharge satisfactorily
all of the eight biological tasks, it is clear that the entire
Hydra and the whole ant-cornmunity correspond physio-
logically with Amoeba, although the first-named is
structurally a cell-community equivalent to many pro-
tozoa, and the insect colony is composed of many such
cell-communities as elements. In the third type,
neither a single queen nor a single worker is able to
carry on all of the biological tasks any more than a
muscle-cell or an unformed egg of Hydra can maintain
itself capably in isolation. Therefore the ant-society
as a whole and the Hydra in its entirety are organic
individuals on the same physiological plane with
Amoeba, and they are equally subject to the same great
laws of nature demanding selfish maintenance and ra-
cial perpetuation.

But we must not lose sight of the fundamental value
of the unit during the evolution of a higher from a lower
type. The tissue-cell of Hydra must still obey the
mandate to live an efficient personal life, because this
is necessary for the welfare of other cells and of the
whole complex. The original egoistic tasks are not
abolished, but new duties are added to them in ways
we have learned to distinguish. In Vorticella the

/

266 DOCTRINE OF EVOLUTION

products of fission do not separate, and certain advan-
tages accrue from the organic continuity thus main-
tained. The success of Hydra in its ceaseless struggle
to live depends wholly upon the cooperation of its
differentiated cell-units, now no longer equivalent in
function to the all-powerful Amoeba, although each one
must be kept alive until its task is done, or the whole
association would have no place in nature. Similarly
in the higher insect community, the superadded duties
to fellow-components are even clearer, for in the compe-
tition of colony with colony, involving terrific battles
whose casualties may be numbered by thousands, the
stronger wins; and strength depends upon the con-
certed efforts of all the members of the kingdom, that
only collectively constitute a complete biological whole.
Mere self-protection demands altruistic conduct : if
the worker ceased to bring in food when its own hunger
was satisfied, there would be no tribal stores for the
stay-at-home queens and nurses; and if the soldier
fled from the field of battle to save its own life, its act
would be suicidal ultimately, for to the degree of one
unit the defense of its non-military supporters would be
weakened and they would be so much the less unpro-
tected during their service for the soldiers and all others.
Furthermore, we must admit the reality of natural
criteria of ethical values, established far below mankind
in the scale of life. In an ant-republic, laws are in-
stinctively obeyed quite as implicitly as though they
were intelligibly proclaimed to all of the emmet citi-
zens. Right is might when community battles with
community, for right is that which is biologically favor-
able. And what may be correct conduct on the part

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 267

of the members of one species may be naturally wrong
and evil in another case. To kill the princesses in order
to obviate the possibility of civil war seems advanta-
geous and therefore right when the queen remains in
the persistent colony of honeybees, ready to do her part
the following spring ; but it might result in disaster and
evil in the case of the social wasps, where the community
dies as such in the fall, and the continuity of the species
from one year to another requires the production of
many queens lest the severe conditions of the- winter's
hibernation should kill all fertile females if only one or
two were available. The standards of conduct are
simple indeed; and whether or not it may seem best
to separate the processes of social and ethical evolution
culminating in human phenomena, the fact remains
that these processes begin with elements discovered by
the biologist among organisms of the lower levels in the
scale. ^

We come at length to the biological interpretation of
human social evolution, in so far as this may be ex-
pounded in a simple and concise form. The compara-
tive method must be employed in order to discover the
fundamental attributes of savage, barbarous, and civilized
communities which seem to differ so considerably in
their complexity of social structure, and in order also
to show that such basic elements are like those of com-
munities formed by lower animals, and are equally the
products of natural evolution. This whole subject
seems to be exceedingly complex, because in our daily
contact with others of our kind and in our occasional

268 DOCTRINE OF EVOLUTION

views of foreign races like our own^ the smaller details
occupy our attention, diverting it from the great basic
principles according to which every society is organized
and operates. But when once the major elements have
been discovered in civilized and more primitive nations,
the secondary and less essential phenomena fall into
their proper relations, and a statement of the whole
process of development becomes relatively simple.
So much space has been devoted to lower types of
communal organisms in order to learn what the funda-
mentals are, and not merely to provide analogies that
may be useful hereafter. It now remains to arrange
the evidences of social progress during the history of
mankind itself, and to bring such human facts into
relation wdth what has been discovered in lower nature.
It is helpful to begin this part of the subject by asking
ourselves what is already part of common knowledge
about human history. Do we know of any civilized
nation that is absolutely stable and unvarying in social
structure, or one that has remained unchanged through-
out historic time ? The answer must be negative, for
in no case does the past disclose an example of per-
manence in social or in any other respect ; monarchies
and republics are plastic like the human frame itself.
The American Commonwealth is a relatively young
social organism, and it is an easy task to trace its growth
from beginnings in the diffuse and uncorrelated colonies
of pre-Revolutionary years. Those colonies that were
formed by English settlers were transplanted out-
growths from a civilized social parent which in its turn
had clearly evolved from the state of King John's time
and the still cruder form it had under King Alfred.

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 269

Should we follow back the recorded history of any
people now civilized, we would always find evidence of
ceaseless change ; and the writings of ancient historians
like Herodotus and Csesar and Tacitus give a great deal
of information about the barbarous conditions from
w^hich civilization evolved.

But much more is known that materially amplifies
the account of human progress based upon documents
alone. The student of existing human races early learns
that social structur£,is a very varied thing. The natives
of northern Africa now live in a semi-civilized state
which is very like that of medieval England. In
Siberia and the American Southwest are tribes that
correspond socially with the barbarians of Europe de-
scribed by Greek and Roman writers. The American
Indians discovered by the earliest colonists, the Poly-
nesians of a century ago, and the Fuegians of recent
decades provide counterparts of the ancient stone-
wielding people who were the savage ancestors of Euro-
pean barbarians. Hence the comparative study and
classification of modern races establishes a scale of
social grades which corresponds with the order of their
historic succession, just as in a larger way the complete
series of comparative anatomy from Amoeba to man
displays the order of evolution from unicellular be-
ginnings to the present culminating types. Savagery,
barbarism, and civilization are the three major terms
of this social scale, but by no means are they discon-
tinuous, for many intermediate forms of organization
occur which are transitional from one major type to a
higher one.

In human social evolution the starting point is not so

270 DOCTRINE OF EVOLUTION

simple as the solitary unit from which insect societies
evolved, — that is, an organism which lives alone and
is associated with another of its species only at the time
of mating. The lowest human beings now existing
have some form of family organization, traceable to
the more or less continuous unions formed among cer-
tain of the apes and even among many lower animals,
and not a characteristic that belongs to mankind alone.
The savage and his mate constitute the social unit out
of which all else is built up ; the man and the woman
must perform all of the vital tasks demanded by nature.
Fruits and vegetables must be secured from the wild
forest or by cultivation; the flesh of game animals
or of a human victim is no less essential for food. The
savage is his own weapon maker and warrior ; he him-
self builds the rude shelter for his family and fashions
the canoe if such is required. He is also his own judge,
recognizing no control save the dictates of his wishes
and needs, for he does not consciously realize that he
mtist obey the primal commands of nature to preserve
himself and his family so that the species shall persist.
In brief, the elementary family unit carries on all of
the individual biological tasks of foraging, fighting,
home-building, and the like, and it also discharges the
racial task of multiplying, quite as instinctively as it
provides for its own maintenance.

By the union of several families, a primitive associa-
tion arises, Hke that of the Veddahs in Ceylon. The
primal duties of each family are unchanged, and their
biological activities are identical, as in the protozoon
colony of Vorticella or in a pack of wolves ; but certain
new relations are established. A member of such an

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 271

inchoate tribe must not treat his confreres as he might
a man of another group ; robbery and murder within
the limits of the small association are detrimental to
communal interests, though they may remain unchecked
if the victims are strangers. Cooperation for mutual
offense and defense makes the group stronger than its
constituent family units taken singly, and every man
of such a tribe gains something by looking out for others
as well as for himself. By natural selection alone the
bonds of union would be strengthened in direct pro-
portion to the subordination of individual interest
to group welfare, and to the amount of altruistic
action that in a true sense grows out of purely selfish
conduct.

But when such a primitive biological association forms
and grows, an opportunity arises for increasing the
effectiveness of the whole group by differentiation.
Some of the men are stronger in battle and they soon
become the chief warriors ; others prove to be more
skilful in the hunt or in the construction of canoes and
weapons. Just as among the insects, the hunter seeks
food not only for himself but for the warriors, who in
their turn defend themselves, but do not cease fighting
when they have disposed of their own enemies if foes
of their comrades still survive. The barbarous state of
society thus arises, and the division of labor brought
about during its origin makes it possible and indeed
essential for many family units to remain together for
mutual good. The union is stable and efficient, how-
ever, only if the individual suppresses his own selfish
inclinations, suspending private quarrels when public
wars are toward, and acting at all times in concert with

272 DOCTRINE OF EVOLUTION

his fellows. Self-control increases necessarily, and
lines of conduct deemed right by a solitary savage
unit come more and more under the sway of social
inhibition, for although the primitive savages must
inhibit individualistic action to some degree, the bar-
barian must suppress much more of his purely personal
wishes for the purpose of social solidarity. Thus it
comes about that a barbarous community can number
thousands, while a tribe of savages with a higher degree
of individualism and less altruism cannot cohere if it
comprises more than hundreds or scores.
\ Civilization is a product of evolution by precisely the

I same natural mode of development, that is, through
/ further subordination of individual to communal inter-
! ests and through progressive dividing up of the tasks
I necessary for the life of the group. The final result
i is so obvious and familiar that we take it for granted,
accepting it as self-sufficient without realizing how it
has come about and how modern is the present state
of affairs. Let us compare the life of an Indian savage
living on Manhattan Island four centuries ago with that
of a New Yorker to-day, as regards so simple a matter
as the procuring of fish food. The Indian emerged from
his tepee, built by himself, and walking to the shore,
stepped into a canoe which also he had made with his
own hands. PaddHng to the fishing ground, he pa-
tiently cast his line until the desired fish were caught.,
Does any one of us do all of these things for himself?
We live in houses constructed for us by others who
devote their lives to building; we are very apt to go
about the city in conveyances that demand special
and peculiar skill for their invention, manufacture, and

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 273

operation. Arriving at a market-place, we obtain such
an article of food as a fish without having to go out upon
the water ourselves, for many other workers have built
vessels that we do not know how to make and may not
know how to handle, and hundreds of fishermen devote
their lives to their special task, not for themselves, but
for us and all others, such as the builder, the subway
operator, the boat maker, and the manufacturers who
supply their clothing and apparatus.

What has come about then is a higher degree of
specialization in the performance of the fundamental
biological tasks, resulting in the formation of coherent
and efficient groups comprising millions as compared
with the thousands of barbarism and the hundreds of
savagery. Just so the communities of insects with the
greatest degree of altruism and division of labor far
exceed in numbers the small colonies of the social wasps
with lower social differentiation.

But the great biological functions of an entire com-
plex civilized society remain the same as those of a
primitive savage family unit, of an insect community,
of Hydra, and of Amoeba. Let any nation fail to main-
tain itself in material individual respects, it must inevi-
tably die out ; in the islands of the South Seas many a
tragic death-struggle of a people can be witnessed. If
in the second place a nation should concern itself too
greatly with the material benefits of human life without
obeying the natural mandate to propagate itself, its
place in the scheme of things becomes insecure, as in
the case of the French Republic. Natural social laws
that go back to Amoeba must be observed, consciously
or unconsciously, or else even the civilized community

274 DOCTRINE OF EVOLUTION

must fall, like scores and hundreds of others that lie
along the road of historic progress — a road strewn with
the remains of the unfit thrown out by natural selection.

What now are the lessons of social evolution and what
guidance does science give for human endeavor? Al-
though it may seem that the biologist leaves his field
when he considers these questions, his duty would be
unfulfilled if he neglected an opportunity to give his
results their highest utility through their use for the
betterment of human life.

The first lesson is that the history of human social
organization is far from unique, and that it is identical
with the process by which insect communities and cell-
aggregates have evolved ; in a word, the laws of bio-
logical association are uniform throughout the entire
organic scale. In some respects evolution in mankind
has yet to equal the heights attained by some insects,
inasmuch as no human society has accomplished so rigid
a specialization of its members that a given individual
is foreordained by its inherited structure to be a par-
ticular kind of worker and nothing else. Furthermore,
evolution in human society is still far short of a state
where some and some only are reproductive members
of the group while the others are necessarily sterile;
social insects with stable colonies are so organized that
the queens and drones are solely reproductive while the
workers are destined to care for the material wants of
the colony. It is true that the birth-rate is by no means
the same in all classes of society, but the social and
other adventitious restrictions that bring this about are

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 275

not on the same plane with the hereditary determin-
ing factors which operate among insects. Therefore
the scale of human communities proves to be only
a part of the wider range of organic associations in
general — a part which can be definitely placed in such
a wider scheme and so become more intelligible in
itself.

In all departments of social evolution, progress is
made by the twofold process of combination and differ-
entiation. We have dealt with detailed instances, and
now it is profitable to treat the process in a larger way,
with a view toward the possibilities of the future.
The Thirteen Colonies, somewhat similar in their
earlier economic activities, united for mutual support
much as wolves combine to form a pack. Later, as
circumstances directed, they differentiated into farming
or manufacturing or commercial organs of the body
politic, each to some degree freeing itself of the functions
undertaken by others, and becoming thereby more
dependent than before upon those that specialized in
different ways. As in the history of the insects in a
growing wasp community and of savages evolving into
barbarians, the original condition of relative indepen-
dence passed into a state of interdependence and coop-
eration. In like manner, if nature remains the same, as
there is every reason to believe it will, nations now sepa-
rate will unite to make more complex combinations that
will be veritable empires of world-wide scope. Countries
on opposite sides of an ocean are now more closely con-
nected by lines of communication and means of travel
than were the Carolinas and New England a century
ago. Diplomatic activities give many signs of a grow-

{

276 DOCTRINE OF EVOLUTION

ing appreciation of the value of reciprocal agreements
for mutual advantage, and the Hague Conference is a
concrete manifestation of a continuing process of social
evolution that finds its beginnings and its interpretation
far below human history in lower organic nature.

But perhaps the most important result of this whole
discussion is the lesson of social service that it teaches.
We are members of a vast community whose complex
total life seems far removed from anything going on in
an ant-colony, and our daily tasks vary greatly in
specific character and degree when compared with those
of lower communal organisms. It seems scarcely cred-
ible that any principles of social relationship, however
general, can hold true for us and for them. But when the
rock-bottom foundations are reached, they are simple
and instructive indeed. Being here, we cannot escape
our personal obligations as living things or our equally
clear duties as members of our community. These
facts being as they are, what must we do? Self-
interest is rightly to be served, otherwise we would be
incapable of discharging our secondary tasks, namely,
those of service to others in ways that are determined
by hereditary endowment and conditional circumstances.
/ The difficulty is to find the right compromise between
the two sets of obligations ; but the right balance must
be found, or else the health of the community is im-
paired. Should any class demand more than its just
dues, others must suffer through the diversion of what
they require, and the well-being of the selfish class is
jeopardized to some degree, so closely interwoven are
the interests of all. Freedom of opportunity within
the limits of ability and efficiency is the right of every

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 277

one, but freedom of conduct must never result in tres-
pass upon the equal rights of others to make the most
of their abilities and opportunities.

To summarize, then, social evolution is a continuous
process accomplished through differentiation and divi-
sion of labor among the components of biological asso-
ciations. Although the total form remains the same
everywhere, progress has been made in content through
the further subordination of selfish to altruistic conduct ;
only by this means does an individual gain liberty to
pursue the social task for which he is best fitted by
nature.

VIII

EVOLUTION AND THE HIGHER HUMAN LIFE

We have now reached the last division of the large
subject that has occupied our thoughts for so long.
The present title has been chosen because the questions
now before us relate to the highest human ideas belong-
ing to the departments of ethics, rehgion, theology,
science, and philosophy. These matters may seem at
first sight to be far removed from the "territory of the nat-
uralist as such, and quite exempt from the control of laws
which determine the nature and history of the human
individual in physical, mental, and social respects.
Yet one reason alone would impel us onward : we can-
not close the present examination into the basic facts of
evolution and into the scope of the doctrine without ask-
ing to what extent a belief in its truth may affect our
earlier formed conceptions of nature and supernature.
Heretofore these possible effects upon what may be
dearly cherished intellectual possessions have received
no attention, so that we might learn how evolution
works in the lower fields of organic life in general and
human life in particular without being disturbed by
them. No doubt, however, the conviction has grown
with each step in our progress that the principles we
have learned must cause us to readjust our views of the
highest elements in human thought to a degree that
must be inversely proportional to our previous acquaint-

278

EVOLUTION AND THE HIGHER HUMAN LIFE 279

ance with the laws and processes of nature. But the
seeker after truth is fearless of consequences. He knows
that truth cannot contradict itself; and if those to
whom he looks for authority give him conflicting ac-
counts of nature's history, he knows that one of these
must be less surely grounded than the other. The
investigator soon learns to withhold final judgment,
realizing that the primary conditions for intellectual
development are the plasticity and openness of mind that
dogmatism and finality destroy. He knows that while
his researches may be, and indeed must be, iconoclastic,
they provide him with better icons in place of the old.

Let us recall the steps in our progress through one and
another field of knowledge, from which representative
facts have been chosen for classification and summary.
We began with the basic principles of organic structure
and workings, and then we examined serially the larger
categories of the evidences relating to evolution as a
fact, and to the mode of its accomplishment by natural
factors. Proceeding to the special case of our own
species, we learned that human beings are inevitably a
part of nature and not outside it ; in structure, develop-
ment, and palseontological history, mankind is subject to
the control of the uniform laws which operate through-
out the entire range of living things. Finally, the men-
tal characters and the social relations of human organ-
isms were derived from beginnings lower down in the
scale, and were proved to be no more exceptional than
the physical constitution of a single human being.

Are we to forget all of these things when we try to put
in order our ideas belonging to the categories of higher
thought? Can we hope to find the truth if we fail to

280 DOCTRINE OF EVOLUTION

employ the methods of scientific common-sense which
only yield sure results? It is no more justifiable to
discard our hard-earned knowledge than it would be for
an advocate to undertake the conduct of a case in delib-
erate disregard of what he had learned of the law, or for
a surgeon to leave his knowledge at the door when he
entered the operating room. Too often we are bidden
to view the larger conceptions of nature and super-
nature as something outside the realm of ordered knowl-
edge; too frequently we are given statements upon
authority that takes no account of reason, and we are
asked to accept these views whether or not they accord
with the demonstrated facts of common-sense. But
those who have followed the present description of evo-
lution can readily recognize their obligation to use for the
further analysis of higher human life the means which
have given in that doctrine the most reasonable explana-
tion of the natural phenomena already investigated.

I need hardly say that we now enter upon the most
difficult stage of our progress. The regions we have
traversed were more readily explored because they were
remote from the matters now before us ; even in the case
of man's mental and social evolution it was possible to
take a partially impersonal view of certain of the essen-
tial elements in human life, which we cannot do now.
For ethics and religion and philosophy are groups of ideas
that are familiar to us as the property of mankind alone.
Countless obstacles are in the way. Much mental inertia
must be overcome, for it is far easier to accept the aver-
age and traditional judgments of other men — to let well
enough alone — than it is to win our own way to the
heights from which we may survey knowledge more fully.

EVOLUTION AND THE HIGHER HUMAN LIFE 281

Human prejudices confront us as a veritable jungle,
hemming us in and obstructing our vision on all sides ;
and perhaps much underbrush must be cut away if we
are to see widely and wisely. Nevertheless, to those
imbued with a desire to learn truth, anything and every-
thing gained must surely repay a thousand times all
efforts to obtain clearness of vision and breadth of view.
With our perspective thus rectified by our backward
glance, we turn to the three divisions of human thought
now to be examined. The conceptions of ethics come
first for reasons that must be apparent from the classifi-
cation of the facts of social evolution; just as mental
attributes and communal organization are inseparable,
so rules of conduct arise pari passu with the origin of a
biological association. Religion and theology form the
second division, which takes its origin in part from
the first, for these two groups of ideas are largely con-
cerned with the authority for right conduct and with
human responsibihty for taking the right attitude to-
ward the entire visible and unseen universe. Finally,
science and philosophy are briefly treated as evolved
products which include within their scope all that there
is in human knowledge ; for this reason they take the
highest place, instead of the position below religion usu-
ally assigned to them. At the last, having reached our
final standing ground, we must look back in order that
we may clearly define the lessons and ultimate values
of the whole doctrine of evolution.

Ethics is the science of duty. It is usually restricted
to an examination of purely human obligations, and to

282 DOCTRINE OF EVOLUTION

a search for the reasons why men should do certain
things and refrain from committing other acts. Like
psychology and sociology, ethics began as a strictly
formal and a "priori system of dogmas which related to
the life of cultured human beings alone. Again, like
the sciences specified, it gradually broadened its scope
so as to include the conventions of races lower in the
scale than the civilized peoples who only were sufficiently
advanced intellectually to conceive it. Thus the com-
parative method came to be employed, and in direct
proportion to its use, more liberal views have developed
regarding the diverse methods of thought and standards
of social life and of conduct among differently condi-
tioned peoples. Still more important is the demonstra-
tion that human ethics as a whole, like human faculty
and civilization, takes its place at the end of a scale
whose beginnings can be found in lower organic nature.
Those who have followed the account of social evo-
lution given in the preceding chapter must realize that
the basic general principles of natural ethics, as con-
trasted with '^formal" ethics, have already been dis-
covered and formulated. A biological association of
whatever grade and degree of complexity is impossible
unless biological duties are discharged. Human ethical
conduct differs from insect and protozoon ethical con-
duct only in the element of a participation in the pro-
cess by the explicit consciousness of man that he has
definite obligations to others; and this distinguishing
characteristic is the direct outcome of an evolution
which adds reflection and conceptual thought to a men-
tal framework derived from prehuman ancestors. The
insect hurries about in its daily life as an animated

EVOLUTION AND THE HIGHER HUMAN LIFE 283

machine, whose activities are defined by heredity;
its special mode of conduct is just what nature has pro-
duced by selection from among countless other forms
of living which have not had the same degree of biologi-
cal utility. But man alone recognizes vaguely or clearly
the ^^why and wherefore" of his acts that are far more
instinctive than he supposes; he only is consciously
aware of the bonds of Idnship and economic interdepen-
dence. He looks about for the authority which imposes
his duties and fashions his bonds, and conceives this
authority as something superhuman, until the com-
parative studies of evolutionary phenomena reveal the
true causes in uniform nature itself.

According to biological ethics, the fundamental obli-
gations of all living things are the same, even though
the modes of discharging them may be various. Every
individual must lead an efficient personal life by pro-
curing food, but animals differ very much in their ali-
mentary apparatus ; among other things they must re-
spire, but some are so simply organized that they do not
need elaborate organs like the tufted gills of a crusta-
cean or the lungs of higher vertebrates. Every in-
dividual of whatever grade must also provide in some
way for the maintenance of the species, but some, like
a conger eel, produce enormous numbers of eggs which
are left uncared for, while others, like birds, bring forth
only a few young, which receive constant attention and
protection until they are able to shift for themselves.
Nature has no place for even a human community un-
less individual and racial interests are conserved, so
that the greatest duties are definitely formulated — all
else is secondary and less essential. Selfish action on

284 DOCTRINE OF EVOLUTION

the part of every unit is obligatory, but it must always
be antecedent to endeavor in the wider interests of the
race if the unit is a solitary individual ; if it is a member
of an association of any grade, then it must serve its
fellows in some way. Egoism and altruism are natural
essential guides to conduct ; neither can safely exclude
the other, and their antithesis sets a problem for every
organism, which is to work out the proper compromise
that will be most satisfactory to nature. The Golden
Rule is taught by biology because it is demonstrated
empirically, and not because it has any a priori value as
an ideal ethical principle.

But utilitarian or natural ethics need not stop with
the statement of vague generalities like the foregoing.
In human society, as in the life of low animals, the worth
and value of any form of conduct and of every single act
can be estimated by definite biological criteria. The
institution of marriage and the conventions of common
morality have their biological value in their provision
for the care of children; the safeguards of property
rights enable the industrious — the biologically effi-
cient — to keep the fruits of their labors ; the establish-
ment of formal civil and criminal laws is biologically
valuable in a social way, in so far as such laws diminish
the unsettling effects of personal animosity and the
desire to wreak personal vengeance ; the establishment
and differentiation of legislative, executive, and judicial
organs of government lead to greater social solidarity
and higher biological efficiency. Thus unchecked in-
dividualism is just as wrong ethically and biologically
among men as it would be in the case of insect communi-
ties, as pointed out in the preceding chapter ; no one has

EVOLUTION AND THE HIGHER HUMAN LIFE 285

a right to expect service or deference to personal inter-
est from others if he fails to work for them and for the
good of all. It is true that the social structure will stand
a great amount of tension, but if this becomes too great,
either a readjustment is effected, as when King John was
forced by the barons to concede their rights, or else the
whole nation suffers, owing to the selfishness of a few.
In the war between Russia and Japan, the latter won
because the individual soldier merged his individuality
in the larger mechanism of the regiment and brigade
and army corps, gladly sacrificing his life for the nation
represented by the person of its Emperor. The single
Russian soldier may have been far superior to a Japanese
in muscular strength, and perhaps in arms also, but
selfishness and greed on the part of many who were re-
sponsible for the organization and equipment of the
Russian armies rendered the whole fighting machine
less coherent and therefore less efficient than that of
the Japanese.

In the evolution of ethics the recognition of ideals of
conduct has followed long after the institution of a par-
ticular precept by nature, which is obeyed instinctively
and mechanically by force of inheritance. In the case
of the communities of insects, the results are the same
as though the individual animal fully recognized the
value of concerted endeavor. So among primitive
savages of to-day there is only a vague conception of
abstract duty as such, or it may be practically lacking,
as in the case of the Fuegians. So also a growing child
is substantially egoistic, and it must be taught by pre-
cept and example that the rights of others can be safe-
guarded only by the altruistic correction of personal

286 DOCTRINE OF EVOLUTION

action, long before the child can grasp the higher con-
ceptions of ethics. If a human being i;iever learns to do
so, and becomes a criminal through force of heredity or
circumstances, the machinery of the law automatically
comes into operation to conserve the welfare of the com-
munity. Such a criminal may be unable to control his
destiny, and may not be responsible for being what he is,
but nevertheless he must pay the penalty for his un-
social heritage by suffering elimination.

Ethical systems are built around man's vague recog-
nition of certain natural obligations, and they have thus
become more or less complex, and more or less varied as
worked out by different peoples. They must necessa-
rily be much concerned with social questions, with
morals in the usual sense and the more rigid principles
enacted into the spoken and printed law, but they have
also become closely connected with religion and theo-
logical elements. Especially is this true in the ethics of
barbarous and savage peoples, who accredit the '^cate-
gorical imperative" to some supernatural power, as we
are to see in a later section. The one point that comes
out clearly is that the systems of conduct and duties
have evolved so as to be very different among various
races, and that in the history of any one people, ethics
has passed through many varied conditions. What
may be deemed right at one period becomes wrong at
another when conditions may be changed ; in medieval
England the penalty of death was prescribed for one who
killed a king's deer, as well as for a highway murderer.
The Fijian of a quarter century ago killed his parents
when they became too old to be effective members of
their tribe. And so deeply ingrained was this principle

EVOLUTION AND THE HIGHER HUMAN LIFE 287

of duty that elderly people would voluntarily go to a
living grave surrounded by their friends ; while in other
authentic cases, parents have first killed their sons who
failed to obey the tribal law, and have then committed
suicide. We can see how nature and necessity would
institute a law requiring such conduct where a tribe must
carry on almost incessant warfare and where the avail-
able food supplies would be enough for only the most
efficient individuals. Infanticide also has been prac-
tised for reasons of biological utility, as among the
Romans, who at first maintained their racial vigor by
deliberately ordering the death of weak babes. But times
have changed, and ethics has become very different
with passing decades. Our civilization has resulted in
a development of human sympathy as an emotional out-
growth of necessary altruism ; this motive directs us
through charitable institutions and hospitals to prolong
countless lives which are more or less inefficient, but
which do not render the whole body politic incompe-
tent in its struggle for existence.

Nature then has itself attended to the development
and institution of ethics. As we look back over the
long series of stages leading to our own system of con-
duct the most striking feature of the history is the in-
creasing power of self-control or inhibition. As a natu-
ral instinct this tends to prevent the committing of acts
which for one reason or another are naturally harmful to
society as a whole. What we call conscience is an in-
stinct implanted by purely natural factors, and it un-
consciously turns the course of human action in the
directions of selfish and altruistic interests. Conscience,
then, without ceasing to have validity and efficiency, ap-

288 DOCTRINE OF EVOLUTION

pears on the same plane with all of the other products
of evolution which owe their existence to individual or
social utility.

Theology and religion involve intimately related con-
ceptions of the world, its make-up, and its causes.
Strictly speaking, religion is a system of piety and wor-
ship, while theology deals more particularly with the
ultimate and supernatural powers conceived in one
way or another as the God and the gods who have con-
structed the universe and have subsequently ordered
its happenings. A religion is a group of ideas having the
effect of motives ; it is dynamic and directs human con-
duct. Theology, on the other hand, is more theoretical
and descriptive, and its conceptions, together with
those of other departments of human thought, give the
materials for the formulation of the religious beliefs
which determine the attitudes of men toward all of the
great universe in which they play their part and whose
mysteries they attempt to solve.

Defined and distinguished in these ways, these two
departments of higher human life present themselves
for comparative study and historic explanation. They
differ much among the varied races of mankind, so
much, indeed, that an investigator who approaches
their study with a knowledge only of Christian religion
and theology finds it difficult at first to recognize that
the same fundamental ideas, although of far cruder
nature, enter into the conceptions of an idol-worshiping
fanatic living in the heart of Africa. But, neverthe-
less, beliefs that fall within the scope of the definitions

EVOLUTION AND THE HIGHER HUMAN LIFE 289

adopted above are to be found among all men, and they
must be examined so that their agreements and differ-
ences may be demonstrated, and their common elements
may be explained as the natural products of a process of
evolution.

Such a broad comparative study, like that of physical,
mental, and social phenomena discussed heretofore,
must be conducted objectively; that is, each and every
particular belief of a religious or theological nature
which can be discovered in any race is entitled to a place
in the array of materials which demand scientific treat-
ment. They must be verified, classified, and summa-
rized, in order that their total meaning and value can
be discovered. It must be strongly emphasized that for
such purposes the inherent validity and truth or falsity
of diverse religions are not called into question when
they are so considered as objects of study; many still
entertain the view that the mere task of conducting an
analysis of a group of religious beliefs of whatever nature
must tend to destroy or alter that system of religion in
some way and degree. But whatever the comparative
student may himself believe, the conception of Jehovah
in the Hebrew religion is quite as legitimate an object of
study as the Buddhistic concept of Brahma as the Ulti-
mate Being, or the Polynesian idea of Tangaroa as the
god of the waves. We would naturally be inclined to
exclude the last from our own personal system of piety
and worship as the childish concept of an imaginative,
adolescent race; but whatever the truth may be, the
fact of a belief in Tangaroa is as real as the fact of Chris-
tian belief in God. We can no more destroy any one
of these ideas by investigating its nature and origin than

290 DOCTRINE OF EVOLUTION

we destroy the efficacy of the human arm when we study
its muscles and bones and sinews. The former, like the
latter, take their places among natural phenomena whose
history must be inquired into if there are any reasons for
supposing that they fall within the scope of evolution.
I would be the last to lead or to take part in an attack
upon any system of religion, but as a student who is in-
terested in the universality of organic evolution, I am
forced to scrutinize each and every authentic account
of a religion to see if such systems present objective evi-
dence of the fact of their evolution through the opera-
tion of purely natural causes.

But before passing to a detailed treatment of the anal-
ysis, synthesis, and genesis of religious systems, let us em-
ploy our common-sense for a brief backward glance over
the known history of familiar facts. Every one is aware
that the Christian religions of our time and community
have not existed forever ; this, indeed, is indicated by the
way the passing years are denominated. We call the
present year 1907 Anno Domini, and this whole expres-
sion explicitly refers to the fact that less than two thou-
sand years ago the Christian systems of piety and wor-
ship collectively took their origin from their Hebrew
ancestor. The same parent has produced the relatively
unchanged Judaism of the present day. Judaism itself
evolved under the influence of the Prophets, of Moses,
and of Abraham. Turning to Asia, we learn how Bud-
dhism evolved from Brahmanism. The teachings of
Mohammed at a later time developed into the formu-
lated precepts of the Koran. Would any one venture to
assert that all or any of these systems of thought have
stood firm and immutable from the finite or infinite

EVOLUTION AND THE HIGHER HUMAN LIFE 291

beginnings of time ? Would any one contend that the
creeds of Protestantism have remained unchanged even
during the past twenty years ? Like all departments of
human belief and knowledge, religious concepts have
obviously altered in natural adjustment to changing
times and to advancing conditions of human intellect ;
and the question turns to the mode by which they have
been modified, to see whether natural causes of evolu-
tion have changed them, and have originated their
earliest beginnings at the very outset of human history.
It has been stated above that every race of mankind,
however primitive or advanced it may be, holds some
form of religious belief based upon some conception of
the supernatural powers back of the world ; and what
the universe is conceived to be must largely determine
the particular characteristics of a theology, and through
this the special form of its attendant religion. We
have before us a wide array of types to study and to
compare, which vary so greatly, partly for the reason
specified, that an inclusive definition of religion must be
couched in very general terms. If we define it as the
attitude and reaction of a human being conditioned by
his knowledge of the immediate materials and his con-
ception of the ultimate powers of the universe, its scope
is so extended as to include the ideas of the atheists and
agnostics as well as the crude conceptions of lower races
and those systems of piety and worship conventionally
regarded as religions by civilized peoples. More than
this : we cannot regard the total reaction of a thinking
being as essentially different in ultimate value from the
attitudes toward their worlds of animals lower than man.
The situation of a well-trained sheep dog is one of pas-

292 DOCTRINE OF EVOLUTION

tures and fences and gates, of rain and sunshine, of
sheep, and of a master whose voice is to be obeyed.
What the dog may do is partly determined by what it
finds in its world of animate and inanimate things. Al-
though the animal's ^^ conception" of such things must
be far simpler than a human being's, nevertheless its
life is lived in reaction to all of its surroundings as they
are presented to its cerebral apparatus by the proper
organs. So in the human case, conduct is directly af-
fected by the living and lifeless objects of a total human
situation, the only difference being that reflective con-
sciousness and reasoned interpretation have their share
in determining the assumed attitude in ways that seem
to have no counterparts as such in the mental lives of
lower animals. But whether or not the similarity be-
tween human religion and lower organic reaction be
admitted, — and the admission is one that greatly facili-
tates an understanding of evolution in this field, — the
general resemblance of all religions in fundamental
character at least must be accepted.

Another general feature of religious systems is their
complexity. The essential elements of all of them are
few indeed, as we shall see at a later point; they are
beliefs regarding ultimate powers, human responsibil-
ity to such powers, and future existence. These have
taken one specific form or another in various lines of
racial evolution, but aside from their own changes they
have gathered about them many other articles of creed
relating to other departments of thought and life. Ethi-
cal rules of conduct are so added, as in the Hebrew
religion where the idea of Jehovah involves God the
Euler and Judge who imposes and administers the laws

EVOLUTION AND THE HIGHER HUMAN LIFE 293

of right living. Social customs are almost invariably-
intertwined with religious views, among savages as well
as among the more advanced Mohammedans whose
rules relating to family organization form an integral
part of the whole cult. The emotional elements play a
large part in some cases, in the fanatical creeds of the
Dervish and Mahdist and in the '^revivals" under nearer
observation. In Greek cosmology and worship, aesthet-
ics figured to a large degree. Temperamental and
other psychological characteristics have profound effects
upon religions, which we may illustrate by such extreme
examples as the austerities of New England and Scotch
Presbyterianism and the contrasted liberties of the
natural religions of tropical races. But all of these ac-
cessory elements belong to other well-defined depart-
ments, some of which have already been considered,
and among the materials of their proper divisions they
find their interpretation and historical explanation in
evolution. It is with the basic elements themselves
that we are now concerned.

Only within recent years have systematic attempts
been made to classify religions on the basis of impersonal
objective study. Throughout all times men have in-
stinctively set up their own religion as the only true one,
besides which all others are designated simply as false —
a very natural distinction, but one which is too naive for
science, as well as one that takes into account subjec-
tive or personal values which are not to be considered
in an objective comparison and analysis. The linguis-
tic basis was first employed by Mtiller, with the result
that religions were placed in the category of evolution-
ary accompaniments of the other mental possessions

294 DOCTRINE OF EVOLUTION

and of the physical quahties of genetically connected
peoples. Thus the nations of Europe that branched out
in all directions from very nearly the same sources
possessed common linguistic characters and somewhat
similar creeds. The Sanskrit-speaking races were the
original Brahmins and Buddhists. Ancestor worship is
an accompaniment of the peculiar languages spoken by
eastern Mongolian peoples. And although the correla-
tion specified is by no means invariable, because a race
of one stock can readily accept the religion of a neighbor
or of a conqueror, yet much is gained through the in-
troduction of the idea of evolutionary relationships.

A more logical classification frankly adopts the genetic
method and clearly recognizes the direct effects of cultu-
ral and intellectual attainments upon the w^ay a reli-
gious system becomes formulated. In such an arrange-
ment, similar to that of Jastrow, religions can be classed
as those of savagery, of barbarism, of advanced culture,
and of civilization. Among the first named, nota-
bly those of Polynesian and African tribes, beliefs in
diversified ghosts and spirits bulk largely, and every
moving thing, be it a river or a cloud or a tree or animal,
is held to be animated by an invisible conscious genius ;
the spirits reside in everything, as well as in the great
unknown beyond. Above these in the scale are the
religions of so-called primitive cults, more elaborate and
formalized in the ancient beliefs of Egypt and Assyria,
but still below those of advanced culture, which make up
a third group. The fourth class includes the religions
which tend to be coextensive with life, and which enjoin
the higher harmony of practical and theoretical con-
ceptions. Taking Christianity as an example, the con-

EVOLUTION AND THE HIGHER HUMAN LIFE 295

trast with the behefs of savagery brings out clearly the
nature of progressive development. Here religious
thought is no longer esoteric, confined to a chosen sect
like the Levites among the Hebrews or the shaman and
medicine-man among the American Indians ; nor is
religious observance restricted to the innermost shrine
of the tabernacle or sacred dwelling, accessible to few or
only one. It comes to be regarded as something in
which each and every individual can participate, and
a personal possession that has a direct part in determin-
ing all forms of human life and action. This is another
way of saying that the more highly evolved religions
owe their character to the greatly varied and abundant
intellectual elements which are built into them. And
this is why religion in the highest form, more clearly than
in the lowest forms, is to be spoken of as an outlook upon
the world which is determined by the total intellectual
equipment of the individual man who thinks about the
universe and directs his course of action by what he finds.

We come now to a closer concrete study of the basic
elements of religion ; that is, of those behefs that are in-
variably present, in one form or another, in every system
of piety and worship, and that constitute the innermost
framework beneath the secondary creeds added to
them. Following Mallock and others, we may dis-
tinguish three such elemental conceptions. These are,
first, the behef in the existence of a supernatural being
or beings, endowed with intelligence like, but superior to,
our own; second, the idea of human responsibility to
this or these powers ; and, third, the behef in immortality

296 DOCTRINE OF EVOLUTION

as an attribute of the supreme powers and of human in-
dividuals also. Let us see how these beliefs appear in
characteristic systems of religion.

In all forms of Christianity the central idea is the con-
ception of a triple unity personified as God. He is re-
garded as the Creator who has made all things and who
demands reverence from his subjects. He is the Author
and Finisher of the faith as well as the sole Cause of the
universe itself. Much of this element is directly derived
from Judaism, the progenitor of Christianity ; but a dif-
ference consists in the triple nature of the supreme being
according to the newer creed. As the original and su-
preme being, God is not only the Creator, but the watch-
ful Judge as well, demanding reverent obedience to the
laws of the world in which he has placed man, and im-
posing sacrifices and penitential observances when his
mandates have been disobeyed. As the God of Mercy
he is incarnated in the person of Jesus of Nazareth, and
offered as a vicarious sacrifice for sinners who are thus
enabled to escape the penalties they would otherwise
have suffered. As the Holy Ghost, God is the vaguely
personified ultimate source of the higher and nobler
elements of human thought, aspiration, and life in gen-
eral. The second basic tenet of Christianity is that of
human responsibility to God, to whom man is related
as the created to a creator, as a subject to a ruler, and as
one saved to his redeemer. The institutions of sacrifice
and ritual are outward signs of human subjection to God
himself and to his laws, according to which the universe
is conceived to operate. Finally, Christianity teaches
that just as God in his single and triune form is eternal,
so the soul of man is immortal, with or without its

EVOLUTION AND THE HIGHER HUMAN LIFE 297

earthly temple of flesh and blood. The essential think-
ing individual is believed to pass to heaven, where
rewards for right living are bestowed, or to hell, in order
to suffer punishment for sin during all eternity, or some
part of it, according to different views regarding the effi-
cacy of Christ's vicarious atonement.

It is true that the manifold sects of Christianity differ
somewhat in the detailed forms of these three essential
beliefs, but not to the same degree as in the case of the
secondary additions. God's laws, Christ's teachings,
and the inspiration of the Holy Ghost are the recognized
guides to conduct ; but human frailty has been such that
the history of Europe presents a panorama of warring
sects in almost unceasing strife about details of ritual and
interpretation, while the great fundamental truths have
been too frequently ignored. The conflicts of Catholics
and Protestants, Puritan and Cavalier, and Northern
and Southern Presbyterianism, have not been waged on
account of basic beliefs like the three outlined above, or
about the Golden Rule, but on account of comparatively
trivial details which to the impersonal student have
scarcely more than the value of individual preference.

Judaism, the next great religion, has already been
mentioned as the parent of Christianity, to which it gave
the concept of a Supreme Being, as well as that of a Mes-
siah. It is a purer monotheism than its outgrowth,
whose trinity is more like certain elements of Greek
theology. Jehovah is the one supernatural power, the
creator and lawgiver and immediate cause of all the
workings of nature. It is he who shapes the world out
of nothingness and who separates the waters from the
dry land ; he parts the waters of the Red Sea to save

298 DOCTRINE OF EVOLUTION

the Israelites, and brings them together again to over-
whelm the pm'suing hosts of Pharaoh. It is his voice
that thunders from Mt. Sinai, and his finger that traces
the commandments to rule the lives of his chosen people
upon the tablets of stone intrusted to Moses the Seer.
At the behest of Joshua he holds the sun and the moon in
their courses above the vale of Ajalon so that there will
be more time for the destruction of the Philistines. In
brief, Jehovah is the eternal god of law and power, de-
manding sacrifice and priestly atonement, and promis-
ing happiness eternal upon the bosom of Abraham to
those who recognize their responsibility to him and
obey his precepts. Again, there are three fundamental
beliefs, that differ from those of Christianity as the
Talmud diverges from the New Testament scriptures.

Mohammedanism is another outgrowth from this
group of religions. The teachings of the Koran give the
institutional and ritual forms to the same three elements
distinguished above. God is the identical single God ;
and Mohammed is His Prophet, as Jesus is the New
Prophet of Christendom. The true believer's responsi-
bility entails active warfare upon the heretics, that is,
those who do not accept the Koran. The immortal
state of Mohammedanism is a very different thing from
the heavenly bliss of Christianity, for the promised
rewards are such as would appeal to the warm-blooded
Southern temperament.

Turning now to Asia, we find in Brahmanism and Bud-
dhism two systems of religion that are related to one
another exactly as are Judaism and Christianity. The
analogue of the Old Testament is a group of priestly
hymnal writings known as the Vedas, which date back

EVOLUTION AND THE HIGHER HUMAN LIFE 299

to about the fourteenth century before Christ Uved.
Their objects of worship at first are numerous invisible
beings that actuate the things of the world, as in Greek
theology, but later one of them assumes preeminence as the
all-pervading essence of things, — Brahma. The precepts
of Brahmanism enjoined adoration of the unseen powers
and of their works, as well as practical rules of human
conduct, such as those which divided a man's life into
the four periods when he should be successively a student,
the head of a family, a counselor, and a religious men-
dicant who should renounce the world of social activities
and human desires. In earlier writings, the immortal
state is a kind of heaven, but later it meant simply an
absorption into Brahma, the eternal impersonal being.
Buddha was an orthodox Brahman reformer of the
sixth century before our present era, just as Jesus was an
orthodox Hebrew reformer. The essential creed of
Buddha made his religion far more ethical than earlier
forms, and placed it on a plane even above Christianity
of later centuries. This creed relates to the element of
human responsibility particularly, the other two remain-
ing much as they were found by Buddha. According
to his teachings, a man rested under an obligation to live
nobly in the truest sense, and he acquired merit —
karma — or lost it, in proportion to his deserts. At
death a human soul is reincarnated, in a lower form of
animal or even in a being residing in one of a series of un-
seen hells, if punishment is due ; if a higher state is mer-
ited, progress is made through thousands of existences
until perfection is rewarded by an eternal fusion with
the essence of Brahma. It is because there is no escape
from just punishment that Buddhism in its original form

300 DOCTRINE OF EVOLUTION

is properly denoted more ethical than a religion which
teaches that sacrifice of any kind will exempt the sinner
from deserved penalties and bring about the bestowal of
unearned rewards.

Polytheism is the name given to a religion such as that
of the Greeks or Romans, who believed in many gods
and spirits of greater and lesser power. These super-
natural beings, each in its own sphere, immediately
directed the processes of nature and controlled the lives
of men. One of them, Zeus, was regarded as the su-
preme ^^ father of gods and men," who delegated specific
duties to others ; Ares was the god of battles, Hermes
was the messenger, Athena implanted wisdom in the
minds of men, and Poseidon ruled the sea. The gods
were very human to the Greek mind, hving in Olympus as
men do upon earth, and even visiting the mortals. Their
worship involved propitiatory sacrifices and rites as well as
thanksgiving offerings when favors were bestowed. But
although they were immortal, they did not allow the im-
mortal souls of human beings to j oin them in their elysium,
but compelled the disembodied shades to wander un-
happily among the tombs and about their earthly abodes.

Roman theology and religion comprise almost identi-
cal forms of the three fundamental elements. The names
are changed, and Zeus becomes Jove, his wife Hera
is Juno, Ares is Mars, and Hermes is called Mercury.
In all other respects, however, the two systems are as
much alike as the Greek and Roman languages and
Greek and Roman physique.

The religions of savagery are far less analytical, and
much more naive in their reference of natural happen-
ings to the direct interposition of malevolent and be-

EVOLUTION AND THE HIGHER HUMAN LIFE 301

nevolent spirits. Their gods are numerous as in Greek
religion, and likewise one of them is usually set up as the
superior deity, to be the Tirawa of the Indian, the
greater Atua of Polynesia, and the Mumbo Jumbo of a
West African negro. There is no centralization of the
supernatural powers, as in the Jehovah of Judaism and
the still subtler Brahma of the Asian. Then, too, the
gods must be concretely materialized for purposes of
worship and sacrifice ; consequently idols are made, to
be regarded as the actual spirits themselves permanently
or for the time being, and not viewed as representations
of an ideal, like the statues of more advanced peoples.
The immortal state is described in low religions in
various ways that seem to be determined by what the
believer himself most desires. The spirit of an Ameri-
can Indian goes to the happy hunting-grounds, where it
mounts a spirit pony and forever pursues the ghosts
of bison which it kills with spirit bow and arrows ; to
provide these necessaries his earthly possessions are laid
beside his dead body. The Norseman was conducted
to Valhalla and, attended by the Valkyrie as hand-
maidens, he eternally drank mead from the skull of an
enemy and gloried over his mundane prowess in battle.
It is unnecessary to expand the foregoing hst, because
the examples sufficiently represent the various grades
of human religions. Regarding them as typical, we can
see how universal are the three fundamental ideas with
which we are concerned. Every race has its own con-
ception of future bliss, as well as its conception of respon-
sibility to the immortal and supernatural powers of the
universe. Whatever may be the actual reality, and
however closely the conceptions of one or another re-

302 DOCTRINE OF EVOLUTION

ligion may approximate to the truth, such reality and
approximation are not the subjects of the present discus-
sion. Nor is it our purpose to bring out more exphcitly
the genetic relationship of one religion to another ; the
evolution of Buddhism from Brahmanism, the origin
of Christianity from Judaism, and the divergent de-
velopment of the several creeds of Christendom amply
illustrate the nature of religious history. It is evolu-
tion here as elsewhere and everywhere.

Having distinguished the three general elements of all
religions, beyond which everything else is of minor impor-
tance, we now turn to the question as to the natural origin
of these elements. Clearly they cannot arise independ-
ently, for the belief in supernatural and eternal spirits is
closely connected with the conception of an immortal soul.

The first is the conception of infinite personalities that
later become more or less merged into one supreme being.
This begins with the idea of the soul as the human ego,
conventionally regarded as something independent of
the material body during life and immortal after death.
The savage goes to sleep, and in his dreams he goes
upon journeys and battles strenuously with other men
and with beasts, only to find when he awakes that his
body is not fatigued, and that it has not really taken
part in the activities of his dream life. His companions
about the fire also tell him that this is so, while he is
equally sure that his essential self has been doing many
things during the interval of sleep. In his dream life he
finds himself joined by others whom he knows are dead.
He sees again even those whose bodies he may have as-

EVOLUTION AND THE HIGHER HUMAN LIFE 303

sisted in eating. His total world very soon comes to
have an unseen region which is the abode of ordinarily
invisible beings having the forms of men, with whom his
own dream person can associate ; this unseen sphere is
furnished also with ghostly counterparts of the trees and
rocks and waters with which he is familiar when he is
awake. Before long his soul or ghost or spirit is con-
ceived as something which possesses two qualities : it
can be disassociated from his body and enter the spirit-
world where it seems to defy all the laws of waking life,
for with the quickness of thought it visits neighboring
islands as readily as. it passes to the next hut ; and it
possesses immortality, for it is exactly like the persistent
spirit-individualities of those who have died before him.
The other cause for the development of the conception
of gods and God in the mind of the savage is the fact
that things have been made which neither he nor any
other man can make. He can dig a ditch, and make a
house, and fashion a canoe, and build ramparts of earth ;
but human power has obviously been insufficient to con-
struct rivers and mountains and forests and their deni-
zens. Mankind itself has certainly been made in some
way, for it exists. Because the savage cannot conceive
of things being made excepting as they are made by the
human hand, and because so much confronts him that is
beyond the power of human construction, he comes to
postulate the existence of man-like, but greater than
human, personalities, and as he cannot see them in the
light of day, they belong to the spirit-world to which
souls go. Imagination sometimes gives human outlines
to shadows among the moon-lit trees, so that elves and
pixies, nymphs and fairies, become established in the

304 DOCTRINE OF EVOLUTION

world as the primitive man conceives it. Larger tasks
are discharged by more important spirits, and every-
thing natural thus becomes animated by supernatural
beings. Thor was the god of thunder ; Freia the god-
dess of spring and vernal awakening ; Athena inspired
the minds of men. Venus and Aphrodite played their
special parts, also. But such powers as these, estab-
lished by the untutored mind, needed to be accounted
for, and so in the more advanced religions Jove and
Jupiter were created as the more ultimate causes, in
response to intellectual demands. By combining all
powers into one, God and Brahma are the results.

Thus in merest outline the conception of the infinite
personality works out its evolution. At all times,
among primitive and higher religions, the powers are
clothed with human forms, and gods are pictured as
men endowed with intellects and passions, and motives of
vengeance and benignity. Man cannot shape his postu-
lated deities save in such forms, with the possible excep-
tion of the most philosophical concept of all, Brahma.

The second fundamental belief, namely, in immortality,
owes its origin in greatest measure to the psychological
processes described above. Another potent factor, how-
ever, has been the natural desire to continue existence
hereafter, usually in order to reap rewards not bestowed
here. This desire is implanted by nature through the
operation of purely biological factors, and it has the
value of an organic instinct. To specify more particu-
larly, nature has placed every organic individual under
the necessity of doing its utmost to prolong its own life
in the interests of itself, of others of its tribe, and of its
species. Extinction is not faced willingly by a human

EVOLUTION AND THE HIGHER HUMAN LIFE 305

being endowed with full consciousness any more than it
is passively tolerated by a lower animal which instinc-
tively struggles with its foes until death. So the desire
to continue alive — the '^ will to live'^ — is a natural in-
stinct, which combines wdth the belief in persistent dis-
embodied spirits and, no doubt, with many other ele-
ments, to develop the basic conception of some kind of
an immortal existence.

The third element, human responsibility to the infinite
personality, is variously recorded in lower and higher
religions. Its conception grows partly out of the feel-
ings of awe and terror inspired by great works of nature
such as the thunder-storm, the cyclone, and the volcano,
while the orderly and regular workings of even everyday
nature seem to demonstrate the direct control of the
powers who rule man as well. The savage sees his crops
destroyed by a tempest or drought ; he attributes the
disaster to the particular powers concerned with such
things whom he must have angered unwittingly, and
whom he must propitiate by sacrifice or penitence.
His individual and tribal acts do not always accomphsh
the desired ends, and again the laws of infinite and ulti-
mate powers must have been contravened, as he inter-
prets the situation. Therefore his whole rehgious con-
sciousness was exerted in the direction of finding out
what was the ultimate constitution of nature, with
which human activities must harmonize if they are to be
successful. Bound by custom and convention and bio-
logical law, he looks about wonderingly to find the exter-
nal authority for his bonds. To his mind this authority
must be the host of spirits and gods who had made him
and the things of his world. It is in this way that so many

306 DOCTRINE OF EVOLUTION

ethical elements have found places in religious doctrines,
to be viev/ed as absolute rules of conduct coming from
outside of nature, and not from nature itself, in the way
the earlier sections of this chapter have shown.

Let us now summarize the results of the foregoing
brief survey, conducted by the identical methods em-
ployed for the analysis of other bodies of fact. We
have sought for those characteristics which are common
to all religions of whatever time and place and race.
Combined with many secondary and adventitious ele-
ments of other fields of thought and action, such as social,
political, ethical, and psychological factors, they have
proved to be the three essential beliefs in God or gods,
human responsibility, and immortality. As a veritable
backbone, they underlie and support the whole body
of religious doctrine and organs of thought formed about
them. We have seen, furthermore, that a natural ex-
planation of the way these elements have originated can
be discovered by the comparative student of religion,
who describes also how they have variously evolved
among different peoples. In all of this we have not
questioned at any time the validity or reality of any one
of these concepts ; to ask whether or not they corre-
spond actually to the truth is beyond our purpose, which
is simply and solely to inquire whether even these mental
conceptions furnish evidence of their evolution in the
course of time. I believe that such evidence is found,
and I believe also that this discovery must be of the
greatest importance to everyone in formulating a system
of religious belief, but the construction of this is not the
task of science as such. Every individual must work
out his own relation to the world on the basis of knowl-

EVOLUTION AND THE HIGHER HUMAN LIFE 307

edge as complete as he can make it, but every individual
must accomplish this end for himself. Because no two
men can be exactly alike in temperament, intellect, and
social situation, it is impossible for entire agreement in
religious faith to exist. One's outlook upon the whole
universe is and must be an individual matter; science
and evolution are of overwhelming value, not by direct-
ing the mind to adopt this or that attitude toward the
unseen, but by providing the seeker after the truth with
definite knowledge about the things of the world, so that
his position may be taken on the sound basis of reason-
able and common-sensible principles.

When we take up science and philosophy, or knowl-
edge as a whole, after religion, it may seem that we have
reversed the proper sequence. There are many reasons
for following this course, inasmuch as ^'knowledge" is
the all-inclusive category of thought ; our world is after
all a world of individual consciousness and ideas. In
dealing with religion, ethics, social organization, and hu-
man culture, we have been concerned with the evolu-
tion of so many departments of thought and action;
and now we are to develop a final conception of evolution
as a universal process in the progress of all knowledge.

Let us look back over the history of mathematics.
The primitive human individual did not need to count.
He dealt with things as he met them, and he disposed
of them singly and individually. A squirrel does not
count the nuts it gathers ; it simply accumulates a store,
and it perishes or survives according to its instinctive
ability to do this. Just so was primitive man. The

308 DOCTRINE OF EVOLUTION

savage, when he organized the first formed tribes, learned
to count the days of a journey and the numbers engaged
on opposite sides in battle. He employed the ^ ' score '^
of his fingers and toes, and our use of this very word is a
survival of such a primitive method of counting. The
abacus of the Roman and Chinese extended the scope
of simple mathematical operations as it employed more
symbohc elements. With the development of Arabic
notation capable of indefinite expansion, the science
progressed rapidly, and in the course of long time it has
become the higher calculus of to-day. The conceptions
of geometry have likewise evolved until to-day mathe-
maticians speak of configurated bodies in fourth and
higher dimensions of space, which are beyond the powers
of perception, even though in a sense they exist concep-
tually. The behavior of geometrical examples in one
dimension leads to the characteristics of bodies in two
dimensions. Upon these facts are constructed the laws
of three-dimensional space which serve to carry mathe-
matical thought to the remoter conceptual spaces of
which we have spoken. It may seem that we are record-
ing only one phase of mental evolution, but in fact we are
deahng with a larger matter, namely, with the progres-
sive evolution of knowledge in the Kantian category of
number.

Natural science began with the savage^s rough classi-
fication of the things with which he dealt in everyday
life. As facts accumulated, lifeless objects were grouped
apart from living organisms, and in time two great divi-
sions of natural science took form. Physics, chemistry,
astronomy, geology, and the like describe the concrete
world of matter and energy, while the biological sciences

EVOLUTION AND THE HIGHER HUMAN LIFE 309

deal with the structure, development, interrelation-
ships, and vital activities of animals and plants. Surely
knowledge has evolved with the advance in all of these
subjects from decade to decade and from year to year.
And just as surely must evolution continue, for the world
has not stopped developing, and therefore the great
principles of science must undergo further changes,
even though they are the best summaries that can be
formulated at the present time.

Philosophy deals with general conceptions of the uni-
verse. When we look back through the ages we find
men picturing the world as an aggregate of diverse and
uncorrected elements — earth, air, fire, and water. The
synthesis of facts and the construction of general prin-
ciples down through Bacon, Newton, and Schopenhauer
to modern world conceptions results in the unification of
all — ''the choir of heaven and furniture of earth.''
The lineal descendant of the long line of ancestral phi-
losophies is the monism which sees no difference between
the living and lifeless worlds save that of varying com-
binations of ultimate elements which are conceived as
uniform ''mind-stuff" everywhere. Whether or not
this universal conception of totality is true, remains for
the future to show. For us the important truth is that
here, as in all other departments of knowledge, evolution
proves to be real.

In closing the present description of the basis, nature,
and scope of the doctrine of evolution, I find great diffi-
culty in choosing the right words for a concise statement
of the larger values and results of this department of

310 DOCTRINE OF EVOLUTION

science. So much might be said, and yet it is not fitting
for the investigator to preach unduly. The lessons of
the doctrine must be brought home to each individual
through personal conviction. But because I firmly be-
lieve in the truth of the statement made in the opening
pages, namely, that science and its results are of prac-
tical human value, it is in a sense my duty as an advo-
cate of evolution to make this plain.

The method of science is justified of its fruits. At the
very beginning we learned how, and how only, sure
knowledge can be obtained and how it differs from a be-
lief which may or may not correspond with the'truth.
Based upon facts of smaller or larger groups, scientific
laws are so many summaries of past experience, and they
describe in concise conceptual shorthand the manifold
happenings of nature. Their difference from belief in-
heres in their ability to serve as guides for everyday and
future experience. This entire volume is a plea for the
employment of common-sense as we look upon and in-
terpret the world in which we have our places and in
which we must play our roles. Our search for truth will
be rewarded in so far as we organize our common-sense
observations into clear conceptions of the laws of na-
ture's order.

The doctrine of evolution enjoins us to learn the rules
of the great game of life which we must play, as science
reveals them to us. It is well to remember that a little
knowledge is a dangerous thing, but because evolution is
true always and everywhere, an understanding of its
workings in any department of thought and life clears
the vision of other realms of knowledge and action.
Perhaps the greatest lesson is at the same time the most

EVOLUTION AND THE HIGHER HUMAN LIFE 311

practical one. It is that, however much we may concern
ourselves with ultimate matters, our immediate duties
are here and now, and we cannot escape them without
giving up our right to a place in nature. We are taught
by science that we live under the control of certain funda-
mental biological, social, and ethical laws ; we might well
wish that they were otherwise, but having recognized
them we have no recourse save to obey them. Evolu-
tion as a complete doctrine commands every one to live
a life of service as full as hereditary endowments and
surrounding circumstances will permit. Thus we are
taught that the immediate problems of Hfe ought to con-
cern us more than questions as to the ultimate nature
of the universe and of existence.

Every one can find something worth while in the les-
sons of evolution, summarized in the foregoing state-
ments. The atheist, who declines to personify the ulti-
mate powers of the universe, may, nevertheless, find
direction for his life in the principles brought to light by
science. The agnostic, who doubts the validity of many
conventional dicta that may not seem well grounded,
can also find something to believe and to obey. Finally,
the orthodox theist of whatever creed may discover co-
gent reasons for many of his beliefs like the Golden Rule
previously accepted through convention ; and he must
surely welcome the fuller knowledge of their sound basis
in the materials and results of comparative analytical
study. To every one, then, science and evolution offer
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LECTURES ON SCIENCE, PHILOSOPHY, AND ART

A SERIES of twenty-one lectures descriptive in non-technical
language of the achievements in Science, Philosophy, and
Art, and indicating the present status of these subjects as concepts
of human knowledge, were delivered at Columbia University, during
the academic year 1907- 1908, by various professors chosen to repre-
sent the several departments of instruction.

MATHEMATICS — By Cassius Jackson Keyser, Adrain Professor of
Mathematics.

PHYSICS — By Ernest Fox Nichols, Professor of Experimental Physics.

ASTRONOMY — By Harold Jacoby, Rutherfurd Professor of Astronomy.

GEOLOGY — By James Furman Kemp, Professor of Geology.

BIOLOGY — By Edmund B. Wilson, Professor of Zoology.

PHYSIOLOGY — By Frederic S. Lee, Professor of Physiology.

BOTANY — By Herbert Maule Richards, Professor of Botany.

ZOOLOGY — By Henry E. Crampton, Professor of Zoology.

ANTHROPOLOGY — By Franz Boas, Professor of Anthropology.

ARCHAEOLOGY — By James Rignall Wheeler, Professor of Greek Ar-
chaeology and Art.

HISTORY — By James Harvey Robinson, Professor of Histor>'.

ECONOMICS — By Henry Rogers Seager, Professor of PoHtical Economy.

POLITICS — By Charles A. Beard, Adjunct Professor of Politics.

JURISPRUDENCE — By Munroe Smith, Professor of Roman Law and
Comparative Jurisprudence.

SOCIOLOGY — By Franklin Henry Geddings, Professor of Sociology.

PHILOSOPHY — By Nicholas Murray Butler, President of the University.

PSYCHOLOGY — By Robert S. Woodworth, Adjunct Professor of Psy-
chology.

METAPHYSICS — By Frederick J. E. Woodbridge, Johnsonian Professor
of Philosophy.

ETHICS — By John Dewey, Professor of Philosophy.

PHILOLOGY — By A. V. W. Jackson, Professor of Indo-Iranian Languages.

LITERATURE — By Harry Thurston Peck, Anthon Professor of the Latin
Language and Literature.

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POLITICAL PROBLEMS OF AMERICAN DEVELOPMENT. By

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CONSTITUTIONAL GOVERNMENT IN THE UNITED STATES.

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THE COST OF OUR NATIONAL GOVERNMENT. By Hexry
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THE BUSINESS OF CONGRESS. By Hon. Samuel W. McCall,
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THE PROBLEM OF MONOPOLY. By John Bates Clark, LL.D.,
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POWER. By Charles Edward Lucre, Ph.D., Professor of Me-
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THE DOCTRINE OF EVOLUTION. Its Basis and Scope. By Henry
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SOCIAL IDEALS IN MEDIEVAL STORY. By William Witherle
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JESUP LECTURES

LIGHT. By Richard C. Maclaurin, LL.D., Sc.D., President of the
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LECTURES ON SCIENCE, PHILOSOPHY, AND ART. A series
of twenty-one lectures descriptive in non-technical language of
the achievements in Science, Philosophy, and Art, and indicating
the present status of these subjects as concepts of human knowl-
edge, delivered at Columbia University during the academic year
1907-1908. 8vo, cloth. Price, $5.00 net.

LECTURES ON LITERATURE. A series of eighteen lectures on
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modern, delivered at Columbia University by Members of the
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