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Contemporary Issues

in Human Evolution

Editors

W. Eric Meikle

F. Clark Howell
Nina G. Jablonski

Wattis Symposium Series in Anthropology

CALIFORNIA ACADEMY OF SCIENCES

Memoir 21

San Francisco, California

Wattis Symposium Series in Anthropology

CALIFORNIA ACADEMY OF SCIENCES
Memoir 21

Mrs. Phyllis Wattis
May, 1996

Contemporary Issues
in Human Evolution

Editors

W. Eric Meikle
Institute of Human Origins, Berkeley, California
F. Clark Howell
University of California, Berkeley, California
Nina G. Jablonski

California Academy of Sciences, San Francisco, California

Wattis Symposium Series in Anthropology

CALIFORNIA ACADEMY OF SCIENCES
Memotr 21

San Francisco, California

December 2, 1996

SCIENTIFIC PUBLICATION COMMITTEE:

Alan E. Leviton, Editor

Katie Martin, Managing Editor
Thomas F. Daniel

Michael T. Ghiselin

Robert C. Drewes

Wojciech J. Pulawski

Adam Schiff

Gary C. Williams

or by any means, electronic or mechanical, including photocopying, recording, or any infor-
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ISBN 0-940228-45-9

Contemporary Issues
in Human Evolution

TABLE OF CONTENTS

Page

Portrait of Mrs. Phyllis Wattis .............. Frontispiece
Preface, Dy Nia GiJabionskt «2 2 4.4 se ed 6 oe wee BE: Vil
Thoughts on the Study and Interpretation of the

Human Fossil Record, by F. Clark Howell . 2... 0 0 l
Paleoanthropology and Preconception, by /an Tattersall .... . 47
Grades and Clades: A Paleontological Perspective

on Phylogenetic Issues, by Pascal Tassy 2... 4444.5 on 35
Homoplasy, Clades, and Hominid Phylogeny,

bywienry We Mcteniy. x eb hg oo ea eas rei
The Genus Paranthropus: What’s in a Name?,

Dy Kendig yi Clarke as 2 eae: Be ae Gh oe wn & oD 03
Origin and Evolution of the Genus Homo,

DY BEMGIAUVOGR! gan en we es a BES le ee es 105
Current Issues in Modern Human Origins,

by Christopher Bo siinger’ 4 ds w & hn oe Oe we 4 116
Behavior and Human Evolution, by Alison S. Brooks... . . 135
Molecular Anthropology in Retrospect and Prospect,

DY JOROTIAN MOTE 0.3 nce oe. o0%. aM we OS FSO w A 167

Vil

Preface

This volume represents the edited proceeding of the First Paul L. and Phyllis Wattis
Foundation Endowment Symposium, which was held at the California Academy of
Sciences on February 6, 1993. It represents the precious first child of two very
important parents. Its father was F. Clark Howell, world-renowned paleoanthropolo-
gist and Fellow of the California Academy of Sciences. It was Clark who, with the
help of dedicated assistants from the Anthropology Department at the Academy,
developed the theme of the Symposium and brought the key players together. His
efforts were only possible, however, with the blessing, inspiration and financial
support of the volume’s mother, Mrs. Phyllis Wattis. Phyllis Wattis’s passionate
devotion to the Academy, and especially to its anthropology programs, has been
matched by her extraordinary philanthropy. Her own keen interests in anthropology
and archaeology, combined with her commitment to public education, have resulted
in the development of an extensive series of educational programs at the Academy
that includes the Wattis Foundation Symposia.

The Wattis Symposia, born of Mrs. Wattis’s interests in anthropology and prehis-
tory, are aimed at bringing “state of the art” presentations on a seminal topic in
anthropology to the general public. The presentations are then echoed in published
form for distribution to an even wider public. The volumes of the Wattis Symposium
Series in Anthropology, the first of which you are now reading, take their place
alongside other numbered Memoirs of the Academy.

The first Wattis Symposium and its associated publication also owe their existence
to several other energetic and hard-working individuals. The former Irvine Chair of
Anthropology, Dr. Linda Cordell, in collaboration with Deborah Stratmann, also of
the Academy’s Anthropology Department, worked with Clark Howell to translate the
idea of the symposium into practice. Their dedication and success set the tone for the
entire series. This first volume was produced largely through the tireless efforts of
Dr. Alan Leviton, Director of Scientific Publications for the Academy, who crafted
the edited text into a handsome book.

As befits the nature of anthropology today, the Wattis Symposia are envisioned as
being explicitly multidisciplinary. The theme of the first symposium, human origins,
brought together widely recognized scholars from the fields of paleoanthropology,
vertebrate paleontology, archaeology and molecular anthropology. Future symposia
will do likewise for different subjects and will, to the greatest extent possible, integrate
scholarship from the four fields which constitute anthropology in its broadest sense,
namely, cultural anthropology, physical anthropology, archaeology and anthropo-
logical linguistics.

Vill

It is has been a pleasure to have been involved in the production of this first
symposium volume, which, we hope, will stand as a lasting tribute to the vision,
generosity and seemingly boundless enthusiasm of Phyllis Wattis.

Nina G. Jablonski

Irvine Chair of Anthropology
California Academy of Sciences
June 14, 1996

Thoughts on the Study and
Interpretation of the Human
Fossil Record

F. Clark Howell

Laboratory for Human Evolutionary Studies/Museum of Vertebrate Zoology
University of California
Berkeley, CA 94720

Human evolutionary studies are flourishing as evidenced here by a diverse set
of symposium contributions. This endeavor has acquired a subject matter for its
focus and an ever enhanced armamentarium of perspectives and methodologies
drawn largely from the natural and physical sciences. Thus, it is fundamentally an
aspect of evolutionary biology, most broadly conceived. As no one can master more
than a few such procedures and participate actively and intimately in more than
a limited spectrum of the overall endeavor, it has come to be greatly enhanced by
accretion of participant fellow scientists, of many callings. These have increasingly
been incorporated within the endeavor, rather than largely serving it from without,
and in so doing are accountable for its attendant transformation. As a consequence
it has manifestly gained in breadth as also in depth, and garnered a scientific
accountability, largely absent heretofore. Much of this development is often and
variously reflected in these contributions. In spite of the accelerated pace of
discovery and of manifold field, laboratory, and comparative researches, the
endeavor has been bedeviled by controversy. One may justifiably question the
extent to which normal science is practiced and a common paradigm, as a system
for examining the world, recognized and pursued. I discuss here briefly three areas
in which re-examination and redirection of perspective and procedure are sorely
warranted. Such are (a) the source, circumstances, and timing of the initial
hominin dispersal into Eurasia; (b) the treatment of hominin fossil representatives
as paleodeme (p-deme) samples, both independent of and preparatory to the
delineating and evaluation of clades (lineages); (c) some evidence relevant to
considerations of Homo sapiens origins and differentiation, the overall impact of
which is rejection and dismissal of hypothetical construals of so-called multire-
gional continuity models and their correlatives.

This volume is the outcome of a day-long symposium, held at the California
Academy of Sciences (Golden Gate Park, San Francisco) on February 6, 1993. Its
purpose was to expose to a lay audience basic theoretical, conceptual, and methodo-
logical issues about the way we approach and thus hope to understand the evolution
of humankind. The symposium was planned by the Academy’s Anthropology De-

Contemporary Issues in Human Evolution Memoir 21, Copynght © 1996
Editors, W.E. Meikle, F.C. Howell, & N.G. Jablonski Califomia Academy of Sciences

HOWELL

partment, in consultation with several external advisors. It was realized through the
generosity of the Paul L. and Phyllis Wattis Foundation, another example of its
continued concern for and support of the CAS over many years. For myself, and for
the other nine symposium participants, | wish here to record our great appreciation
to the Foundation, and particularly to Phyllis Wattis herself, for the opportunity
afforded us on this occasion. One participant was unable to provide a manuscript.
Prof. H. M. McHenry was subsequently asked to fill this gap in the proceedings; he
generously agreed to do so, and to him the editors offer their warmest appreciation.

I played a small part in the initial planning for the symposium, for two reasons.
Firstly, | greatly appreciate and value this Academy and the role it plays both in
fundamental research and in broad dissemination of science knowledge. It is a most
important institution within the state of California, and particularly so in the Bay
Area. And, secondly, because human evolutionary studies center on a search to
elucidate our own history, in all its aspects, within the broader context of the
emergence, diversification, and (frequently) extinction of life forms on this planet.
Thus, it is deservedly every man’s study and concern, rather than the preoccupation
of a privileged few devotees. Occasions such as this do afford specialists the useful
opportunity not only to interact with one another, as often transpires at scientific
assemblies, but especially to share with a broader, non-specialist audience their
particular concerns and involvement in scientific problems of broad, general interest.
This ts only as it should be, and certainly human evolutionary studies deservedly have
a very substantial following.

There are many facets to human evolutionary studies, only some of which are
exemplified in these symposium contributions. These include the higher primate
perspective from primatology, the fossil and archeological records and their contexts
from paleoanthropology, and the nature and extent of modern human structure and
individual and population variability from human biology and molecular biology.
The last is among the less well represented here (except, in part, in the contribution
by Jon Marks). In each of these major foci there have been major developments, rapid
advancements, and shifting perspectives as a consequence of accelerating research
programmes, development and application of new methods and analytical proce-
dures, and new or different frameworks afforded by altered theoretical perspectives
from various affiliated disciplines. Thus, it is oft times difficult to affirm a consensus
view in the light of such substantive enhancement of data bases and rapid shifts in
approaches to, and analysis of, such expanded resources. Nonetheless, the major
outlines and scope of an evolutionary science of paleoanthropology has emerged
within the past two decades. Such an endeavor had its roots back at least to the turn
of the century, and a long and sometimes painful gestation in the course of the
subsequent fifty years. The impact of the maturation and crystallization of modern
evolutionary biology, exemplified in the well-known modern synthetic perspective,
was somewhat delayed in human evolutionary studies relative to other endeavors in
paleobiology. Population genetics, whose application to human populations was
initiated some fifty years ago (blood groups), became an integral part of human
population biology only some four decades ago (with subsequent expansion of studies

HUMAN FOSSIL RECORD 3

of serum proteins and HLA). The explosive effects of molecular biology, as initially
applied to primate relationships (protein sequences) are some thirty years old, and as
applied more directly to human evolution (analysis of DNA variation) are mostly less
than half as old. However, the latter has strong evolutionary and phylogenetic
components such that it has tended to enhance and strengthen bridges between human
evolutionary biology and human paleobiology (as paleoanthropology). It may well
be that some preliminary results of molecular biological investigations of human
populations have been initially enthusiastically over-interpreted; nonetheless, it can
scarcely be denied that the impact of such researches has been very substantial and
that ultimately the phylogenetic and biogeographic significance of such investiga-
tions will prove to be indeed far-reaching.

There is no encompassing theory of hominid evolution. (That 1s, if by theory is
meant an argument invoked or constructed to explain why the world ts as it appears
to be.) Alas, there never really has been despite claims to the contrary drawn from
the recitation and some critical analysis of so-called classic texts. For the most part,
as evidenced for example in Bowler’s (1986) Theories of Human Evolution, such are
largely speculative excursions and, frequently, comprise inferences in respect to
humanity’s place in nature, and varied inexplicated accounts of sequence(s) of events
inevitably leading to modern humanity. These scenarios or narrative treatments, as
Landau (1991) has shown (in Narratives of Human Evolution), may often have a
common focus on a set of components, entailing transformational events in respect
to habitats, lifeways, dietary adaptations, or behavioral potentialities (often in relation
to central nervous system structure). These have been recognized as variously ‘fossil
—free’ and, one should add, ‘context-poor’. There is a dearth of development of
axioms, of theory construction, of hypothesis formulation and testing, etc., in respect
to scientific methodology and scientific explanation. Moreover, as Salmon (1990:32)
remarks, “the mere recital of just any set of preceding occurrences may have no
explanatory value whatever, the narrative must involve events that are causally
relevant to the explanandum if it is to serve as an explanation.” Such a relationship
is too frequently a subject of assertion rather than demonstration.

The record of the hominid past 1s an unobservable to be discovered, recognized,
and appropriately investigated in its own right. Although there have been significant,
indeed remarkable, advances in documentation of the fossil and attendant archeologi-
cal records, there clearly remains scant 1f any representation, and hence knowledge,
of some potentially important and certainly relevant spatio-temporal realms. This is
particularly reflected in deficits in documentation of (a) the earliest Pliocene of Africa
(only recently has the recovery of Ardipithecus ramidus opened this vista); (b) the
initial (immigrant) hominid inhabitants of Eurasia; and (c) some substantive gaps in
the Pleistocene record in some major areas and particular time spans in Eurasia as
well as Africa. As a consequence of fundamental primary data deficiencies, investi-
gators are limited in respect to the kinds of issues that may be addressed, in the ability
to effect comparisons, and of course in respect to the recognition of issues as yet
wholly inevident (‘unobservables’).

Although the import of newly discovered documentation is often down-played,

4 HOWELL

even dismissed, the ultimate impact of such acquisitions are in fact overall momen-
tous, and not infrequently profound. They are often surprises and may well eventuate
in that essential tension’ that leads to entirely new and unforeseen perspectives. The
lag between such instances and their consequent impact is often substantial, as has
been documented repeatedly in the growth of paleoanthropology. It is also worth-
while to stress that, in part as a consequence, subject matter and problems undergo
examination and investigation from different perspectives, varying methodologies,
and unlike disciplinary frameworks such that the results are attended, oftentimes, by
varying degrees of acceptance, skepticism, outright rejection, and associated contro-
versy.

Many disciplines bear upon and potentially contribute ultimately to paleoanthro-
pological endeavors. Each has its specialists and practitioners, and there has been an
ever-accelerating trend toward multi- and cross-disciplinary research undertakings,
particularly in field-focused efforts of exploration, data recovery, and consequent
laboratory analysis. Despite such important and necessary progress, there frequently
remains a notable lack of cross-disciplinary comparison, analysis, and integration
requisite to the maximization of such particular research endeavors in regard to their
bearing on fundamental issues in human evolutionary studies. Among others this is
particularly manifest in respect to advances in chronometric dating, paleoenviron-
mental studies, paleogeographic reconstructions, taphonomice studies, analytical and
distributional aspects of lithic assemblage studies, in the application of methods of
cladistic analysis, and in the intensification of ontogenetic and biomechanical/fune-
tional studies relevant to the hominid fossil record. These disparities, coupled with
differing reliances on and commitments to strongly contrastive methodologies and
explicit (or implicit) frameworks of scientific explanation and hypothesis-formula-
tion and testing are in no small part responsible for some major controversies and for
attendant adversarial and polarized positions in respect to certain familiar problem
areas across much of paleoanthropology.

Actually, developments in all aforementioned subject areas have experienced such
significant advances as to impact importantly on the scope and nature of paleoanthro-
pology. This is sufficient to transform it from the current emergent state into a
full-blown, individuated discipline, having its own parameters, goals, procedures,
methodologies, problem areas, and central issues. Paleoanthropology is close to a
paradigm state without yet having achieved it. Unfortunately, that condition is
insufficiently defined due in part to some significant consensual faults, and in part to
the lack of adequate, explicit integration as a consequence of still often fragmented,
unfocused aspects of some very relevant endeavors.

A few remarks are offered here in respect to some subjects of chapters in this
volume. In each instance there is an important historical background, sometimes an
extensive one, and the current states of researches in such instances reflect not only
increments in data acquisition but also the impact of newer methodologies which
together have led to enhanced understanding and, sometimes, substantially altered
perspectives.

It has long been considered that the extant great (anthropomorphous) ape genera

HUMAN FOSSIL RECORD 5

are more or less closely related and together form a higher taxon, either at the familial
(Pongidae) or subfamilial (Ponginae) level. Similarly, the close affinity of the two
African apes (Pan, Gorilla) vis-a-vis the distinctive orangutan (Pongo) has been
widely accepted for well over a century (see Schultz 1936). This last conclusion has
been extensively supported in the past thirty years by numerous biomolecular
investigations, of several systems, that not only affirm this view but also reveal the
rather unexpected close resemblance (affinity) of the African taxa to the human
species (traditionally Hominidae) rather than the more distant Asian taxon. Conse-
quently, the aforesaid familial/subfamilial rank must be disassembled, and the
African ape-human lineages must be conjoined in a taxon of higher rank (Andrews
1992). Thus, and according to requirements of priority rules, family Hominidae
includes extinct and extant apes and humans; African apes (Gorillini) and humans
(Hominini) are joined in the subfamily Homininae; orangutans (Pongin1) and extinct
relatives (Sivapithecini) are joined in the subfamily Ponginae; other extinct ape
groups also constitute tribes (3, at least) in another subfamily (Dryopithecinae).
Substantial and repeated claims from some dozen molecular studies, thoughtfully
discussed and evaluated recently by Bailey (1993), have been made for an immediate
close affinity of chimpanzee (Pan) and human (Homo sapiens), relative to gorilla,
which if validated would place both within Hominini. Others, including Marks in this
volume, have been equally adamant in their insistence that the available evidence is
still inconclusive and that the branching arrangement among these three taxa consti-
tutes a still unresolved trichotomy. This happens to represent my own persistent view
of such evidence, which is reinforced by a wealth of ontogenetic observations
(Hartwig-Scherer 1993) reflecting the distinctive growth pattern of Homo relative to
that shared by Pan and Gorilla. However, increasingly the closeness of Pan and
Homo is being convincingly forced upon us as a consequence of intensified bio-
molecular studies. The extant African ape trio remains the essential outgroup for
comparisons, cladistic or otherwise, for Hominini, However, the view that ‘the
chimp’ is ‘the model’ for ancestral Hominini is still inferential and, until now, lacks
adequate support from the hominid fossil record (which is almost non-existent
between 8 and 4.5 Ma).

The denomination of Australopithecus africanus by Raymond Dart in 1925 was
both unwelcome and severely criticized by a concerned majority of the scientific
establishment. Broad, but non-unanimous, acceptance of such an extinct “man-ape’
or ‘ape-man’ into Hominidae (= Hominin1) required over a quarter century to achieve.
How can a situation such as this, constituting such a paradigm-enhancing contribu-
tion, be explained? In spite of some critical analysis of this event, it has still to receive
in-depth study, and any explanation can only be attributed broadly to the (unspecified)
realm of the existential. Nonetheless it can be argued that the validity of the genus
was demonstrated within five or so years, and that its polyspecific nature was
demonstrated by a decade later. Two further decades were required both to validate
the proposal of multispecific taxa and simultaneously to reveal the sagacity of Robert
Broom in his proposal (in 1938) of a separate higher taxon (Paranthropus) to
accommodate the unparalleled range of variation in the then known hypodigm. In

6 HOWELL

fact it would require another quarter century before the Australopithecus/ Paran-
thropus dichotomy would receive the concerted and serious consideration it merited
for so long. Clarke offers here a welcome overview, from historical, morphological,
and adaptational perspectives, of the australopithecine radiation, for indeed it was
such, from his own deep familiarity with the primary fossil collections. It is now both
misleading and inappropriate to consider, as was once commonly done, such homi-
nid(s) as the root or link in the hominin lineage. There are minimally three well-de-
fined lesser taxa (species) of Australopithecus, and upwards of five such of
Paranthropus. In each instance lesser taxa have disjunctive distributions between the
eastern and southern African subregions. Several distinctive taxa considered refer-
able to Homo are now well documented as having co-occurred, evidently sympatri-
cally, with Paranthropus species in both subregions.

For many decades evidence of very early representative(s) of Homo remained
wholly unknown. In fact, claims for great, even Pliocene, antiquity of this genus have
been repeatedly advanced and as often vigorously rejected by some then — influential
members of the scientific establishment for upwards of a century. A growing
understanding of late Cenozoic biostratigraphy and of the earlier Paleolithic some
forty years ago indicated the absence of hominin documentation in Eurasia until well
into the mid-Pleistocene; the record in Africa was dominated by australopithecines
(in the south) and a few purportedly H. erectius-like fossils (in the Maghreb). The
subsequent two decades witnessed the intensification of researches in the Olduvai
basin and, subsequently, the initiation of protracted, large scale field efforts in the
greater Turkana Basin. This led to the recovery, recognition, and denomination of
Homo habilis in an isotopically dated context at Olduvai and its further confirmation
in the Turkana basin, along with increasing numbers of at least one other taxon clearly
representative of another, further derived representative of Homo. Together these
discoveries have afforded a wealth of hominin documentation in the 2.0-1.4 Ma time
span, forced re-examination of emerging conceptions of variability, taxonomy, and
potential phylogenetic affinities of these newly acquired fossil samples, and initiated
ever-expanding research programmes focused on the most ancient Paleolithic occur-
rences documented anywhere in the world. Wood discusses here this fossil record
and evidence it affords for a multiplicity of ancient African Homo taxa (H1. rudolfen-
sis, H. habilis, and H. ergaster), for attendant extinctions, and implications for greatly
enhanced insight into the roots of subsequent hominin evolutionary developments.

Anextra-African dispersal of hominins into Eurasia became an important tenet of
paleoanthropology within recent decades due to a much enhanced African fossil
record of the better delineated Pliocene interval. The most approximate time for this
extensive range expansion appears now to have been broadly coincident with or just
after the Olduvai (N) subchron (sc), ~1.96-1.78 Ma. Two occurrences in western
Asia, Erq el Ahmar (southern Jordan valley) and Dmanisi (Georgian Caucasus)
seemingly constitute the nearly first manifestations of the dispersal event, which is
very well-documented subsequently at "Ubeidiya (central Jordan valley) at ~1.4 Ma.
Recent isotopic (Ar/Ar) age assessments (Swisher e7 a/. 1994) of fossiliferous (and
hominin) occurrences in Java, at Perning (~1.8 Ma) and at Sangiran (~1.66 Ma),

HUMAN FOSSIL RECORD 7

coupled with redefined paleomagnetic evaluations, indicate an unexpectedly en-
hanced antiquity for hominin penetration into Sundaland, apparently toward the close
of the Olduvai sc, and certainly not long thereafter. In fact there is now purported
temporal overlap between those occurrences and the temporal range (in eastern
Africa) of both H. ergaster and H. habilis. The Perning hominin occurrence lacks
taxonomic substantiation, whereas at Sangiran, in spite of some strong opinions to
the contrary (Kramer 1993, 1994; Kramer & Koenigsberg 1994), multiple hominin
taxa appear very likely to be represented early on. Clearly such a dispersal ‘event’
requires reconsideration and more explicit formulation, and full description and
in-depth comparative analyses of appropriate Javan hominin specimens from the
oldest reaches of that fossil record are sorely needed. Similarly, the seemingly belated
appearance of hominins in continental eastern Asia, perhaps some 1.0-1.2 Ma, now
requires fuller analysis and explication. Hominin occupation of this or still greater
antiquity has been claimed at times, and even now, for Europe. However, incontro-
vertible evidence to support such a perspective has not been readily forthcoming in
spite of the expenditure of much effort in the search. Personally, I consider that some
claims for such antiquity are overstated and as yet unconfirmed. However, others
may well be valid, both in southwestern and in central/eastern Europe, and | remain
more sanguine than some others (Roebroeks 1994; Roebroeks & van Kolfschoten
1994) about the potentiality, even probability, of hominin presence in the southern
reaches of Europe in the late Matuyama chron, broadly 1.5-1.0 Ma. This view is now
supported by the newly documented, and incontrovertible conjoint faunal/artifactual
occurrence in the Baza sub-basin of the Guadix-Baza intramontane (Betic system)
basinal complex of Andalusian Spain, almost comparable in antiquity to that of
*Ubeidiya in the Levant. Nevertheless, much fuller documentation ts still required
for verification of some claims, and ultimately only new occurrences, in incontro-
vertible and dateable contexts, will enable resolution of this issue. It remains true,
certainly, that the most substantive and informative body of evidence falls within the
Brunhes (N) chron (i.e., < 0.78 Ma).

Neontologists tend to view evolution from the top down (present to past) and
paleontologists from the bottom upwards (past to present). In each instance the
present (and fully ‘known’) is given and the past is largely ‘unknown’. Neontologists,
because of their focus on ‘known’ and knowable, have quite different expectations
with respect to the unknown (and unknowable) past than the paleontologist, im-
mensely reliant upon and grateful for whatever is at hand at his/her particular moment
in time. The former can never be sufficiently satisfied by the evidence afforded by
the past, whereas the latter is continually reassured as such evidence as there might
have been comes to be enhanced. Although sharing a common goal, focused on
comprehension of evolutionary pattern and processes, their perspectives and ap-
proaches are recognizably unalike and their consequences are correspondingly dif-
ferent. Such distinctions are relevant in regard to human evolutionary studies, and in
particular to treatment of the documentation afforded by the hominin fossil record.
There is an accumulated historical baggage of phylogenetic inference and attendant
scenarial speculation that can only be considered now as of little value and scant

8 HOWELL

meaningfulness, in the same way as we might consider pre-Newtonian mechanics
and pre-Keplerian planetary astronomy. T. H. Huxley long ago remarked that “the
greatest tragedy in science is a beautiful hypothesis murdered by an ugly fact.” And
John Dewey put the matter this way:

Old ideas give way slowly, for they are more than abstract forms and categories.

They are habits, predispositions, deeply engrained attitudes of aversion and preference.

Moreover, the conviction persists — though history shows it be a hallucination — that all

the questions that the human mind has asked are questions that can be answered in terms

of the alternatives that the questions themselves present. But, in fact intellectual progress

usually occurs through sheer abandonment of questions together with both of the

alternatives they assume — an abandonment that results from their decreasing vitality
and a change of urgent interest. We do not solve them: we get over them. Old questions
are solved by disappearing, evaporating, while new questions corresponding to the

changed attitude of endeavor and preference take their place. (Dewey 1910:19)

One might thus be reminded of Planck’s depressing dictum that a “new scientific
truth does not triumph by convincing its opponents and making them see the light,
but rather because its opponents die, and a new generation grows up that is familiar
with it” (Planck 1950; see Hull 1989:ch. 3). In fact such is not necessarily or
frequently the case, as any even cursory examination of much history of science
reveals other factors, perspectives, and empirical resources frequently play a decisive
role.

In recent years investigators have confronted anew the issue of species and clades
in the hominin fossil record. The difficulty of employing the otherwise broadly
accepted and widely employed biological species concept in paleobiology is com-
monly acknowledged. Some version of a phylogenetic (evolutionary) species concept
is frequently proposed toward resolution of this issue. Such might include E. O.
Wiley’s (1978:18; 1981:25) reformulation of G. G. Simpson’s evolutionary species
concept as “a lineage of ancestral— descendant populations which maintains its
identity from other such lineages and which has its own evolutionary tendencies and
historical fate” (essentially a biological species concept, invoking reproductive
continuity/individuality through time). The lineage is construed as “one or a series
of demes that share a common history of descent not shared by other demes.” The
phylogenetic species concept (of Eldredge & Cracraft 1980:92; Cracraft 1983:170;
Cracraft 1989:35) is considered “an irreducible (basal) cluster of organisms diagnos-
tically distinct from other such clusters, and within which there 1s a parental pattern
of ancestry and descent.” Operationally, this implies diagnostic, heritable character(s)
and reproductive cohesion within clusters (demes or related, larger aggregates).

The critical component in most such delineations is the deme, considered “‘as the
unit of natural history and of evolutionary divergence,” and defined as “a communal
interbreeding population within a species” (Carter 1951:142), or, following Mayr &
Ashlock (1991:413), “a local population of a species; the community of potentially
interbreeding individuals at a given locality.” The term was introduced by Gilmour
& Gregor (1939) fora local interbreeding population or community (“any assemblage
of taxonomically closely related individuals”), and distinguishable by reproductive
(genetic), geographic, and ecological (habitat) parameters. Together, demes (some-
times as isolates) constitute subspecies, the “aggregate of local populations of a

HUMAN FOSSIL RECORD 9

species inhabiting a geographic subdivision of the range of the species. . .” (Mayr &
Ashlock 1991). It is well known that much of the hominin fossil record is charac-
terized by fragmentary and otherwise incomplete skeletal parts such that even an
individual, drawn of course from a deme, may be quite imperfectly known. Important
(and notable) exceptions are those singular collections of multiple and more exten-
sively preserved individuals — as instanced among Australopithecus species (Hadar
locality A.L. 333, Sterkfontein-Mb. 4), Paranthropus species (Swartkrans-Mb. 1),
Homo erectus (ZKD-1, Ngandong), Neandertals (Krapina) and antecedents (Sima de
los Huesos, Atapuerca), and Homo sapiens palestinus (Skhul, Qafzeh) — that afford
significant demic samples. Such are of course spatio-temporally disparate, regionally
localized samples of paleodemes (p-demes). Due to the disjunctive distribution of
late Cenozoic continental sediments, in whatever geological setting, it is rare indeed
to have much spatial (geographic) documentation of subspecies distribution and
variation from a suitable series of p-demic samples.

P-demic samples are the basic stuff of the hominin fossil record. Trinkaus (1990)
has also considered that “the best approach . . . is probably one that regards the
available fossil samples (or specimens) as representatives of prehistoric populations
or lineages acting as portions of dynamic evolutionary units.” A central problem has
been, and remains, that of bridging the gap between individual specimens and such
p-demic samples to achieve an appreciation of the subspecies and its variation. Finds
from the earlier history of human paleontology, including types and/or less complete,
fragmentary specimens always require re-evaluation in the light of fuller information
afforded by both more complete and numerous remains recovered subsequently. This
obvious choice is not always sufficiently appreciated or adequately pursued (however
common practice in paleontology). After an early history and long persistence of
species recognition and taxonomic splitting (Campbell 1965), human paleontology
has often been dominated by an overriding concern with subspecies and attendant
reluctance to confront the issue of species lineages. Thus, there is the further problem
of the delineation of species lineages on the basis of evidence afforded by p-demic
samples, however substantial or (more often) limited. This is a problem faced by
paleontologists for generations, but one too often evaded by students of the hominin
fossil record.

lan Tattersall (as summarized in this volume) has been most vocal in his opposition
to such practice. He has observed, rightly in my view, that “In any group other than
Hominidae the presence of several clearly recognizable morphs in the record of the
middle to upper Pleistocene would suggest (indeed, demonstrate) the involvement of
several species” (Tattersall 1986:170). Thus, to him, “The interpretation of most
human fossils subsequent to about 0.5 myr as belonging somehow to Homo sapiens
is perhaps the most comprehensive smoke screen of all, and could only have been
maintained by a zealous refusal to consider characters other than brain size” (Tatter-
sall 1986:169). And, he further concludes “that there is neither theoretical nor
practical justification for continuing to cram virtually all fossil humans of the last
half-million years into the species Homo sapiens” (Tattersall 1992:348). I would add
that the whole of the history of genus Homo is increasingly being viewed by some

10 HOWELL

(thankfully few) students of human evolution as remarkably free of the usual events
— adaptive radiation, diversification (including cladogenesis), divergence, stasis,
endemism, extinction, dispersal and range extension, etc. — upon which paleobiolo-
gists commonly focus their attention. Certainly to many of us, this suggests that some
perspectives and certain hypotheses concerning the evolution of genus Homo are far
wide of the mark. There is scant reason to marvel over the lack of concurrence among
investigators so long as such profound and fundamental divergences continue to be
manifest.

Some frameworks of hominin evolution strongly smack, if not of orthogeneticism,
at least of outright progressivism. Gould (1988:319) considered evolutionary pro-
gress “a noxious, culturally embedded, unstable, non-operational, intractable idea
that must be replaced if we wish to understand the patterns of history.” If not overtly,
at least covertly the usage of stage and grade concepts persist, the latter leading surely
at times to paraphyletic groupings. Familiar ascriptive terms in human paleontology,
aside from ‘primitive,’ include ‘archaic’ (adj., characteristic of a much earlier, often
primitive period); ‘intermediate’ (adj., lying or occurring between two extremes, in
a middle position; a gradistic term, frequently employed as a noun and conflated with
intergradation); ‘transitional’ (adj., passage from one form, state [stage] to another,
and similarly gradistic); and, faux de mieux, ‘anatomically-modern’ (as the redundant
compound noun, ‘anatomically-modern human’). All such terms would seem to have
no effective role in the vocabulary of (human) evolutionary biology. Where is the
study of historical, evolutionary events? Of branching sequences? Of ancestral
morphotypes and their derivatives? Of structural complexes, their functional analysis,
and their transformations? Of genetic isolates and p-demes? Is there no role for
endemism? Indeed, are current studies of human evolutionary biology informing us
realistically of the pattern of hominin phylogeny? Alas, the only response is too often
in the negative.

Set out in the remainder of this chapter are several issues that particularly merit
re-examination from new or at least different perspectives if elucidation of hominin
phylogeny is a central goal of human evolutionary studies.

Primary Dispersal(s) of Homo Species

The nature of initial, ancient Eurasian hominins and their presumed A frican source
are critical components in elucidating the subsequent phylogeny of genus Homo. The
African source is now generally acknowledged to have been H. ergaster (= H. aff.
erectus of some authors), the known age range of which, in East African rift localities,
is 1.85-1.5 Ma. The oldest known extra-African hominin occurrence is in western
Asia, at Dmanisi (Georgian Caucasus), in a purportedly comparably ancient situation
(Olduvai [N] sc) (Gabunia & Vekua 1995). While admittedly sharing some (presum-
ably) primitive features with African (Turkana Basin) analogues, Dmanisi is demon-
strably derived, both gnathically and dentally, and is thus unique.

A hominin locality in eastern Java, that of Perning, is now considered of broadly
similar antiquity (1.81 Ma), and another central Javan locality (at Sangiran dome),

HUMAN FOSSIL RECORD ll

with an age of 1.66 Ma, falls similarly within the temporal span of the African species
(Swisher et al. 1994). The distance between the African and Indonesian Sunda Shelf
occurrences is 76° of longitude. At Sangiran some hominin cranial and gnathic
remains not originally attributed to H. erectus erectus, demonstrably provenienced
to the Grenzbank (conglomerate) and underlying Pucangan clays, apparently diverge
markedly and fundamentally from penecontemporaneous A frican H. ergaster. How-
ever, some material from the same geological horizon(s) is commonly attributed to
H. erectus. If, as seems most probable, multiple hominin taxa are represented in the
eastern (Sundaland) extent of this range, at ~1.6 Ma, is it appropriate to view H.
ergaster as the single source of such taxa and, as well, of all subsequent hominins?
To what extent should effects of insularity and faunal filters be considered in respect
to the initial peopling by hominins of the Sunda Shelf, as well to their subsequent
evolutionary history?

There is no such documentation in the whole of Europe, and still scant documen-
tation even of hominin presence there prior to ~1.0 Ma. Were perhaps subsequent
African populations the source of European hominins, particularly as (Asian) H.
erectus has, as yet, not been documented to occur in Europe? Some phenetic
resemblances have at times been noted between some hominin samples from the
earlier mid-Pleistocene time range of southern Europe and others from sub-Saharan
Africa. Are such purported resemblances real, and to what extent is this indicative of
genetic affinities as opposed to homoplasy?

Students of hominin evolution have been chary of the consideration of population
dispersals, range extensions, constrictions, ebbs and flows, etc. Tchernoy (1992) has
recently discussed, albeit only briefly, aspects of dispersal and varied terminological
usages in evolutionary ecology and biogeography. It would seem that paleoanthro-
pologists have envisioned a sort of one-time, one-way out of Africa scenario that set
the stage for all subsequent (and attendant) hominin evolutionary events, with the
dispersal, perhaps really a sort of persistent, accelerating range extension, presump-
tively expanding so as to fill all appropriate habitats, overcoming or by-passing
formidable barriers, rather like filling an empty saucer. However, might not the
process have been more akin to filling a muffin pan or egg carton, being comprised
of more limited and restricted or compartmentalized intrusions leading to patchy,
even sporadic and impersistent, distributions, differentiated by barriers in space and
through time?

Demes — Continuities, Discontinuities,
and Pleistocene Hominin Clades

Within species patterns of variation reflect the summation of subspecific variabili-
ties as measured across demic samples. The biological species concept is not
immediately applicable to fossil samples; demic and subspecific entities are of course
represented in the fossil record, as in extant species. Thus, as Shea er a/. (1993:281)
have strictured, “The most rigorous course open to the paleobiologist is to indirectly
test patterns and distributions within the fossil sample against those derived from

12 HOWELL

careful analysis of both species and subspecies of close phylogenetic relatives and
groups occupying similar ecological and adaptive zones” [italics in original].

As Harrison (1993:362) points out, it is “important to identify species groupings
as an initial step in a cladistic analysis, and not to use cladistics as a method to identify
species groupings.” Thus, because “species can only be identified in the fossil record
in terms of morphological criteria, and although there are no absolute rules for the
recognition of species boundaries, intuitive ideas of the range of well-known extant
groups provide models for the inclusion or exclusion of individuals.” Hence, “fossil
species are recognized by employing entirely phenetic concepts based on analogs
derived subjectively from morphological ranges of variation seen in modern species.”
Nonetheless, and as frequently acknowledged, strict reliance on degree of (phenetic)
resemblance may be hazardous and even misleading. Simpson (1963) thus noted that,
“As a rule with important exceptions, degrees of resemblance tend to be correlated
with degree of evolutionary affinity. Resemblance provides important, but nor the
only, evidence of affinity” [italics in original].

Multivariate studies of craniometric variation in extant large-bodied anthropomor-
phous apes “discriminate in statistically significant fashion among the three primary
groups (or multiple local populations) of P. troglodytes” (Shea et al. 1993), with
Mahalanobis D? values ranging between 1.416-2.166 (or 1.79-3.81 ina prior analy-
sis), whereas in G. gorilla D? values between demes of three different subspecies are
2.01-4.46 (mean, 3.51) and between demes of the same subspecies are 1.37-2.29
(mean, 1.76) (Albrecht & Miller 1993). Howells’ (1989; also 1973) extensive
multivariate analyses of craniometrics in 28 modern human samples afford invaluable
in-depth documentation of within-group and between-group variability and enable
various levels of cluster analysis and distance assessment between samples, geo-
graphic areas, and additionally, numbers of late prehistoric and subrecent samples.
Howells’ work demonstrates that recent humans are “cranially rather homogeneous,
with a limited dispersion of character” (1989:16); he states, “the impression, true or
not, is that the modern unity is fairly recent” (1989:70). Examples of regional
(including intracontinental) D? values are those among three African samples, 4.3-
5.4, and between such and Bushmen, 5.7-6.8; among three Australasian samples,
4.1-5.1, and between such and Andamanese, 6.6-7.5; and among four East Asiatic
samples, 2.9-4.0 (2.6 between two Japanese samples), and between such and Ainu,
4.9-5.4. Minimum D* distances recorded were within Europe, 2.9; maximum distance
recorded was 9.9 (between north Asian, Buriat, and Australian aborigines). The latter
is similarly reflected in the dentition differences recognized between Sinodont/Sun-
dadont and Australasian population aggregates.

Simpson (1963; also 1961) made important distinctions in respect to the language
employed in taxonomy and different designative words (names, terms) and their
kinds, with particular regard to processes, name sets, and referents (see Figure 1). He
especially noted, in reference to hominin evolutionary studies, that “one of the
greatest linguistic needs in this field is for clear, uniform, and distinct sets of N; and
N> designations, applied to specimens and to local populations as distinct from taxa.”
It is well known that innumerable workers concerned with hominin paleontology

HUMAN FOSSIL RECORD 13

Nu: designations N»: designations Ny nomina Na: hierarchic No: designations
of specimens of populations, terms of classifications

statistical taxonomic hierarchic collocation, superordination
SAMPLE *-—_——————~ POPULATION TAXON... CATEGORY, -——______ GL ASSIFICATION

(includes hypodigms inference inference assignment and subordination

of taxa and types of

nomina)

FIGURE 1. “Schema of processes (arrows), name sets (N), and references (capitals) in
taxonomy. Vertical arrows all represent the processes of designation or symbolization. The
processes represented by horizontal arrows proceed logically from left to right, but in practice
no one operation can be carried out without reference to the others. These arrows are therefore
drawn pointing both ways.” (Simpson, 1963.) (Permission to reproduce courtesy of the
Wenner-Gren Foundation for Anthropological Research.)

have been notoriously imprecise in their usages, often skipping confusingly between
what are in fact distinct entities and concepts. The specification of different name
sets (N) is requisite and mandatory for any measure of consistency and progress in
this endeavor. Following Simpson the essential distinctions are: N, = specimen
(object) designation (locality name, repository/catalogue numbers; = hypodigm-1);
N> = group designations, population (paleocommunity or p-deme in author’s sense)
designation, reflecting inclusive (genealogically) related geographic group(s) (=
hypodigm-2); N; = formal nomen or taxon, composed of N> hypodigms as drawn
from and representative of subspecific and specific taxa (= hypodigm-3); Ny =
ranking designation, categorization within a hierarchic (Linnaean) classification. It
should be stressed of course that the single (N;) type, referring to a chosen holotype
or, failing that, a subsequently designated lectotype, functions as a name bearer (or
onomatophore, in Simpson’s one-time usage) for a particular biological entity. It is
not, and cannot function as, reflective of a full or inclusive spectrum of character
states or their variations, and so on. However, N> designations are indeed revelatory
in those respects. I consider that the N> designation is greatly undervalued and
under-employed, yet as Simpson states “it is often necessary to recognize and
designate a local population that is a part of a taxon but does not in itself comprise a
whole taxon,” and, thus, “for some populations a different set of names or symbols,
N>, may therefore be required.” In the fossil record such p-demes exhibit bounded-
ness, spatio-temporally.

Upwards of twenty such p-demes are distinguishable within the immediate ances-
try subsumed within Homo, exclusive of the H. habilis and H. rudolfensis taxa, and
exclusive of, in the strict sense, Homo sapiens (= ‘anatomically-modern’ humans of
authors). It is to such p-demes, or some members thereof, that much comparative and
analytical study has been devoted, although the demic focus has not always, even
often, been made sufficiently explicit.

14 HOWELL

The Principal Distinguishable African Hominin P-demes Are:

Nariokotome. Fortunately there are three partial skeletons within this group: a
subadult skeleton (WT-15000); another attributed (pathological) partial skeleton
(ER-1808); and the first discovered example, comprising associated cranial parts,
mandible, and some postcrania (ER-730). Crania (ER-3733, -3883) and adult (ER-
992, the type of the nomen, ergaster Groves & Mazak) and subadult (ER-820)
mandibles are well-represented, and there are as well a number of referred and varied
postcrania. A representative of this group is also documented at Konso-Gardula
(southern Ethiopia). This deme is probably also represented (partial cranium SK. 847,
etc.) at Swartkrans (Mb. | units). Paranthropus boisei (in eastern Africa) and P.
crassidens (in southern Africa) are sympatric australopithecine taxa at all known
localities/temporal intervals.

Olduvai/LLK-II. The calvaria of Olduvai Hominid 9, of rather uncertain strati-
graphic provenance, is the principal specimen. It is the type of the nomen, /eakeyi
Heberer. A smaller, partial cranium (VEK-IVa-12) exhibits comparable morphology.
Direct associations of mandibles and crania are still unknown, but two partial
specimens (hemi-mandible O.H.-22, and fragment O.H.-51) are possible candidates
for this p-deme. The only likely postcrania (innominate, femoral diaphysis) may be
those of WK-IV(a), O.H.-28.

Tighenif (Ternifine). This p-deme is, for now, recognizable only in the northwest
African Maghreb. The cranium is unknown except for a parietal, whereas three
mandibles with dentition are well represented, as are some nine isolated teeth, all
from the eponymous locality. A mandible (T-1) is the type of the nomen, mauritani-
cus Arambourg. In known elements there are both (derived) distinctions from, and
some resemblances to, the Olduvai/LLK p-deme hypodigm — but comparisons are
weakened by either insecure attributions (at Olduvai) and/or poor cranial repre-
sentation (Tighenif). A single postcranial (femoral diaphysis) might be considered,
parsimoniously, as representative of this p-deme (from Ain Maarouf = El Hajeb).
Probably attributable to a similar, and thus presumably related, p-deme are geologi-
cally younger gnathic-dental remains from Sidi Abderrahman (Littorina Cave-F;
Thomas Quarry-1) and calvarial (frontal) and dental remains (Thomas Quarry-3). The
Salé partial cranium unfortunately affords a most incomplete and imperfect charac-
terization of calvarial morphology due to its quite extensive (occipital) pathology; its
demic affinities are obscure.

Kabwe. The type of the nomen rhodesiensis Woodward is represented by a
complete adult cranium (Kabwe — NNM. E-686). It is still the most complete indi-
vidual cranium of this p-deme. Other individuals are represented by partial maxilla
(K-2, E687) and parietal (K-3, E897); some three individuals are represented by a lot
of fragmented parts of the axial (sacrum, innominate) and upper (humerus) and lower
(femora, tibia) appendicular skeleton, of uncertain association and provenance. An
additional calvaria from Elandsfontein corroborates closely the morphology of the
first found individual. Additional representatives probably include the Ndutu cra-
nium, and only conceivably Olduvai Hominid 23 (Masek beds), a mandible fragment.

HUMAN FOSSIL RECORD 15

Tentatively attributed to this group is the Bodo (Middle Awash) cranial specimen,
which shares most derived features with Kabwe and but few with the Olduvai/LLK-II
individual. The extremely fragmentary condition of Eyasi-! leaves uncertain its
potential affinities in respect to this group. Hominin remains from Melka-Kontoure
(Ethiopia) and from Baringo-Kapthurin Fm. (Kenya) might fall into this group or
ultimately prove to constitute a separate p-deme.

Irhoud. This p-deme is well-typified by adult cranium (no. |) and subadult
calvaria (no. 2) and mandible (no. 3); there is also an imperfect infant humerus (no.
4), all from the eponymous cave filling. Partial cranial and gnathic-dental remains
from Kebibat (Mifsud-Giudice quarry) may well represent the same or closely-related
p-deme. A fronto-facial fragment from Zuttiyeh (Galilee) is attributable to the same
demic group.

Florisbad. Although less complete than some other specimens, this partial cra-
nium is demonstrably distinctive, and in fact constitutes the type of the nomen, /e/mei
Dreyer. Other cranial specimens now known to be closely similar and hence attrib-
utable to this demic unit include Omo/Kibish-2 calvaria, Eliye Springs (ES-11693)
partial cranium, and Laetoli (Ngaloba) H.18 cranium, the latter the most fully-pre-
served of the lot.

KRM. This p-deme is based on fragmentary but varied cranio-gnathic-dental
elements and postcranial parts from several levels of SAS (Sands-Ash-Shell) Member
(up to 10 m, with MSA II industry) of Klasies River Mouth Main cave complex. The
complex is a single sedimentary depository subdivided spatially into Caves 1, 1C, 2,
1A, and adjacent 1B. Most remains derive from the lower such levels of Cave 1, with
fewer specimens from 1A (upper levels) and from 1B (basal levels); there is some
evidence to suggest most such specimens may well be of broadly comparable
antiquity. The MNI is at least 5. There is some evidence to suggest that fragmentary
maxillary parts (two individuals) from the lower and older LBS (Light Brown Sand)
Member of 1A represent an antecedent but related population. It can be argued, both
pro and con, that the hominin sample from Border Cave should best be attributed to
the same, or at least a closely-related, p-deme. | tend to support that view. Surpris-
ingly, requisite in-depth comparative morphometric studies appropriate to adequately
test this hypothesis have yet to be carried out. The same might be said in respect to
the (largely dental) samples from Die Kelders and Equus caves, and those vault and
teeth parts associated with MSA III industry at KRM-1A (South Africa) and from
Mumba shelter (Eyasi basin, Tanzania), respectively.

The Principal West Eurasian Hominin P-demes Are:

Dmanisi. The recent discovery in the Georgian Caucasus of a well-preserved
hominin mandible, with dentition, overlying the Mashavera basalt, with important
faunal and artifactual associations is a major contribution toward elucidation of the
peopling of Eurasia. The mosaic morphology of the single specimen, including its
derived characters in comparison with African counterparts, indicates its unique
p-deme status.

16 HOWELL

Atapuerca-Gran Dolina. Very recent excavations in the lower infill of the cavern
Gran Dolina of the Atapuerca (Spain) karstic complex has afforded unsuspectedly
ancient hominin occupation, just prior to the Brunhes/Matuyama paleomagnetic
reversal event. The occurrence in level TD-6, which includes an artifactual assem-
blage and faunal residues, comprises thus far cranial, gnathic, dental, and some
postcranial parts of some 5-6 hominin individuals, subadult and adult. Like the
associated mammal remains, there is evidence of breakage, impact fractures, and
incision marks, all suggestive of anthropophagy. The morphology, as thus far
revealed, is distinctive and seemingly quite divergent from less ancient European
counterparts. The sample, surely to be augmented in future excavations, merits
recognition as a new p-deme. An incomplete hominin calvaria from Ceprano (Sacco-
Lire basin, Latium), from a situation low in the known local succession, may well
prove on fuller study to constitute another representative of the group.

Mauer/Arago. Hominin remains from these localities constitute the next oldest
documented samples in Europe proper, to which now Boxgrove, Sussex (a tibial
diaphysis) may probably be added. The isolated Mauer mandible with dentition is
the type of the nomen, heidelbergensis Schoetensack. The Arago sample, comprising
cranio-facial elements, two partial mandibles, dentitions, and postcranial elements,
is best taken as basis of comparison. Overall this p-deme is distinguished by an
idiosyncratic (regional) mosaic of some (sym)plesiomorphic cranial, gnathic, and
postcranial features coupled with derived (apomorphic) features of other aspects of
cranium (fronto-parietal elements, facial skeleton) and mandible (symphysis and
ramus, dentition) which may approximate structures characteristic of subsequent
Neandertals. The extent to which fragmentary hominin remains from Italy — includ-
ing Fontana-Ranuccio (dentition), Visogliano-2 (mandible fragment), and Venosa-
Notarchirico (femoral diaphysis) — might reflect this or another related p-deme
remains to be evaluated.

Petralona/Atapuerca (Sima). This p-deme is among the best known and charac-
terized in the European mid-Pleistocene, initially as a consequence of the recognition
of the distinctive, beautifully preserved Petralona (Khalkidhiki) cranium, the type of
the nomen, petralonensis Murmill. More recently, the extensive hominin assemblage
of almost all major skeletal elements from several dozens of individuals recovered
from Sima de los Huesos, Atapuerca, has afforded the largest single hominin sample
from the mid-Pleistocene of Europe. This affords also a basis for fuller evaluation
and attribution of isolated or incomplete/damaged specimens (Montmaurin-La Niche
mandible, Vertessz6llés occipital and dental elements, and Steinheim, Swanscombe,
and Bilzingsleben crania) about which considerable discussion and indeed contro-
versy prevailed over too many years. The Steinheim specimen is the type of the
nomen, sfeinheimensis Berckhemer, and this of course has priority over petralonen-
sis. These examples, along with the still ill-known Apidima Diros (Greece) crania
and, perhaps, the recently found and remarkably complete Altamura (Italy) skeleton,
may ultimately prove to be attributable to the same demic group. Similarly, a diversity
of more or less fragmentary specimens from Italy — in Liguria, Prince Cave (innomi-
nate), in the Latium, Castel di Guido (cranial, femoral fragments), Cava Pompi

HUMAN FOSSIL RECORD Li

(postcrania, cranial fragments), Casal de’ Pazzi (cranial fragment), Sedia del Diavolo
(postcranial/cranial fragments), and Ponte Mammolo (postcranial fragment) — re-
quire comparative examination from this perspective. This p-deme reveals persist-
ence of some plesiomorphic features, but substantially stronger and widespread
expression of Neandertal synapomorphies.

Neandertal. This p-deme was the first pre-modern human form known in the fossil
record and is now, overall, the most fully and geographically extensively represented
hominin from western Eurasia. The first recognized example, a partial skeleton from
Feldhofer cave, Neandertal, is the type of the nomen neanderthalensis King. It is most
extensively documented in the Last Glacial ('*O Stages 4-3) from the Siberian Altai,
central (Teshik-Tash) and western Asia (Shanidar) into the Levant (Kebara, Amud,
Tabun, Dederiyeh), the Crimea, west Caucasus, and throughout the reaches of middle
and western Europe into the Apennine and Iberian peninsulas. Its earlier history 1s
documented in Stage 5 (Krapina, Saccopastore, La Chaise — Bourgeois — Delaunay,
Ganovce, Sala, Taubach, Salzgitter-Lebenstedt), Stage 6 (in France, Lazaret, La
Chaise — Suard, Fontéchevade, Biache, and in Wales, Pontnewydd), and even into
Stage 7 (Ehringsdorf). Partial or largely complete skeletons, some in definite inter-
ment circumstances, enable a very full, if not absolutely exhaustive, elucidation of
skeletal paleobiology. The distinctiveness of the p-deme, with extensive autapomor-
phic character states, throughout its spatio-temporal range, and including variability,
aspects of dimorphism, and ontogenetic development, is well-established and exten-
sively documented. There are overall phenetic resemblances, and sharing of particu-
lar discrete traits, with antecedent demes, particularly with the Petralona/Atapuerca
p-deme, but substantially less so with that of Mauer/Arago.

Skhul/Qafzeh. This p-deme is well-known, but only surely so from the epony-
mous Levantine cave localities of M. es-Skhul (Mt. Carmel) and Dyebel Qafzeh
(Galilee). These samples comprise partial or semi-complete skeletons, with associ-
ated skull parts, of 10 and 13 individuals respectively, including both adults and
infants. (An infant individual, No. 1, from the es-Skhul site is designated lectotype
for the species nomen palestinus McCown and Keith.) In cranial vault and facial
morphology, gnathic features, some dental characteristics, both ontogenetically and
in adults, and in varied aspects of postcranial (both axial and appendicular) morphol-
ogy and proportions, these samples differ consistently and substantively from Nean-
dertals and more closely approximate the //. sapiens condition, without however
replicating it. Some phenetic, and thus presumably genetic, affiliations with the
Maghrebian p-deme of Irhoud, of which a representative (Zuttryeh) is known in the
southern Levant, have been established. Potentially attributable to the Skhul/Qafzeh
deme is Tabun-C2 (adult mandible), which like the eponymous localities is associated
with a ‘C-type’ Mousterian of Levallois facies industry.

The Principal East Asian Hominin P-demes Are:

Yunxian. This stands, for the moment, as among the oldest documented hominins
in eastern Asia. It is represented by two relatively complete but substantially distorted

18 HOWELL

crania from Quyuanhekou, richly fossiliferous and artifact-bearing middle terrace
deposits, Han River (Hubei). So far as known this p-deme shares many (not all) of
the features characteristic of the Zhoukoudian p-deme, whereas others are attenuated
if expressed at all. The Gongwangling (Lantian, Shaanx1) partial calvaria, including
maxillary fragments, which is deformed with substantially altered surface relief,
shares features both with this deme and that of Zhoukoudian, in the former instance
thus apparently invoking a more plesimorphous state.

Zhoukoudian. This was the first major documentation of an extinct form of
humanity in continental East Asia. The essential sample, to which the nomen,
pekinensis Black & Zdansky applied, is the substantial hominin collection of Zhouk-
oudian-1 locality (Hebei), comprising some 45 individuals, 20% of which are
immature, largely represented by calvarial, gnathic, and dental elements, and only
few (14) and incomplete postcranial parts. The particular morphological distinctive-
ness of this deme is thus, overall, well-documented, and as a consequence it is a
central comparative focus for all subsequent additions to the Asian hominin record.
Thus, reputable records of the deme exist in other areas of largely northern/central
China in Shaanxi (® Chenjiawo, a mandible, holotype of the nomen, /antianensis
Woo), Shandong (* Qizian Hill), Henan (Xinghuashan), Hubei (Longushan, Builong-
dong, Longgudong), Anhui (* Longtandong), Kangsu (* Huludong) and Guizhou
(Yanhuidong). Many such samples compromise isolated or associated teeth, whereas
two (*) comprise cranial parts, another (*) an association of skull and postcranial parts
of some four individuals, and another (#) an isolated mandible (and, perhaps, the
oldest documentation so far of this p-deme).

Dali. This p-deme is represented, perhaps solely, by a well-preserved cranium
with displaced facial skeleton from ancient terrace gravels of the locality Tianshuigou
(Shaanxi), the name deriving from the eponymous county. This is the type of the
nomen daliensis X. Wu, proposed to accommodate this and some other purportedly
related specimens. This individual lacks some (not all) plesiomorphies and autapo-
morphies of both Yunxian and Zhoukoudian p-demes and, contrariwise, exhibits
derived features of both cranial vault elements, their proportions and conformations,
and, especially, distinctive reorganization of facial structure. Other localities which
might, conceivably, afford representatives of this deme could include Walongdong
and Guojujan (Hubei) and Chaoxian (Anhui), and perhaps also Dingcun (Shanx1);
however, comparative studies are still required to substantiate such an inference.

Jinniushan. This p-deme, apparently distinct from that of Dali, is represented by
a largely complete cranium (and dentition) and some associated axial and appendicu-
lar skeletal elements from the eponymous cave locality (Liaoning). Although as yet
only preliminarily described, this individual departs overall in significant aspects of
cranial vault and facial morphology from Dali, and thus exhibits a more derived
condition. It is unclear, as yet, the extent to which this structure is paralleled or
reflected as well in the Xujiayao skeletal series of cranial vault bones and teeth
(sampling some 10 individuals) from the Datong basin (Shanx1).

Maba/Hathnora. This p-deme was first documented in 1958 by the recovery of
a large hominin partial calvaria from a fissure fill in Shizi Hill (near Maba, Guang-

HUMAN FOSSIL RECORD 1S

dong). It is type of the nomen, mapaensis Kurth. Its divergence from the Zhoukoudian
morphotype, and otherwise purportedly archaic features, coupled with incomplete
condition, long obfuscated elucidation of its affinities. The recovery of another partial
calvaria near Hathnora, middle reaches of Narmada valley (Madhya Pradesh) from
a terrace fill conglomerate affirms the morphological features of Maba. (This was the
type of the nomen, narmadensis Sonakia.) Although unfortunately incomplete in
critical areas of the vault, and lacking facial skeletons, both are fundamentally similar
in total morphological pattern and exhibit a melange of primitive, derived, and unique
features. These diverge from those of Zhoukoudian, Dali, or Jinniushan p-demes, and
strongly suggest separate demic attribution.

The Principal Sunda Shelf Hominin P-demes Are:

Glagahomba/Sangiran. This designation is proposed for a poorly known (and
ill-appreciated) hominin considered here as a distinctive p-deme. The name refers to
a locality on the northern limb of the Sangiran dome (anticline) near which one such
hominin specimen (Sangiran-8 or B, imperfect mandible with dentition) is specifi-
cally provenienced. The initial (‘type’) specimen (Sangiran-6 or A, right mandible
fragment with some dentition; the lectotype of the nomen, palaeojavanicus von
Koenigswald) derived, ambiguously, from this same general area, and more particu-
larly to the north toward Brangkal. Another such fragment (Sangiran-5, reportedly
collected east of Kalijoso, and the holotype of the nomen dubius von Koenigswald),
of unspecified provenance, might also be attributed to this group, as has been one
(Sangiran-31) and/or another (Sangiran-27, cranial base and upper dentition) cal-
varial/cranial remains, the former from the central dome area. These several examples
have such a distinctive set of gnathic, dental, and vault morphologies and sizes,
strongly autapomorphic, as to set them apart from other peninsular p-demes, and
particularly that of Trinil/Sangiran.

Brangkal/Sangiran. This designation is proposed for a distinct p-deme, recovered
in the northern area of the Sangiran dome, as represented by the partial cranial remains
with maxillary dentition of Sangiran-4. This is the holotype of the nomen robustus
Weidenreich. Its salient characters and known total morphological pattern were
adumbrated fifty years ago. It is unclear whether isolated mandible portions with
dentition — Sangiran-1b (and maxilla fragment la) from south Bukuran (eastern
dome) and Sangiran-9 from near Tegopati/Wonolelo (northeastern dome) — should
be similarly attributed or not. This is also unfortunately the case in respect to the
Perning-| (eastern Java) infant calvaria, type of the nomen modjokertensis von
Koenigswald, and (perhaps) the oldest documented hominin on the Sunda Shelf.

Trinil/Sangiran. This p-deme is among the best represented of Pleistocene Javan
Sundaland hominins. The holotype, a calotte (Trinil 2), excavated from Trinil (Solo
River, east-central Java) is the source of the nomen erectus Dubois. Postcrania
(femora), also excavated, have been both deleted from (no. T-3) and associated with
(nos. T-6-9) this sample (which also includes a P;). However, the first specimen found
was an indeterminate mandible fragment from Kedung-Brubus, from which a femoral

20 HOWELL

diaphysis was subsequently recognized. Anticlinally deformed lahars, volcaniclas-
tics, and fluviatile sediments of Sangiran dome afford the largest single demic sample
from this region — cranial elements (14, including two crania, two natural endocasts,
nine gnathic elements with dentition), isolated teeth, and uncommon postcrania (1+),
in an incomplete listing. The sample is distinguished by its extensive hyperostosis
and suite of autapomorphic character states.

Ngandong. This p-deme is represented by the substantial excavated hominin
sample from the eponymous locality of the central Solo river. It comprises five cranial
vault elements and nine partial or more complete calvaria, adult and subadult, and
several postcrania (tibial diaphyses, innominate fragment). This constitutes the type
of the nomen so/oensis Oppenoorth (of which a calotte, Ngandong-1, is the holotype).
Two other localities of this drainage, Sambungmachan (a meander between Trinil
and Sangiran) and Ngawi (east of Trinil), have each yielded a calvaria (and the former
also a tibial diaphysis) attributable to this deme. It shares the same fundamental
morphotype of the Trinil/Sangiran p-deme, associated with some derived states of
calvarial size, proportions, and shape.

Of these twenty or so distinguishable p-demes only three have not received
categorical ranking at some time and thus do not bear specific or subspecific nomina.
Such recognition reflects, usually, the predominantly typological approach tradition-
ally prevalent in human paleontology and the mind set to which Simpson directed
attention. It led Ernst Mayr (1950) to recognize that two circumstances have attended
such nomenclatorial plurality: “a very intense occupation with only a very small
fraction of the animal kingdom which has resulted in the development of standards
that differ greatly from those applied in other fields of zoology .. .” and “the attempt
to express every difference of morphology, even the slightest one, by a different name
and to do this with the limited number of taxonomic categories that are available.”
Mayr (1950) then suggested several ‘practical rules’: “not to assign a formal name to
any local population or race that does not deserve subspecific rank”; “give trinomials
to all forms that do not deserve higher than subspecies rank”; and “to group together
as subspecies groups all those subspecies within a species that form either geographi-
cal or chronological groups.” After such practical admonishments, he then unfortu-
nately suggested that humankind “speciated only once if our assumption is correct
that never more than one species of man existed on earth at any one time,” thus laying
the theoretical groundwork for the so-called ’single-species hypothesis’ which ulti-
mately confounded human evolutionary studies for nearly fifteen years. Since the
corollary to this perspective was that, in this view, “the known diversity of fossil man
can be interpreted as being the result of geographic variation within a single species
of Homo,” the stage was similarly set for the promulgation of the so-called ‘Multire-
gional Evolution’ model (or hypothesis), the roots of which extend back, via
Dobzhansky (1944), some fifty years at least. Perhaps the single strongest longtime
supporter (as successor) of this perspective was the late J. N. Spuhler (1993:291; also
1985, 1988, 1989) who considered that “the combined morphological, archaeological
and molecular information explains the origin of modern humans by regional evolu-

HUMAN FOSSIL RECORD 21

tionary transformation with continual unification of species by gene flow and local
isolation by distance.”

Over the past several decades multivariate statistical methods have been increas-
ingly adopted in biological anthropology, and have come to play as well a prominent
role in both analytical and comparative studies of the hominin fossil record. Thus,
almost all of the aforesaid hominin p-demes, or at least some of their constituents,
have been variously subjected to such treatment, often in conjunction with other such
analyses of diversity and degrees of phenotypic similarity and divergence reflected
among modern human populations. Table | (see Appendix A) is a non-exhaustive
inventory of such studies, their foci, and the principal procedures employed.

The significant outcome of the totality of such studies is, according to the
appropriateness of the procedure(s) and scope of morphometric parameters em-
ployed, that the distinctive character of particular samples has been well-delineated
and verified, and the phenetic (and thus, inferentially, phylogenetic) affinities rea-
sonably quantitatively elucidated. Moreover, the diversity exhibited by spatio-tem-
poral samples of known hominin p-demes is unparalleled among samples of modern
human populations, in which diversity is low whether assessed by morphological
variability or conventional genetic markers. Thus, “the most mitochondrially differ-
ent humans known are less different even than the only two siamangs sequenced to
date or than lowland gorillas living in a restricted area of West Africa,” and such
“limited genetic diversity becomes equivalent via application of the molecular clock
to a recent time for the mitochondrial ancestor of living humans. . .” (Ruvolo ef al.
1994:8903; Ruvolo et a/. 1993). Interpopulational heterogeneity is greater in mtDNA
than in nDNA in modern humans; the mutation rate and probability of fixation is
some ten times higher in the former. Thus, the mean numbers of nucleotide substitu-
tions (D-loop region) between pairs of individuals within populations 1s 0.0469 (vs.
0.165 in chimpanzees), and that between populations is 0.0525 (vs. 0.140 in chim-
panzees). Most human diversity (some 85%) is of course expressed polymorphically
(within populations) rather than polytypically (between populations) (Lewontin
1972). Thus, p-demes are both informative and problematic from an actualistic
perspective.

Modern Human Origins and the Pattern
of Later Hominin Evolution

A number of estimates (Table 2, Appendix A) of the age of a modern human
ancestor (cf. Long 1993) have been made, both from classical genetic markers
(proteins, blood groups, etc.) and from mtDNA (either control region or coding
sequences) lineage coalescence projections. The latter affords a measure of amount
of evolutionary change along a lineage; extent of divergence between two lineages
may also be evaluated (and is twice the former value). There is congruence in analysis
of divergence according to several different analytical (statistical) procedures em-
ployed (MP, NJ-BS, UPGMA), although rooting of trees has sometimes afforded
problems and attendant controversy. Recently additional evidence has been afforded

22 HOWELL

by analysis of gene sequences of the (paternally-transmitted) Y chromosome (Paabo
1995). All such estimates afford mean ancestral ages in a range between a hundred
thousand to as much as half'a million years ago, dependent on the time of ape (Pan)
and hominin divergence. A maximum age would reflect genetic divergence rather
than (usually subsequent) population divergence. A mean value between those
extremes, of 250 + 50 Ka, is as reasonable an approximation as might now be
expected. African populations exhibit maximum sequence divergence, and more
divergent mtDNA lineages (enhanced heterozygosity). There are contrary results as
to the order of subsequent differentiation of European and Asian populations.
Aboriginal Amerindian populations exhibit least mtDNA diversity, and that diversity
comprises a subset of Asian mtDNAs, of markedly altered frequencies. All genetic
evidence, from whatever source, unequivocally fails to project modern human roots
into deep Pleistocene time. These include classical (protein) genetic markers, NDNA
(RFLP) markers, microsatellite loci, Alu insertion (and STRP) polymorphisms, and,
of course, mtDNA. Thus, there is a principal constraint against any phylogenetic
formulation that posits prolonged anagenesis in the modern human (Homo sapiens)
lineage and, correlatively, protracted histories for presumptive subspecies. This is
wholly corroborated by the documented evolutionary history of other mammalian
taxa, as, for example, Groves (1992) demonstrates.

Demes that make up populations, and populations themselves, are ephemera
(“individuals and groups are like clouds in the sky or dust storms in the desert”;
Dawkins 1989:34-35). Or, as Futuyma (1987:467) expressed it, “in the absence of
speciation, much of the geographical variation we observe is ephemeral, leaving little
imprint on evolution in the long term. This 1s chiefly because most local populations
are ephemeral; over even moderately short spans of evolutionary time (tens or
hundreds of thousands of years), the habitats to which populations are adapted shift,
often over long distances, in consequence of climatic change. The most recent
dramatic instance . . . is seen in the Pleistocene, during which the distribution of both
temperate and tropical species changed markedly and repeatedly. . . .” In fact
Futuyma’s (1987:465) purpose was to "propose that because the spatial locations of
habitats shift in time, extinction and interbreeding among local populations makes
much of the geographic differentiation of populations ephemeral, whereas reproduc-
tive isolation confers sufficient permanance on morphological changes for them to
be discerned in the fossil record."

In fact, are not subspecies — aggregates of geographically-delimited population
clusters — similarly ephemeral? Subspecies are not units of evolution, have an
arbitrariness in respect to their recognition and delineation, and are customarily
considered of limited classificatory value, despite being accepted as “a genuine
taxonomic category based on populations,” when in fact “no nonarbitrary criterion
is available to define the category subspecies nor is the subspecies a unit of evolution
except where it happens to coincide with a geographic or other genetic isolate” (Mayr
& Ashlock 1991).

A focus on p-demes and on their spatio-temporal linkages (or lack thereof) allows
avoidance of the vagaries of subspecific attributions and enables a more immediate

HUMAN FOSSIL RECORD 23

evaluation of the smaller units that participate in evolutionary processes. Such
examination strongly suggests that such units, and as well the attendant larger
subspecific groups of which they were evidently a part, were evolutionary ephemera.
P-demic continuity is sometimes patently demonstrated, but such is far from always
the case, and both punctuations and disjunctions/discontinuities are evidenced even
among the limited (less than two dozen) demic instances recognizable after only five
generations of research. Thus, even the near future promises to afford both further
documentation of known demic units as well as evidence of those as yet wholly
unknown.

Lahr (1992; also 1994) examined the assertion that sets of hominin cranio-dental
features, considered by some as characteristic of the phyletic evolution of regional
populations from local (archaic) antecedents, regularly exhibit higher incidences in
such regions. In fact, whereas many features (of which 30 were extensively analyzed)
“present a regional pattern, this pattern does not always correspond to that proposed
by the model,” and she found some even “occur in other populations with a higher
frequency” (Lahr 1994). Thus, “these features do not support a multiregional origin,
giving further support to the existing fossil, chronological and genetic evidence for
a single African origin of all modern humans.”

Waddle (1993, 1994) has recently examined, through matrix correlation tests,
expected versus actual morphological distances, according to several phylogenetic
models, between antecedent and succeedent hominin samples of mid- to late-Pleis-
tocene age from Europe, western Asia, and parts of Africa. The basis of evaluation
comprised 165 cranial characters/parameters, including discrete traits (52), angles
(39), and metrics (74). Her “quantitative analyses . . . support a single origin for
modern humans as opposed to continuous long term evolution within regions.” She
concluded that “models that hypothesize worldwide gene flow in opposition to
evolutionary continuity explain observed fossil variation only if continuity is a
relatively weak force compared with gene flow.” Thus, her “results support the
gradistic notion that coterminous taxa tend to be similar in morphology . . ..” but “do
not support the idea of evolutionary continuity within regions as indicated by the
persistence of specific cranial features.” This analysis, as many others before, “clearly
refutes evolutionary continuity in Europe, and for the Neanderthals of southwest
Asia.” It demonstrates that a “single African origin model provides a better explana-
tion for the cranial variation described in the [actual] morphological distance matrix
...” (Waddle 1994). This conclusion is wholly in keeping with the substantial body
of a diversity of genetic evidence pointing consistently in the same direction (Nei
1995).

Lieberman (1995:192) has stressed that the “choice of characters poses the greatest
obstacle to resolving evolutionary relationships among human taxa.” Characters must
be rigorously evaluated and ultimately chosen on the basis of homology, demonstra-
ble shared-derived polarity, and universality in occurrence across hypodigms, with
attendant delineation and definition of character state(s) and consistency in scoring
methods. It has been posited (Frayer et a/. 1993:21-22) “that combinations of features
with differing frequencies diagnose groups in the past, just as they are important in

24 HOWELL

forensic diagnoses of racial identification.” | concur, however, with Lieberman
(1995:166) that this “argument that regional human clades are best characterized by
combinations of derived and primitive characters rather than any specific derived
characters is illogical,” as in fact, minimally “only one real shared-derived character
is needed to demonstrate common ancestry.” Lieberman’s useful examination of
some 33 characters often employed in such studies, of which “30 features [were]
proposed by Frayer ef a/. (1993) as regional shared-derived characters (synapomor-
phies) shows that most (87%) clearly do not support polycentric evolution [regional
continuity] and many (27%) support the RA [recent African origin] hypothesis”
(1995:176). Nonetheless much remains to be elucidated in respect to the develop-
mental and ontogenetic aspects of characters and character complexes and the
co-associations and interrelationships among them.

Some knowledge of essential demographic parameters is critical in the evaluation
of models of hominin phylogenesis (Weiss & Maruyama 1976). However important,
this is perhaps the single most unknown aspect of the hominin past, for which
inference and speculation afford only limited insight. The foundation for such study
was set out largely by F. A. Hassan (1981), and it is fair to say that there have been
only limited advances subsequent to his remarkable effort, at least in respect to
Pleistocene deep time. Moreover, parameters surely varied in the course of the
Pleistocene, and thus inferences derived from extrapolations from the demographics
of recent foraging peoples may well have only limited relevance and applicability to
those most ancient hominin taxa within genus Homo. However, general principles
and maximal parameter values may afford some basis for argumentation. Table 3 (see
Appendix A) sets out some estimates of Pleistocene hominin population parameters.

The (maximal) vital rates, as estimated for late Pleistocene hunter/foragers, are as
follows (Hassan 1975): (a) birth interval = 22 months; (b) live birth interval (allowing
fetal death and sterility at 12%)=27-30 months; (c) female reproductive span
(allowing reproductive capacity — nubility — at 16 years, and adult female longev-
ity equal to 29 years) = 13 years; (d) live births/adult female [allowing for 10%
maternal mortality and above parameters b and c] = 4.7 offspring; (e) surviving
offspring/adult female (allowing infant mortality 50%) = 2.35 offspring. Annual
population growth rate (allowing generation span of 24 years and life expectancy
(after 15) as 17-18 years) is estimated at 0.73%. Subsequently, Hassan (1981)
suggested a downward revision of this value to 0.011%. Some quite different
parameters may be expected for earlier time spans in the Pleistocene and among such
different p-demic taxa. Overall, life span is short, there is a prolonged offspring-spac-
ing interval, and a low rate of child survivorship prevails.

A series of principles emerge from such vital rate parameters, given the demo-
graphic structures of foraging peoples. Overall populations are very small to small.
Isolates, composed of family units, bands (of about 25), and demes (of about 500),
are small overall and semi-continuously or discontinuously (parapatrically) distrib-
uted spatially (broadly corresponding to an ‘island’ or ‘neighborhood’ model).
Population densities are low. Disjunctive distributions between larger population
aggregates are both effected by density factors and ratio of food yield to energy cost

HUMAN FOSSIL RECORD 25

and constrained by paleoclimatic/paleoenvironmental changes which impact associ-
ated habitats. Populations are largely in a state of equilibrium, with low to extremely
low (arithmetic) growth rates (r), largely a balance between fertility and mortality
rates, and thus characterized by minimal growth in numbers and, correlatively, very
slow geographic expansion. Following the values posited in Table 3, doubling time
(Dt) approximates a million years (990 ky) in the earlier Pleistocene. This approxi-
mation might well seem excessively slow considering the consequences of range
extension and population growth attendant upon expansion into new (Eurasian)
latitudes and habitats. Intermediate and thus elevated values between this excessively
slow rate and the accelerated growth in the Late Pleistocene surely must have
prevailed between ~1.0-0.25 Ma. In the Middle Paleolithic, Dé is substantially
accelerated (128 ky, 6400 generations), and in the Upper Paleolithic it rises markedly
to 6.3 ky (minimally 310 generations, at 20 years/generation), or some 20 times faster.

The distribution of pair-wise genetic differences, exemplified by mtDNA mis-
match distributions, are directly relevant to population size parameters (Slatkin &
Hudson 1991; Rogers & Harpending 1992; but compare Marjoram & Donnelly
1994). These reflect the number of nucleotide site differences between each of any
pair of individuals. Differences among sequences within a population are mismatch
distributions; differences among sequences from different populations are intermatch
distributions (Harpending et a/. 1993). A smooth unimodal or wave-shaped curve of
aggregate distribution reflects ancient population growth, and its position on a scale
of number of sites exhibiting differences between samples reflects timing and
magnitude of growth (the curve peak corresponding to the maximum concentration
of coalescent events). The presence of substantial variability in mtDNA trees among
modern humans is a reflection of a “relatively recent expansion in size” of such human
populations (Rogers & Jorde 1995). Elucidation of such population growth is enabled
by knowledge of mutation rate (uw, estimated at 2% or 4%/10° years); female
population size prior to (No) and consequent upon (V,) expansion; time (/) in
generations (since expansion) and time (7) since expansion in units of 1/(2u)
generations. The several divergence rates afford population expansion ages between
(T) 33-75 Ka (at 4%, uw = 1.5 x 10°), or 200 generations, and (7) 66-150 Ka (at 2%,
u=7.5 x 10), or 4250 generations. The Np is considered as < 7 x 10? and N, as at
least 1.50 x 10° (hence a breeding population of ca. 3 x 10°), based on an assumption
of random mating. If, on the other hand, populations were geographically structured,
as seems quite likely, then initial population was only a fifth as large (some 1,500
females) and the post-growth population less (ca. hundred-fold).

The pattern of intermatch (i-m) distribution (between populations) may be broadly
(or closely) coincident with a mismatch (m-m) distribution (within a population).
Rogers & Jorde (1995; Rogers 1995) consider that “this pattern suggests that an
expansion [in population] either preceded or coincided with the separation of these
populations.” However, and not uncommonly, an intermatch distribution may pre-
cede diagrammatically (= antecede temporally) a m-m distribution, suggestive of an
intervening interval of 30 up to 50 ky. This situation is suggestive of either of two

26 HOWELL

explanations, each depending upon population structure, gene flow, and subsequent
growth: (a) an initial, broadly panmictic population splits, with weak or absent gene
flow, producing the i-m distribution, subsequent to which bottlenecks (or expansions)
result in differing m-m distributions within the derivative populations; or (b) sub-
populations of a larger population, linked by only weak gene flow, are largely
separate, producing an i-m distribution wave, and with mutual subsequent expansion
derive distinctive m-m distribution. The essential point 1s that “there is good reason
to believe that the major human populations separated long before the expansions
that are reflected in the within-group waves” (Rogers & Jorde 1995:12). In any case,
initial populations are small, some 1,500 (breeding) females, and are characterized
by subsequent (substantial) growth, thus reflecting a bottleneck situation (see also
Maynard Smith 1990; Wills 1990).

Ayala (1995) considers that “the theory of gene coalescence suggests that . . .
human ancestral populations had an effective size of 100,000 individuals or greater,”
and that “molecular evolution data favor the African origin of modern humans, but
the weight of the evidence is against a population bottleneck before their emergence.”
In his most recent evaluation Takahata (1995) asserts that “all studies of human
mtDNAs... suggest that the coalescence time is shorter than 0.2 my (10* generations)
definitely much shorter than | my (5 « 10* generations),” that “the mtDNA diversity
in the current human population was generated during the late Pleistocene,” and that
population (NV, values) fluctuated in the Pleistocene such that bottlenecks were real
and important, and “local human populations underwent frequent extinction/restora-
tion because of increased dispersal and adverse environmental conditions in the Old
World.”

Pairwise comparisons and, in fact, “all available genetic evidence is consistent
with the proposition that the major [modern] human populations separated from a
small initial population roughly 100,000 years ago and that most of these separate
populations experienced a bottleneck, or an episode of growth several tens of
thousands of years later” (Rogers & Jorde 1995:32). Harpending ef al. (1993:494,
see also Harpending 1994a, 1994b) concluded that “our results show that [modern]
human populations are derived from separate ancestral populations that were rela-
tively isolated from each other before 50,000 years ago. Major population expansion
took place between 80,000 and 30,000 years ago — 80,000 years ago in Africa and
perhaps 40,000 years ago among the ancestors of the Europeans.” And, “the existence
of between-group differences far older than within-group differences implies that the
late Pleistocene expansion of our species occurred separately in populations that had
been isolated from each other for several tens of thousands of years” (Harpending e¢
al. 1993:495). More specifically humankind appears to have expanded from an initial
size of some 10,000 (breeding) individuals to, at the least, thirty times that number.
This is far below several population estimates for the Late Pleistocene, which range
between 7 and 20 times greater. It is posited that a still smaller source population
comprised minimally 1000 breeding individuals. Distinctive, small human popula-
tion aggregates (subspecies = ‘races’) existed prior to their individual growth expan-
sions. These perspectives afford no support to a continuity (so-called Multiregional

HUMAN FOSSIL RECORD 27

Evolution or Regional Continuity) model of hominin evolution, but they are consis-
tent with a variety of recent (and African) replacement models.

Given small overall population size and low population density it is necessary to
consider the distribution and arrangement of populational groupings. This entails the
relationships between local (or minimum) bands (~ 25 individuals) to those of larger
aggregates (maximum bands or demes, connubium or dialectical tribe of authors) and
their arrangement and spacing in habitats. Some associated parameters include the
exploitative range and minimum equilibrium size (MES) in regard to mating net-
works. The ‘catchment territory’ (or home range) is based on area of economic
exploitation in respect to (radial) walking distance from home base, the latter
commonly being 10 km and the former ~ 314 km? (Hassan 1981). Areas will vary in
extent substantially in relation to population density (thus, 164 km? for 0.15 individ-
ual/km? for Hadza, and 6450 km? for 0.01 individual/km? for Caribou Eskimo). An
MES of band aggregates (maximum band of Wobst), which reflects the size of a
sub-population that can constantly afford members of a population with mates upon
reaching maturity, has been assessed as 175-475 individuals (= 7-19 minimum bands)
(Wobst 1974, 1976), thus maximally approximating demic size. These might com-
prise a maximally effective hexagonal matrix, with variable number of tiers of
minimum bands, or a more linear arrangement (with correlatively enhanced distance
between groups). Hassan (1981) considered ‘regional groups’ to comprise upwards
of a thousand individuals and Africa plus Eurasia as having some 6,000 groups in
‘Upper’ Paleolithic times, and only some 1,200 groups in ‘Middle’ Paleolithic times.

The overall population sizes and associated densities projected by several authors
(Table 3) are consistent in stipulating remarkably small population sizes, small
regional population aggregates, very low densities, and extremely slow rates of
population growth, particularly so within the mid- and earlier spans of the Pleistocene.
Such parameters, probably coupled with very limited rates of range extension into
virgin domains, initially including unoccupied latitudes of Eurasia, must be ade-
quately acknowledged in any models of later hominin evolution. If an extra-African
dispersal occurred broadly coincident with the Olduvai (N) subchron (~ 2.0-1.75 Ma)
—equivalent to the ultimate cold (boreal to tundra)-to-warm/temperate climatic
cycle of the Netherlands (late) Tiglian chronostratigraphic stage — that event 1s
coincident with the appearance and most of the span of African Homo ergaster, the
Dmanisi occurrence (Georgian Caucasus), an artifactual situation at Erq el Ahmar
formation (Jordan rift), and, at the younger end, perhaps ancient hominin penetration
into the Sunda Shelf. At the older end this would be broadly coincident with an
interval of enhanced aridity across equatorial African latitudes, as documented in
oceanic and continental sedimentary records. Such an event might thus attest to
dispersal, through range extension and population fission (demic budding), into the
southern tier of Asia, prior to any hint of penetration into Europe proper (from which
a number of appropriate fossil-bearing localities are known), or into middle latitudes
of central and eastern Asia. The latter area witnesses such penetration at most half a
million years later.

The single parameters set out (Hassan 1981:189; also 1980) for the source of such

28 HOWELL

an event (though not so intended) would posit population size of some 400,000 (some
800 demes of 16,000 bands) and density of 0.020/km’; an inhabited area of some 20
x 10°km/? is also posited. The latter value encompasses some two-thirds of the African
continent and thus might appear inordinately high. Some approximate estimates (in
10° km?) of major recent African biotic subregions are Saharan (6), Sahelian (3),
lowland tropical forest (2), and savanna/grasslands (15). The extent of the first and
third subregions, in terminal Pliocene time, are perhaps most critical to the question
of habitability and hence to estimates of population distribution and inferences of
population density. Their extent changes in accordance with low deep-sea tempera-
tures and enlarged global ice-volumes, and within the time in question would have
been influenced by planetary obliquity forcing, with substantial attendant displace-
ment southward of biozone boundaries. The dearth of direct archeological documen-
tation, either at all or in some acceptable geochronological context, sorely limits
explicit reliance on that resource. Nonetheless an overall initial distribution between
15°N and 30°S is reasonably approximate, but with demes and their inclusive regional
groups, 400 in all by Hassan’s estimate, concentrated about riverine and lacustrine
basin hydrogeographic regimes, effectively tethered as hominins must be, and thus
often of quite disparate and disjunctive distribution. Consequently, it is rather more
likely that overall distribution (inhabited area) was only a half or so as large as posited,
that total population was substantially less than posited (half as large, perhaps), and
that populations were markedly discontinuously distributed due to various resource
limitations.

Further, there is the question of human populations of later (mid-Pleistocene)
antiquity and the relevance of demographic parameters to questions of modern human
origins:

Only when gene exchanges occur frequently among local populations and the total
number of breeding individuals in the whole population is kept as small as about 10,000
does the multiregional hypothesis become compatible with the estimated age of the LCA
{last common ancestor] . .. However, it is difficult to explain how such a small number
of individuals could occupy vast areas of Africa and Eurasia over the last | myr while
maintaining an evolutionary status as a single species. A more likely explanation Is that
the age of the LCA indicates that modern humans originated much less than | myr ago
without integrating the substantially diverged H. erectus genes. This, together with the
premise that the genetic diversity in the oldest parental population is greater, provides
support for the recent African origin of modern humans. (Horai ef al. 1995:536.)

It has been noted before that world population for pre-modern humans has been
estimated (by Hassan 1981; also 1980), on the basis ofa diversity of parameters drawn
from hunter/gatherer analogues, as 1.0 + 0.2 x 10°. There have been no real efforts
to individualize size estimates, much less density evaluations, for Africa vs. Eurasia.
As there are correlative environmental changes in subtropical and tropical latitudes,
consequent upon changes in global ice volume and deep-sea temperature, particularly
attendant upon eccentricity modulation since 0.9 Ma producing one hundred thou-
sand year paleoclimate periodicity, it might be argued that Eurasian populations
waned when African populations waxed and vice versa under the impress of such
glacial/interglacial regimes. Any model of population size requires appropriate
elaboration and incorporation of such parameters.

HUMAN FOSSIL RECORD 29

Various estimates have been proposed from the perspective of population genet-
ics, with particular reference to mtDNA coalescence, mismatch (nucleotide substitu-
tion) differences, and simulation studies. Among the lowest such (restricted) values
are those of total N (source population) of < 3,000 individuals and N. female of 40-600
individuals (Sherry et al. 1994). Similarly, N = 1.25 x 10° and N. female of ~2.5 x
10* was posited by some of the same authors (Harpending ev a/. 1993). In their further
elaboration of the same model, considering initial (Np) and post-expansion (N,)
parameters, values of less than 7,000 (perhaps 5,000) No female and 150,000 N,
females (thus, N. of ~ 300,000) were posited under random-mating (panmictic)
circumstances. In a much more likely geographically-structured situation the respec-
tive values were Np females = ~ 1,500 and N, females = 150,000. Takahata (1991,
1993a, 1993b) considered that the effective (N.) population size, since the lower
Pleistocene, probably averaged 104 (perhaps 10°, considering evidence from Mhc).
However, if overall population is some 107 then the total N,, (number of breeding
individuals/populational unit x number of sub-populational units) is considered as
~10° (Takahata 1994). There is reason to believe that there has been “frequent
extinction and recolonization (turnover) of subpopulations in the lineage leading to
modern humans,” due to relatively small local human populational differentiation,
and the values that must thereby obtain between posited V. and values of N and n
given total population approximating a million. (It is apparent that sub-populations
with reduced N “are more liable to extinction,” and also that such values will be
affected by the viability of groups as reflected in 1.) Such circumstances could well
attend substantially enhanced deterioration of environmental conditions and their
attendant effects on life ways, on intensive adaptations in locales to localized
resources, and to restriction of gene flow between increasingly discontinuously
distributed subpopulational units.

In conclusion, I again cite Takahata (1991:594) in respect to population parame-
ters and gene flow among Pleistocene hominins, with particular respect to modern
human origins:

If... mutant genes, that might be responsible for the evolution of 1. sapiens, were
favored in any deme, they would spread over the entire population with high prob-
ability... However, the required time depends strongly on the interplay among various
population parameters . . ., and if the multiregional hypothesis assumes a large number
of demes and Nm < 0.1, it is unreasonable to think that even such favorable mutations
could spread over the entire human population during the Pleistocene. (NV = effective
size of each deme; m = per generation mutation rate)

Epilogue

On an empirical level, human evolutionary studies in recent years have shown
substantial progress and enhanced vitality. They have been especially marked by
greatly expanded documentation of the hominin fossil record, now to ~ 5 Ma,
recovery of representatives of hitherto unknown taxa, and enlargement of various
p-deme samples. In a number of instances, sophisticated in-depth study of various
aspects of skeletal biology, including seminal studies of growth and maturation, have
afforded requisite morphological profiles of newly recognized taxa and much ex-

30 HOWELL

panded knowledge of variability and other parameters of evolutionary biological
relevance in previously recognized, but insufficiently documented or studied, groups.
The elaboration and application of a diversity of geochronological methods, some
only in the last decades, have significantly impacted age assessments and correlations
of local, provincial, and regional fossiliferous/archeological occurrences and succes-
sions. The development and refinement of the GPTS, in conjunction with such
geochronological efforts, in both deep-sea and continental sedimentary records, has
afforded a hitherto unenvisioned time scale for temporally circumscribed late Ceno-
zoic global events. At more local, even locality-specific levels, there has been greatly
enhanced concern with stratigraphic, micro-stratigraphic, pedological, and related
studies relevant to elucidation of paleogeographic circumstances at increasingly
refined levels of analysis, such that efforts at paleo-‘landscape’ recognition and study
can be considered feasible and even fruitful. Taphonomy, the roots of which extend
well back into the previous century, has expanded vigorously in keeping with these
developments, and archeological studies have become an integral part of the emer-
gent paleoanthropology endeavor. Paleoenvironmental investigations have increased
remarkably in scope and in depth, in the perspective of newly formulated chrono-
stratigraphic frameworks, and in relation to developments in paleoclimate analysis,
simulation, and modeling and broad applications of palynological and isotopic
analyses.

The study of modern human populations was increasingly encompassed within
the span of population genetics upwards of forty years ago. However, the focus on
traditional genetic markers was largely employed toward the purported elucidation
of relationships between populations (especially sub-racial units), as well as aspects
of adaptation and population structure and demographics; it was relatively strongly
classificatory in many instances. There have been, of course, notable exceptions, and
concerns with population histories in sub-recent time are repeatedly evidenced in the
work of some human population geneticists, particularly L. L. Cavalli-Sforza and M.
Nei, but including also those more immediately affiliated with biological anthropol-
ogy. Moreover, a major impact has clearly been through investigations directed at
the elucidation of phylogenetic relationships within primates, particularly within
Hominoidea. Increasingly, nDNA and mtDNA have become the focus of such efforts,
and this has led to renewed and redirected concerns with ascertainment of popula-
tional affinities, with branching relationships, and ultimately with the origins of
modern humans (Homo sapiens). It is of some interest that, in the latter case, studies
have been pursued very largely independently, rather than cooperatively and conjoin-
tly, by those investigators in population genetics/molecular biology and those in
human paleontology. Joint authorship by such practitioners is almost unknown. This
is not to deny that researchers have sought to follow and be current with the nature
and consequences of others’ research endeavors, although competences across this
span are scarcely to be expected or even conceivable. The overt lack of cooperative
endeavor is not exemplary, and the need for conjoint research and resultant publica-
tion is patently manifest. The burgeoning interest in the evolutionary history of

HUMAN FOSSIL RECORD 31

humankind, from paleontological, behavioral, and genetic perspectives, demands
closer affiliations between concerned investigators.

There would appear to be some gap or lack of congruence between developments
of an empirical sort and their theoretical evaluation. This is, likely, a problem both
ontological and epistemological. It has, surely, direct bearing on approaches to and
perspectives on the evolutionary process within the hominin clade, and most espe-
cially conceptions of genus Homo, its origins and evolutionary history. It is probably
true that an encompassing scenario of hominin evolution is beyond our grasp, now if
not forever. Similarly, models and hypotheses of hominin diversification, including
that of origins of genus Homo and of modern humans, are all surely incomplete, and
some still more seriously flawed. All ‘hard’ formations of hominin phylogenesis are
controversial and have been, and are being, subjected to severe criticism. The
polycentric, so-called ‘candelabra hypothesis’ (sensu C. S. Coon) was effectively
moribund upon its formal exposition, as was soon recognized by some (surprisingly
not all) evolutionary biologists. The so-called ‘Noah’s ark’ formulation has been
presented in several guises (with catchy monikers), including ‘Garden of Eden’ and
‘African Eve’, and the less euphonic expressions of RAO theory (Recent African
Origins), AHRM (African Hybridization/Replacement Model), and AOAM (African
Origins/Assimilation Model), the latter two of which explicitly permit or claim some
levels of inter-demic or higher level hybridization. All have their varied, usually few
(if nonetheless vocal) adherents, and each has been somehow negatively evaluated
by contrary opponents and several independent and more detached scholars (Aiello
1993; Lewin 1993).

An MRE (Multiregional Evolution, or Regional Continuity) model has been
proposed (Wolpoff er a/. 1984) and subsequently elaborated (Wolpoff 1989), pur-
portedly as a null hypothesis subject to testing and falsification against such other
models. It was originally put forward “as an attempt to show how the specific pattern
in a polytypic species can be explained as a consequence of modern clinal theory”
(Wolpoff er al. 1984:450). Its proponents sought to account, in genus Homo, for (a)
morphological contrast between a central, source population and peripheral, deriva-
tive populations; (b) appearance early on of so-called ‘regional continuity’ features
peripherally by comparison with the purported appearance, substantially later, of
other such features centrally; and (c) the establishment and persistence of such
presumed peripheral vs. central contrasts subsequently. This formulation grew, in
part, out of a ‘center and edge’ hypothesis that reflected reduced (or minimal)
polymorphism at the periphery ofa species’ distributional range such that, in the case
of East Asian Pleistocene hominins, there were “peripheral populations with intrare-
gional homogeneity and interregional heterogeneity” (Wolpoff et a/. 1984:450). A
trend toward peripheral monomorphism was taken to be a consequence of “continued
drift in small populations, founder, and peninsula (bottleneck) effects,” and with
adaptive divergence a consequence of environmental plus random drift effects.

The MRE model is, in fact, as much or more a scenario as an explicit, testable
hypothesis. It has sought to encompass pretty much all, without actually explaining
much of anything. In any case, this scenario, at least applied to evolution within genus

32 HOWELL

Homo and modern human origins in particular, is seriously flawed, even in respect
to its presumptive reference basis in the hominin fossil record. Since its more formal
proposal and subsequent proclamation (e.g., Frayer et a/. 1993) in a consistently
‘hard’ form by a varying coterie of proponents, it has emerged as a fragile, frayed,
and unfructuous conceptual framework. It is now largely bankrupt and can be, and
has been, rejected on innumerable grounds, including various aspects of population
genetics, demographics, paleogeography, archeology, and, indeed, the hominin fossil
record itself. It has presumed, at least by implication, the highly questionable
existence of a limited number of primeval regional populations, now considered by
proponents as already sapiens and thus within which are to be found, perhaps
incipiently, the sources (roots) of all modern human diversity. In this regard, | concur
with Marks’ perspective (1995:193) that:

There is no evidence for a primordial division of the human species into a small
number of genetic clusters that are different from one another. The fact is, we do not
know how many basic groups of people there are, and it is very likely that there are no
small number of groups into which a significant proportion of the biological diversity
of the human species collapses.

MRE requires that natural selection drive African and African-derived hominin
populations in Eurasia anagenetically and ineluctably toward the modern human
condition. It has an almost omega-point inevitability about it. This is ultra-Darwinian
in its most extreme sense (Eldredge 1995), and is difficult to conceptualize in relation
to population aggregates, sizes, and distributions, gene flow in respect to migra-
tion/exchange rates, the role of transfigured landscapes and attendant habitat distri-
bution, fragmentation, and uncongeniality under cyclic Pleistocene paleoclimatic
mechanisms, not to mention inexplicably high selection pressures in situations
strongly favorable to genetic drift. It has denied the role of speciation as a conse-
quence of populational isolation, fragmentation, or diminution, usually rejected
evidence of stasis in instances in which this effect is strongly indicated and hence of
evolutionary interest and significance, and dismissed the probability and potential
relevance of extinction events. Population dispersals, expansions, displacements, or
replacements are seemingly unenvisioned or disallowed. Although provincial and
regional evolutionary patterns and attendant processes are evidenced in hominin
evolution, a ‘hard’ MRE hypothesis obscures rather than enlightens serious investi-
gation into hominin phylogenesis.

The recent volumes of Howells (1993) and Tattersall (1993, 1995) reflect well
and more fully the perspective and positions on hominin evolution that I have sought
to adumbrate only briefly here.

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HOWELL

APPENDIX A

TABLES 1-3

CV
CVA
DF
D/M
D2
MC
MRA
PAUP
PC
P/s—sh
Rs
UPGMA

Key to Abbreviations of Table |

Canonical Variates Analysis

Canonical Variates Analysis, Q- or R-mode
Discriminate Function Analysis
Darroch/Mosiman Shape Discrimination
Mahalanobis Distance Statistic

Matrix Correlation

Multiple Regression Analysis

Phylogenetic Analysis Using Parsimony
Principal Components Analysis
Penrose-size/shape Statistic

Row Standardization Method

Unweighted Pair-Group Method with Arithmetic Mean

Group Integrity/A ffinity

African
European
Levantine
Asian
Sundaland
Modern-like

Nos. = Number of Specimens

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Paleoanthropology and
Preconception

lan Tattersall

Department of Anthropology
American Museum of Natural History
Central Park West at 79th Street

New York, NY 10024

Although discussion of the human fossil record began before an evolutionary
framework existed within which to understand it, certain canons of belief estab-
lished during this early period remain with us to this day. Principal among these
is a willingness to accept a maximum of morphological variety within Homo sapiens
while at the same time minimizing diversity among related fossil species. The
adoption of Darwinian concepts added to this unfortunate legacy the transforma-
tionist mindset which has since dominated paleoanthropology almost to the exclu-
sion of taxic diversification. This preoccupation is in turn related to a general denial
of the view of species as essentially stable entities, which has more recently
expressed itself in a widespread rejection of the notion of punctuated equilibria.
The resulting intellectual climate has encouraged the view that human phylogeny
is essentially a matter of discovery rather than a pattern of relationships among
taxa that requires analysis. In consequence much of hominin systematics has been
deprived of a coherent theoretical basis. It is critical that we develop a clear
appreciation of how mindset has influenced paleoanthropological belief, and that
we adopt more realistic criteria for species recognition in the human fossil record.

“If I have seen farther than other men,” said Isaac Newton, “it is because | have
stood on the shoulders of giants.” In these gracious words he acknowledged a debt
that is universal in science, no less in these days than in his own. Every branch of
modern science is the beneficiary not only of a great body of accumulated knowledge
but of a perspective on that knowledge that has been laboriously achieved over a great
period of time, and through the efforts of many gifted individuals. | hope that nothing
I say here will be taken as in any way belittling the contributions to our science of
our precursors in the field of paleoanthropology. I do want to point out, however, that
the precious legacy of the past also brings with it a burden that we could well do
without: not all received wisdom is truly worthy of that name. It is the task of every
generation of scientists to sort through its intellectual legacy, and in doing so to retain
and build upon what has stood the test of observation and repeated experience, while
discarding the rest. Despite this self-evident obligation, | fear that over the long haul

Contrmporary Issues in Human Evolution Memoir 21, Copyright © 1996
Editors, W.E. Meikle, F.C. Howell, & N.G. Jablonski California Academy of Sciences

48 TATTERSALL

paleoanthropologists have proven less ready than scientists in many other fields of
systematics to re-examine their assumptions.

We have paid a considerable price for this reluctance to question received wisdom.
It has caused us, for example, seriously to neglect or to underestimate the taxic
diversity that has arisen in the evolution of the human family (or, more strictly
speaking, of the tribe Hominini). The historical roots of this tendency are clear. When
the significance of the initial fossils of the first-known extinct human species, Homo
neanderthalensis, began to be disputed by anthropologists and human anatomists in
the late 1850s, there was no context other than that provided by living Homo sapiens
within which this remarkable new phenomenon was to be understood. All of the living
species of our closest (if quite distant) living relatives, the great apes, were known
by that time, and it was pretty evident to all concerned that the big-brained specimen
from the cave in the Neander Valley was no ape, even in the rather vague sense in
which that term was then understood. As the Neanderthal debate commenced, a
couple of years before the publication of The Origin of Species, there was no coherent
conception that we are linked to our nearest living relatives by a series of extinct
species that represent an evolutionary genealogy, a genealogy that does indeed tie us
in with the apes, with the monkeys, with the primates as a whole, and ultimately with
the entire diverse spectrum of living things.

It is hardly surprising, then, that the early European anthropologists and anato-
mists, who labored so hard to explain what the big-brained, beetle-browed, low- and
heavy-skulled Neanderthal specimen represented, sought to place this strange phe-
nomenon in the context of the world that they knew. Two principal possibilities
presented themselves. The first of these was that the Neanderthaler was somehow
pathological, the remains of a modern human victim of some obscure but morphol-
ogy-modifying disease. The second was that these remains had belonged to a member
of an extinct and primitive tribe, unrepresented in the modern world and thus
unknown to science in its living form (although such peoples had long been celebrated
in Western myths dating back to Classical times). Of all of the savants who com-
mented on the Neanderthal find, virtually only William King (1864) was prepared to
entertain the view that here was evidence of a separate, extinct species comparable
in some ways to the apes as well as to humans.

Eventually, scientists were forced to discount the first of these possibilities, that
of pathology, by repetitive discoveries of similar fossils in widely separated parts of
Europe. Pathology simply could not explain the consistency ofall of the accumulating
Neanderthal finds. But the second alternative remained, and remains with us still,
albeit in modified form. To this very day, the most egregious example of the ancient
tradition of cramming a bizarre array of forms into the species Homo sapiens is
provided by the allocation of the Neanderthals to the subspecies Homo sapiens
neanderthalensis. The routine parading out of the Neanderthals in textbooks of
physical anthropology as representatives of an extinct or reabsorbed subspecies of
our own species thus continues to infect the mindsets of successive generations of
physical anthropologists.

Perhaps ironically, this mindset was reinforced by the triumph of the evolutionary

PALEOANTHROPOLOGY AND PRECONCEPTION 49

synthesis of the 1930s and 1940s (e.g., Dobzhansky 1937; Mayr 1942; Simpson 1944)
which among other things emphasized the importance of variation within species.
For systematists accustomed to dealing with the variety of species in the living world
(most of which possess much closer extant relatives than we do) this has been a
salutary development, combating the ancient and perfidious typological tendency of
one specimen, one name. But to anatomists and anthropologists, whose training and
experience were traditionally limited to the documentation of variation within the
one species Homo sapiens (with perhaps an occasional glance at the other hominoid
genera, all notably unspeciose), it has proven dangerous indeed. It simply reinforced
an already deeply entrenched viewpoint that was prepared to accept maximum variety
within the one living species around which the sciences of human anatomy and
anthropology revolve, while recognizing minimum variety at the species level and
above in the fossil record of human precursors.

This viewpoint is still very much with us today and represents the aspect of
received wisdom in paleoanthropology that cries out, above all else, for re-evaluation.
Species provide the essential basis for all systematic analysis, whether of humans or
of any other group. Yet our ideas of species in paleoanthropology still tend to be
dominated by Charles Darwin’s brilliant response to a specific set of beliefs that
dominated Victorian society a century and a half ago. Darwin’s idea, that species
gradually transform themselves out of existence over vast stretches of time, was born
of an essentially political need to combat the Biblically-grounded view of species as
immutable. The proposition that gradual natural selection is the agent of such change
gave this proposal a powerful appeal. Its attractiveness was further strengthened by
the addition of a genetic basis when the architects of the “New Synthesis” argued that
virtually all evolutionary phenomena could be reduced to the influence of natural
selection working on the gene pools of populations over vast periods of time.

It has to be pointed out, however, that this putatively all-embracing mechanism
ignores the contingent effects of climate and geography. These crucial forces are
largely random with respect to adaptation, and they are also decidedly irregular with
respect to time. What’s more, the gradualist mechanism also disregards the little that
we know about speciation in mammal populations and has distorted our interpreta-
tions of the fossil record. It does, though, have the advantage of a magnificent
simplicity and of the intellectual appeal that simplicity always exerts on the human
mind, a mechanism that seems to crave elegant explanation. The world may in fact
be a rather complicated, unfathomable place; concordantly complex explanations,
however, seem to be singularly unattractive to our ratiocinative faculties.

For better or for worse, though, if we wish to discover pattern in the fossil record
we need to have a realistic working conception of what we mean by species. I use
the modifier (“working” conception) here for two reasons. First of all, we know that
speciation (in the sense of the splitting of lineages rather than their gradual transfor-
mation) must occur, for otherwise life could never have diversified. However, we
know little about the mechanisms that underlie this fundamental process. Indeed, it
seems likely that speciation is not in fact a genetic event of a specific kind, but that
it results instead from genetic disruptions of a particular class, underlain by a variety

50 TATTERSALL

of mechanisms (Godfrey & Marks 1991; Tattersall 1992). | have summarized
elsewhere (Tattersall 1992) some of the problems that are posed by the various major
species concepts currently on offer. Suffice it to note here that as long as we do not
fully understand what speciation is, we will find it hard to be definitive about what
species are.

On the other hand, it is already clear what species are not: they are not simply the
passive results of accumulating adaptive change (Tattersall 1991). This is dramati-
cally underlined by the recent study of Sturmbauer & Meyer (1992), who found
genetic, morphological, and taxic divergence to be effectively unrelated among
species of cichlid fishes living in various lakes of the East African Rift system. The
obvious problem for paleontologists is that, if there is no close correlation between
speciation, time, and any specifiable degree of morphological change in the skeleton
and dentition (the only body systems for which information on extinct forms 1s
routinely available), there can be, for the time being at least, no objective means of
recognizing species in the fossil record. There exists, of course, a vague association
between morphology and speciation in the sense that speciation has to intervene in
the context of a geographically differentiating population, but there 1s no direct link
between the two.

I have suggested elsewhere (Tattersall 1986, 1991, 1992) that this should not be
a major problem in practical terms if we are prepared to realize that species in general
represent a rather low level of morphological differentiation. So low, indeed, that
where distinct skeletodental morphs can be recognized we are on pretty firm ground
in recognizing entities which are at the very least species in a genetic sense. Indeed,
such morphs are perhaps just as likely to represent monophyletic groups of closely
related species as they are to represent individual species. When compared to
conventional interpretations of the human fossil record (at most a mere five species
between Australopithecus afarensis and Homo sapiens), this observation suggests
that paleoanthropologists have traditionally been prone to overestimate how much
morphological variety is likely to accumulate within a species before it becomes
extinct or splits into two or more daughter species. In part this tendency has resulted
from the historical circumstances already adumbrated, but it has clearly been rein-
forced by another related factor as well. Several years ago Eldredge (1979) pointed
out that the evolutionary process possesses two aspects: morphological transforma-
tion and taxic diversification. To transformationists, evolution centers around accu-
mulating changes in genes and their products, and the role of the paleontologist is to
track such change through time. The focus is thus upon aspects of morphology and
the potential agents of selection bearing upon them. How morphology is packaged
into species is very much a subsidiary concern, if indeed it is a concer at all.

The tradition in paleoanthropology has thus overwhelmingly been one of trans-
formationism. The result has been that in our science the second major aspect of
evolution, the splitting of species and hence the origin of taxic diversity, has tended
to be relegated to a secondary role, to be ignored, or even to be totally denied. In
witness to this one has only to think of the single-species hypothesis that enjoyed
such a vogue in the 1960s and early 1970s (e.g., Wolpoff 1973) or of its precursor

PALEOANTHROPOLOGY AND PRECONCEPTION 51

and latter-day descendant, the movement to sink Homo erectus as well as all
subsequent hominins into the species Homo sapiens (e.g., Thoma 1970; Wolpoff
1992). This transformationist tradition is closely linked, of course, with the pervasive
notion in paleoanthropology that the unraveling of human evolutionary history is
effectively a matter of discovery (Eldredge & Tattersall 1975): if we crawl over
enough outcrops and discover enough fossils, all will eventually be revealed unto us.
“We need more fossils” is an obligate part of the paleoanthropological litany, while
the lament that “we need better methods of phylogenetic analysis” is far more rarely
found in the concluding sections of papers on the human fossil record.

Perhaps I may be permitted a personal reminiscence here. As a graduate student
I watched fascinated as visiting researchers diligently made reams of notes on fossils
in the collections room where I had my desk. I had a hard time figuring out what they
were actually doing, even though I was presumably there to learn to emulate them.
Eventually I plucked up the courage to ask a distinguished paleoanthropologist to
reveal the secret of how to study fossils. He thought for a moment, then said: “Well,
you look at them for long enough, and they speak to you.” Of course, I have since
come to learn that there is actually a great deal more wisdom in that answer than I
realized at the time, but it does illustrate very neatly how, right up through the 1960s,
the practice of paleoanthropology, like that of vertebrate paleontology in general, was
very much an intuitive affair. The reconstruction of phylogeny was bereft of any
rigorous theoretical framework and in general did not yield hypotheses that were
objectively comparable one with another. The field was discovery-driven. Admit-
tedly, this had brought paleontology a remarkably long way, but it is no wonder that
I was delighted to make my own discovery of cladism after arriving at the American
Museum of Natural History.

My pleasure at discovering this theoretically coherent, practical approach to the
analysis of relationships among fossil and living species has not, however, been as
widely shared as it might have by my colleagues in paleoanthropology. Despite the
practical difficulties that cladism undoubtedly does present in such areas as the
definition of characters and the determination of morphocline polarities, it is, | think,
principally as a result of the long-standing transformationist bias in paleoanthropol-
ogy that the cladistic approach to the reconstruction of phylogeny has made so little
impression upon the field. The fact that much of the vocabulary of cladism has been
co-opted into paleoanthropological jargon should not be mistaken for wholesale
adoption of its principles. While it is probably true by now that most vertebrate
paleontologists outside the primate field have come to recognize the value of
proceeding from simple hypotheses of sister relationships to more complex hypothe-
ses of ancestry and descent, and only finally adding to the brew such ingredients as
ecology and adaptation (Tattersall & Eldredge 1977), paleoanthropological hypothe-
ses still tend to be introduced at the level of the scenario (a complex mishmash of
relationships, time, adaptation, and ecology) rather than at the simpler levels at which
hypotheses are actually (or at least potentially) testable. It is also because of the weight
of transformational traditionalism that many paleoanthropologists have been so ready
to reject notions of punctuated equilibrium as opposed to phyletic gradualism in

AN
ine)

TATTERSALL

evolution. Such out-of-hand rejection has been easier to accomplish in paleoanthro-
pology than in most branches of vertebrate paleontology. This is for the simple reason
that we are dealing in our field with a single extremely closely related group of
organisms. Within such close-knit groups, “intermediates” between members —
traditionally accepted as prima facie evidence of continuity — are particularly easy
to find.

This 1s so for two reasons, having to do both with homology and homoplasy (the
independent acquisition of evolutionary novelties in two or more species). The more
closely two species (or populations) are related, the more alike they will almost
certainly be genetically. They are likely to overlap substantially or totally in the
ranges of variation of almost all of their morphological characters. Further, the more
similar such populations are genetically, the more likely it becomes that the same
genetic innovations will arise independently within each. The practical problems that
these likelihoods raise for the working paleontologist become yet more acute when
we factor in the consideration that closely related species will not only share the same
major constellation of adaptive characters, but that they will generally experience at
least broadly equivalent ecological pressures. Natural selection takes place at the
level of the local population, and in similar circumstances closely related populations
are likely to respond to ecological pressures or other agents of natural selection upon
them in similar ways. These various considerations will hold true even when such
local populations have become individual evolutionary entities. When, that is,
speciation (which takes place for reasons that are not necessarily or even at all related
to adaptation) has intervened between them.

This is a problem that has received remarkably little attention from paleoanthro-
pologists. For all the interminable measuring that has been done, as far as | am aware
few people have troubled to investigate the patterns of distribution of skeletodental
characteristics between defined populations of living primates at the specific and
intraspecific levels. When Schwartz and I (Schwartz & Tattersall 1991) tried this
recently on a group of extant lemur species, using the quantitative parsimony
procedure PAUP on what we had thought was a very substantial character set, we
came up with 80 alternative trees of equal probability. This indeterminate result was
evidently caused by extensive homoplasy (as might have been expected, for the
reasons already given). It further resulted in the conclusion (Tattersall 1993) that the
number of taxa in our sample, at both the specific and the infraspecific levels, would
have been seriously underestimated by a paleontologist using our data set to sort out
the alpha taxonomy of this closely related group in ignorance of the “biological”
information (behavioral, distributional, external morphological, karyotypic) which
we had possessed at the outset of our study.

We have no reason to believe that the group we chose for our study 1s in any way
atypical for primates in general, and our experience dramatically illustrates the
difficulties that lie in wait for systematists, such as paleoanthropologists interested
in the genus Homo or even in the tribe Hominini, who are concerned with taxa that
are differentiated at a very low level. The empirically demonstrated as well as
theoretically expected tendency towards high levels of homoplasy among closely

PALEOANTHROPOLOGY AND PRECONCEPTION 53

related species points towards a built-in likelihood that we will underestimate the
abundance of species in the human fossil record, and it also suggests that we should
not be surprised to encounter supposedly “Neanderthal-like” characters in early
Homo sapiens from Europe. Such characters, particularly in the supraorbital and
occipital regions, were cited in earlier years in support of a Neanderthal ancestry for
modern humans in that part of the world, and more latterly have been adduced as
evidence for some admixture between the two.

To return to matters of mindset, what you expect of the evolutionary process
clearly affects what you will see in the fossil record. The ongoing debate between
proponents of the “multiregional” and “center of origin” models of the emergence of
Homo sapiens reflects theoretical expectations at least as much as it does the facts of
the fossil record. Those who, in the spirit of the “New Synthesis,” see human
evolution as a long trudge from benightedness to enlightenment will grasp at the
“evidence” for continuity furnished by the expectable homoplasy between closely
related hominin species. Those who, on the other hand, prefer to acknowledge the
largely contingent nature of the real world will look for centers of origin. For little as
we know about the process, or processes, of speciation among primates, we do know
that it, or they, do require the physical division of a pre-existing species and the
interruption of free-flowing genetic contact between its components. The isolation
of infraspecific populations is thus a prerequisite for speciation, and the occasions
for such isolation can rarely have occurred more frequently than during the dramatic
climatic and glacio-eustatic fluctuations of the Pleistocene, the epoch which saw the
appearance of most of the innovations documented in the human fossil and archeo-
logical records.

My purpose here, however, is not to espouse any specific views of how human
evolution proceeded at any particular point in time. That will be done much more
competently than I can by the other contributors to this symposium. I want, rather, to
emphasize that at its fundamental systematic level our study of human evolution 1s
in essence a search for historical pattern, and that it is thus a matter of analysis as
much as it is of discovery. Fossils are essential, but they don’t speak. Particularly at
the low levels of morphological differentiation involved in paleoanthropology, the
patterns we perceive are as likely to result from our unconscious mindsets as from
the evidence itself. This, above all, is why I believe that it is our responsibility to our
illustrious predecessors, as much as it is to ourselves, to re-examine our received
attitudes from time to time, to ensure that we are building on the foundations of the
past, rather than staying entombed in their ruins.

Acknowledgements

For the opportunity to make these remarks I should like to acknowledge my
gratitude to the Paul L. and Phyllis Wattis Foundation Endowment and to the
California Academy of Sciences. Appreciation for the organization of an exception-
ally stimulating symposium is also due to Roy Eisenhardt, the Academy’s Executive

54 TATTERSALL

Director Emeritus, to Linda S. Cordell, former Irvine Curator of Anthropology, and
above all to Deborah W. Stratmann, the Symposium Coordinator.

Literature Cited

Dobzhansky, T. 1937. Genetics and the Origin of Species. Columbia University Press, New
York. 364 pp.

Eldredge, N. 1979. Alternative approaches to evolutionary theory. Bull. Carnegie Mus. Nat.
Hist. 13:7-19.

_& I. Tattersall. 1975. Evolutionary models, phylogenetic reconstruction, and another
look at hominid phylogeny. Pages 218-243 in F. S. Szalay, ed., Contributions to Primatol-
ogy, Vol. 5: Approaches to Primate Paleobiology. Karger, Basel, Switzerland.

Godfrey, L. R., & J. Marks. 1991. The nature and origins of primate species. Yearb. Phys
Anthropol. 34:39-68.

King, W. 1864. The reputed fossil man of the Neanderthal. Quart. Jour. Sci. 1:88-97.

Mayr, E. 1942. Systematics and the Origin of Species. Columbia University Press, New York.
334 pp.

Schwartz, J. H., & I. Tattersall. 1991. Phylogeny and nomenclature in the Lemur-group of
Malagasy strepsirhine primates. Anthropol. Pap. American Mus. Nat. Hist. 69:1-18.

Simpson, G. G. 1944, Tempo and Mode in Evolution. Columbia University Press, New York.
237 pp.

Sturmbauer, C., & A. Meyer. 1992. Genetic divergence, speciation and morphological stasis
in a lineage of African cichlid fishes. Natwre 358:578-581.

Tattersall, 1. 1986. Species recognition in human paleontology. Jour. Hum. Evol. 15:165-175,

_ 1991. What was the human revolution? Jour. Hum. Evol. 20:77-83.

1992. Species concepts and species identification in human evolution. Jour. Hum
Evol, 22:341-349.

1993. Speciation and morphological differentiation in the genus Lemur. Pages
163-176 in W. H. Kimbel & L. B. Martin, eds., Species, Species Concepts, and Primate
Evolution. Plenum Press, New York.

,& N. Eldredge. 1977. Fact, theory and fantasy in human evolution. American Sci.
65:204-211.

Thoma, A. 1970. Selektion, Gendiffusion und Spezialitétméglichkeiten bei den Hominiden.
Homo 21:54-60.

Wolpoff, M. H. 1973. The single species hypothesis and early hominid evolution. Pages 5-15
in D. Lathrap & A. Douglas, eds., Variation in Anthropology. Mlinois Archaeological
Survey, Carbondale, Illinois.

. 1992. Homo erectus in Europe: An issue of grade, of clade, or perhaps no issue at all.
Jour. Israel Prehist. Soc., Suppl. 1:137.

nN
n

Grades and Clades:
A Paleontological Perspective
on Phylogenetic Issues

Pascal Tassy

Laboratoire de Paléontologie des Vertébreés et Paleéontologie Humaine,
Université-Pierre-et-Marie Curie

4, place Jussieu

75252 Paris Cedex 05, France

The dualistic nature of fossils is responsible for the historical and current
debates on the relations between paleontology, evolution, and phylogeny recon-
struction. Because they ally shape (morphology) and stratigraphy (time), fossils
have been considered either as evolutionary or phylogenetic facts. Though fossils,
as objects, are geological facts, their interrelations — as either lineages or sister
groups — are hypotheses. There is no proper paleontological approach to phylo-
geny. Time does not give polarity or relationships; only interpretation of morphol-
ogy does. This interpretation depends on methodological choices, either phenetic
or cladistic. Some aspects of debates from Lamarck to the present are historically
reviewed.

Twenty years ago a paper on the relations between paleontology and phylogeny
reconstruction was published (Schaeffer e¢ a/. 1972). This paper can be considered a
landmark in the paleontological literature. Paleontologists acknowledged the hetero-
dox view defended by some neontologists (Hennig 1950) that paleontology was not
the major discipline in phylogenetic research. Briefly, the message was, “time per se
cannot be employed in hypothesizing relationships” (Schaeffer e¢ al. 1972:34).
Cladistics was favored as a phylogenetic methodology whose premises were devoid
of ambiguity. A consequence of cladistic inquiries was that sister-group relationships
form the core of phylogenetic construction, not direct ancestor-descendant relation-
ships.

One can argue today that little can be added, though debates have flourished since
1972. I would say roughly that, like the phoenix, the same arguments have been
opposed again and again, year after year, in more or less sophisticated manners,
because of key disagreements over basic concepts: What is phylogeny? What is
phylogenetic information? What is the nature of paleontological information? After

Contemporary Issues in Human Evolution Memorr 21, Copyright © 1996
Editors, W.E. Meikle, F.C. Howell, & N. G. Jablonski California Academy of Sciences

56 TASSY

1972, paleontologists, as a whole, did not promptly change their habits. Schaeffer e¢
al. (1972:43) anticipated that “the purposeful omission of biostratigraphic informa-
tion will meet with disfavor on the part of many paleontologists.” Nevertheless,
cladistic approaches became more frequent in the paleontological literature, espe-
cially during the last decade. Consequently, present discussions focus on the relations
between cladistic analyses and the fossil record (e.g., Norell & Novacek 1992;
Novacek 1992b), which is undoubtedly a sign of change.

The thesis of this paper is that there is no specific paleontological approach to
phylogenetic issues. On the contrary, one can observe different general approaches
to phylogeny and to phylogenetic concepts, approaches that are all based on more
philosophical attitudes toward the meaning of phylogeny reconstruction. These
approaches influence or direct paleontological statements, that is the way we use
paleontological data to infer phylogeny (Tassy 1981). Data are subordinate to the
approaches. Naturally, this thesis has no implications for the question of the respec-
tive merits of data taken from extinct and extant taxa and does not imply that
paleontological data are unnecessary to phylogenetic reconstruction. Fossils are
crucial for a better understanding of relationships first based on extant taxa only (e.g.,
Gauthier ef al. 1988).

This thesis is hardly new. The relationship of fossils to the phenonenon of
evolution already heated debates during the early 19th century. The various concep-
tions of the evolutionary process, and the triumph of gradualism later in the 19th
century, heavily influenced paleontological studies in the 20th century. The distinc-
tion between pattern and process in evolutionary studies, emphasized in the cladistic
literature of the 1970s, renewed not only empirical phylogenetic studies, but also old
debates on the nature of phylogeny and of phylogenetic entities.

In the rapid review proposed here I will try to show, following Rudwick (1976),
that the ambiguous — dualistic — nature of fossils (shape and time) is one Ariadne’s
clue for understanding the persistence of debates from Lamarck’s day to the present.

Fossils and the Dawn of Evolutionary Thinking

I will recall briefly the two ways in which fossils were considered relative to the
concept of evolution in the 19th century.

Cuvier — popularly presented as the founder of paleontology — used fossil ver-
tebrates to demonstrate that evolution did not occur. The different past faunas
described by him were interpreted as evidence of catastrophism with successive
creations (Cuvier 1825). When Cuvier (1796) described his “Animal du Paraguay”
(Megatherium), he assumed anatomical similarities between the fossil species and
the extant two-toed tree sloth (Choloepus) and three-toed tree sloth (Bradypus), but
— rightly — assumed no ancestor-descendant relationships between the fossil and
the living taxa. Had Cuvier thought of common ancestry and not of direct ancestor-
descendant relationships, the history of evolutionary research would have been quite
different. But, indeed, it was then common sense to think of evolution as a synonym
of direct ancestor-descendant relations.

PALEONTOLOGY AND PHYLOGENY Sy

On the contrary, Lamarck, popularly presented as the founder of the earliest
rationalized theory of evolution, used fossils to demonstrate that species evolve
during geologic time, so that fossil species can be linked to extant ones. There is a
controversy on the role of fossils in the emergence of Lamarck’s evolutionary
thinking (compare Burckhardt 1977 and Laurent 1987). Although fossils play nearly
no role in Lamarck’s Philosophie zoologique (1809), fossil invertebrates studied by
Lamarck himself were crucial to the emergence of the concept of transition through
time from fossil species to extant ones, a decidedly evolutionary concept. In his
Mémoires sur les fossiles des environs de Paris, published between 1802 and 1808,
Lamarck described in detail the morphological variation of fossil shells in the
stratigraphic context and included in the same taxonomy extant and extinct molluscs.
For Cuvier & Brongniart (1811), the succession of post-Cretaceous faunas in the Paris
Basin proved the interruptions of life. The study of the same period and area brought
Lamarck to the opposite conclusion. One can think that it must have been easier to
follow continuity through time on shells rather than on skeletons. However, if
vertebrates are considered, one can recall the conclusions drawn by Geoffroy Saint-
Hilaire (1831:74) from the study of fossil crocodiles from Normandie, western part
of Paris Basin, and the opposite of those of Cuvier: the animals living today arose
from the animals of the antediluvian world.

The different conclusions drawn by these historical figures were based on their
global conception of life, probably fed, as usual, by intuition, empirical observations,
and various metaphysical concerns. For example, Geoffroy Saint-Hilaire was guided
by his grand view of the unity of composition, the “unite de plan,” and he proposed
a program for studies of fossil and recent organisms that fit with this unity: what was
to be shown was how living species, by means ofa kind of filiation, could be extended
back to the earliest inhabitants of the earth, knowledge of which could be gained from
their fragments in the fossil condition (Geoffroy Saint-Hilaire 1806:222).

Phylogeny, Grades, and Clades

Apart from the question of the role of paleontological data, the concept of
phylogeny itself is an everlasting source of conflicts. The word “phylogeny” was
coined by Haeckel (1866:57), originally as “the history of the development of groups
(phyla),” development being understood in the modern sense of evolution. Sub-
sequently, Haeckel (1874:18) mentioned that this “history” appeared in the dimen-
sion of geological time when he defined phylogeny as the “history of paleontological
development of organic beings,” as opposed to the history of individual development
(ontogeny). Here “paleontological” does not imply that only fossil taxa are involved:
all phylogenetic trees drawn by Haeckel include extinct and extant taxa. In the sixth
edition of the Origin of Species, Darwin (1872:381) introduced the word “phylogeny”
with the following definition: “the lines of descent of all organic beings.”

I see “history” as the key word of the original definition, and ] would define the
concept as the history of descent of the organic beings. Yet, discussions over the
decades have their origin in the double aspect of phylogeny: the pattern of branching

58 TASSY

and the amount of difference displayed by the branches. Darwin clearly contrasted
the two, and, correlatively, the double nature of similarity. “The arrangement of the
groups... in due subordination and relation to each other, must be strictly genealogi-
cal in order to be natural; but . . . the amount of difference in the several branches or
groups, though allied in the same degree in blood to their progenitor, may differ
greatly, being due to the different degrees of modification which they have under-
gone” (Darwin 1859:420). Hence we must differently rely on “strongly-marked
differences in some few points, that is the amount of modification undergone” and
“unimportant points, as indicating the lines of descent” (Darwin 1871:195). The well-
known, single figure in the Origin of Species is a model: a tree in the geological
dimension which exemplifies the branching aspect, that is the origin of species by
splitting. Darwin contrasted “common descent” (the “arrangement” or lines of
descent), and the “amount of difference” or degree of divergence. This amount does
not alter the arrangement: “the amount of value of the differences between organic
beings all related to each other in the same degree in blood, has come to be widely
different. Nevertheless their genealogical arrangement remains strictly true, not only
at the present time, but at each successive period of descent” (Darwin 1859:421).

Conflicts on the meaning of phylogeny, as well as the concepts of grade (=
evolutionary levels) and clade (= monophyletic units), formalized by J. Huxley
(1957), take their root in the two aspects of phylogeny detailed by Darwin. Recently,
Mayr (1985:97-98) defined phylogeny as “the splitting of phyletic lineages as well
as the amount by which they subsequently diverged,” cladistics being the “branching
of phyletic lineage,” or “genealogy” (Mayr 1985:98). This semantic discussion is
secondary to the question of the elucidation of relationships among organisms;
nevertheless it exemplifies the weight of the two concepts.

We can read in Darwin’s quotations that divergence is subordinated to the pattern
of relationships. We read how the study of branching — the concept of clade — and
the study of divergence — the concept of grade — will yield different evolutionary
constructions with disputed relations to the concept of phylogeny.

Moreover, Darwinian and neo-Darwinian students undoubtedly favored one as-
pect of the evolutionary process — gradualism. Although we must bear in mind the
fact that Darwin (1859:118; 1872:279, 312-313) acknowledged the possibility of
periods of rapid evolution, gradualism was held as the dominant mode of evolution
(Eldredge and Gould 1972, 1986). Consequently it was used as a model for most
paleontological and neontological studies. Darwinism conceived evolution as adap-
tation through natural selection, the evolutionary process being largely gradual. One
major consequence of Darwinism viewed as a research programme was the search
for “laws of evolution” (T. H. Huxley 1880). Adaptation explains that the same
evolutionary level (Julian Huxley’s grade) can be reached independently by different
groups or lineages. Hence a group, or a lineage seen as a series of ancestors and
descendants, go through different evolutionary levels, or grades.

At the smallest taxonomic level a grade can be defined as a “mutation,” a word
introduced by the German paleontologist W. Waagen (1867) as the smallest trans-
formation that can be reckoned in a phyletic lineage. At a higher level, we can see T.

PALEONTOLOGY AND PHYLOGENY 59

H. Huxley’s “laws of evolution” as a prefiguration of the grade concept, together with
the emphasis of the phenomenon of convergence. In his famous diagram (Figure 1),
the different orders of mammals are shown to reach independently different evolu-
tionary stages, that is different grades. Lineages, grades, and evolutionary conver-
gence, once associated in one picture, summarize the laws of evolution. Common
descent then appeared to be unnecessary to explain evolution.

If paleontology has to prove evolution using fossils to show gradual change
through time, we can easily conclude that the concepts of lineages and grades are
adequate to fufill this program. Following Waagen, the French paleontologist Deperet
used the concepts of lineage and mutation to demonstrate evolution in a strictly
positivist attitude. Fossils were “facts”: real organisms frozen in the rocks. A lineage
— in Deperet’s (1907:197) words a “rameau phyletique” — is the vertical line made
from a series of fossils closely related by means of direct descent. Hence, not only
were fossils facts, lineages were too. According to Deperet (1907:172), “mutations,
slow and gradual” occurred in these lineages, which can be “traced back from layer
to layer through the series of sedimentary stages.” For Deperet a lineage is not a
hypothesis or construction, and paleontology is able to identify what he calls “the
real phylogenetic series.” Depéret’s diagram depicting the evolution of probos-
cideans (Figure 2) is very reminiscent of Huxley’s illustration of the evolution of
recent mammals. Once again, common descent does not appear to be necessary to
illustrate the “fact” of evolution. The recognition in Figure 2 of the lineage “molaires
a mamelons coniques” precludes any hypothesis of close relationships between
tetralophodont gomphotheres (here “M/. /ongirostris” and “M. arverensis”) and
elephants. As we know today, this lineage “molaires a mamelons coniques” is not a
totality of descent. We can recognize without difficulty in Depeéret’s diagram phyletic
gradualism and the basic concepts of biostratigraphy. Direct ancestor-descendant
relations between fossil species was the key concept. The positivist attitude can be
compared to “common sense”: without ancestors, no evolution. Hence, if evolution
is real, evolutionary studies are the search among fossils for real ancestors. The basis
of this program was that stratigraphy enables us to see the course of evolution, or in
modern words, the polarity of transformations. This is the “piege du bon sens” as
Dupuis said (1986:233) or, even more roughly, “superstition” (Nelson & Platnick
1981:333). For more comments on Depéret’s ideas on phylogeny see Tassy (1991).

A consequence of the emphasis on gradualism in the neo-Darwinian program 1s
that paleontological data have been largely used as tools for illustrating phyletic
gradualism or anagenesis. Stratophenetics (Gingerich 1979) reconciles two processes
of evolution: cladogenesis (splitting; that is, production of taxic diversity) and
anagenesis, two terms defined by Rensch (1954). Anagenesis was originally con-
ceived for higher taxa, not only for species: the acquisition of higher levels by
progressive evolution. Today, anagenesis is often understood as phyletic gradualism:
transformation at the species level without production of taxic diversity. Neverthe-
less, stratophenetics treats fossils in the same way Depéret did: time — that is,
stratigraphical position — is the key by which to interpret phenetic similarity and
thus to hypothesize transformation for elucidating relationships.

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62 TASSY

It can hardly be denied that the search for grades has been one of the major
activities of neo-Darwinian paleontology, up to the 1980s. The evolutionary nature
of the grade concept can also hardly be denied. However, it is certainly not a
phylogenetic concept since it makes no reference to genealogical relationships.
Huxley (1957) expressively contrasted the evolutionary concept of grade and the
phylogenetic concept of clade. A clade (*branch” in Greek) is a monophyletic group,
a totality of descent. For historical interest, it can be noted that, earlier, Cuenot (1940)
coined the word “clade” with a somehow different meaning: an autonomous leaf of
the tree corresponding to a defined structural type, that is, a Bauplan or fundamental
body plan. I would call this a grade, notwithstanding the adjective “autonomous”
which suggests, in some way, monophyly.

If clades, contrary to grades, are phylogenetic concepts, phylogenetic inquiries
should focus on clades, on monophyletic groups. And here we are: the emergence of
cladistics and, again, the ambiguous role of paleontology in phylogenetic studies.

Clades and Paleontology

Schaeffer ef a/. (1972) showed that paleontological data and cladistic analysis are
not in conflict, although the use of the paleontological argument for polarizing
characters could be misleading: chronoclines are not necessarily identical to morpho-
clines.

The respective roles of the different criteria for polarizing character transforma-
tions are the cause of numerous debates. The priority of outgroup comparison (Wiley
1976) or ontogenetic argument (Nelson 1973) is particularly discussed between
so-called phylogenetic cladists and pattern cladists (e.g., Kluge 1985; Nelson 1985).
Hennig (1966) emphasized that paleontology was not per se the phylogenetic method.
Nevertheless, the paleontologic argument — also called geological precedence, now
acknowledged to be an auxiliary argument — was presented as the first criterion by
proponents of cladistic procedures, such as Hennig (1966) himself (but not Hennig
1950) or critics such as Mayr (1986).

Hennig (1966:95) presented the paleontologic argument in the following words:
if in amonophyletic group a particular character condition occurs only in older fossils,
then obviously this is the plesiomorphous, and anything occuring later is the apomor-
phous, condition of a morphocline. This has been widely illustrated, and indeed,
occurs in a vast number of cases. However, it cannot be used as a primary rule as
recognized by Schaeffer et al. (1972). Even if it is accepted and used in priority,
Hennig’s definition leaves us with an unresolved question: how to identify the
monophyly of the considered group? Certainly not with the criterion of geological
precedence, or any morphological character seen in any Devonian taxon would be
more primitive than any trait seen in any Carboniferous taxon; diversification is an
old affair. This crude example explains why time does not yield relationship. The risk
of circularity in the paleontological reasoning (ancient = primitive) has been pointed
out many times (e.g., Cracraft 1981) and acknowledged by some paleontologists (e.g.,
Schaeffer et a/. 1972; Goujet et al. 1983; Janvier 1984).

PALEONTOLOGY AND PHYLOGENY 63

A clade is a set comprising subsets that are subclades, and the considered clade 1s
itself a subset of a more comprehensive clade. This statement applies to clades of any
rank and, if populations are accepted to be the unit of evolution, it involves species
as well. As Nelson (1989:287) concludes: a species is only a taxon. The pattern of
taxic diversity explains why the criterion of geological precedence is at best an
auxiliary criterion. If character analysis of intrinsic characters of organisms 1s
considered, comparative anatomy — or in more modern words: outgroup compari-
sons — cannot be ignored.

Figures 3-6 summarize the problems related to the paleontological criterion. Three
(Fig. 3) or one (Fig. 4) morphoclines are assumed in species A-D. Lineages (Fig. 3A,
4A) are compatible with cladograms (Fig. 3B, 4B). Both represent the same distri-
bution of characters. The number of branches strikingly differ. Lineages are “closed
systems”: the total information is assumed to be known; ancestors and descendants
are identified. Cladograms are “open systems.” They imply the existence of unknown
populations that could ultimately be discovered and introduced in the cladogram
without changing it. Species D could share a common ancestor with species C,
situated in a place different from the basin where species A, B, C, and D, were
previously found. Figure 5 shows an extreme example. Here, gaps hide the transfor-
mation series. The chronocline is the reversed morphocline. This kind of situation
can be recognized if other fossils are considered which are related to the species under
study and which bear some characters found in (A, B, C, D), such as a”. This is the
outgroup criterion.

The situations displayed by Figures 3-4 and Figure 5 can be mixed. In this case,
chronoclines will partly fail to find the solution reached by morphocline analysis
through the outgroup criterion. Figure 6 shows such a case. The transformation series
a-a’ and b-b’ (Figure 6A) cannot be found by chronocline analysis. If state a’ of taxon
A (chronological stage |) is hypothesized to be ancestral for state a of taxon B, C,
and D (chronological stages 2, 3, and 4), the chronocline a’-a gives the wrong solution
(Figure 6B). If state b’ of taxon B (chronological stage 2) is hypothesized to be
ancestral for state b of taxon C (chronological stage 3), the series b—b’—»b implies
homoplasy (reversal), which is the wrong solution (Figure 6B). If one admits that the
fossil record is fair, and assume that the stratigraphical occurrence of taxa A, B, C,
and D, reflects ancestor-descendant relationships, the taxic diversity is minimized:
only one branch is recognized. In the case of Figure 6 this will be wrong, and the
polarity of series a’—a, and b-b’—b will be wrong. The lineage (Figure 6B) will be
less parsimonious (6 steps), while two splits imply 5 steps (Figure 6A). The criterion
of geological precedence applied in priority, independantly of any other citerion,
cannot identify the phylogeny displayed by Figure 6A. This example is not unrealis-
tic, as will seen further on.

The cases illustrated by Figures 3-6 involve species. Taxonomically speaking,
these species are terminal taxa that cannot be hierarchically subdivided on the basis
of character analysis. If not, a terminal taxon is a set of subtaxa, and a lineage of such
taxa means nothing else than a sequence of paraphyletic higher taxa, that is meta-

64 TASSY

time

C c | /
° al Lf
th” SRE

FIGURE 3. The criterion of geologic precedence. A-D: species; 1-4: geological stages; aa’,
bb’, cc’: morphoclines identical to chronoclines.

time

a” D
a | Cc
a’ | B
ca)

FIGURE 4. The criterion of geologic precedence. Abbreviations: see Figure 3.
a—a'’—>a"—> a": morphocline identical to chronocline.

phorical ancestors. The criterion of geological precedence applies without ambiguity
only in the case of phyletic lineages, but the prerequisite of accepting one phyletic
lineage is that the fossil record is complete. If not, we are left with the possibility that
diversity occurred, and accept as a competitive hypothesis a phylogenetic tree
identical to the cladogram. On the basis of characters only, a phylogenetic lineage
cannot be proved to be more probable than the corresponding tree. Extrinsic data are
necessary, the applicability of which is conditioned by the minimization of taxic
diversity: given a paleontological set, the fossil record is accepted to be complete.

PALEONTOLOGY AND PHYLOGENY 65

Only in that case would ances-
tor-descendant relationships
between two taxa (one lineage)
be preferred to sister-group re-
lationships between two taxa
(two lineages).

There is a methodological
necessity in minimizing evolu-
tionary events, or steps. Other-
wise any shared-derived state
in various taxa could have oc-
curred more than once, inde-
pendently in each taxon. In that
case common descent does not
occur.

The procedure of phylo-
geny inference can be labelled
a two-stage procedure: first,
hypothesis of synapomorphy
(minimization); second, construction of a pattern of taxa. | see this minimization as
the inevitable sequel of the theory of descent. Certainly the procedure of minimization
of evolutionary steps has consequences on the second stage (taxa and their relation-
ships), but it does not apply directly at this stage. On the contrary, there is no
methodological necessity for minimizing taxic diversity. Such a minimization would
first affect the results (taxa) —that is, the second stage of the procedure — an

time

FIGURE 5. Refutation of the criterion of geologic
precedence. Abbreviations: see Figure 3. Morphocline:
a’ a"—a'—a; Chronocline: a>a’—>a"—>al”’

FIGURE 6. Refutation of the criterion of geologic precedence and mosaic evolution in the
history of three transformation series. A: branching phylogeny; B: lineage based on chronocline

analysis. Morphoclines: aa’, bb’, c—c’>c"—>c"’. Chronoclines: a’a, b>b’—>b,
c>c’>c" 0".

66 TASSY

operation which is self-contradictory. Parsimony is not related to taxa (constructions)
but to the evolutionary changes, that is hypotheses (here hypotheses of synapomor-
phy), which allow these constructions to be made.

Moreover, if character analysis is considered, a phyletic lineage implies that all
characters of ancestor-descendant populations or species are known. In paleontology,
this situation is the exception and not the rule, to say the least. If characters lacking
due to the fragmentary nature of fossils are considered, a phyletic lineage implies that
all these characters evolve without contradiction. Homoplasy, in the framework of
“mosaic of characters” (de Beer 1954:48) or heterobathmy (Hennig 1966), cannot
occur. As a result, this optimization goes further than the usual cladistic optimizations
of unknown data. Cladistic optimizations are subordinated to character distribution
on branching diagrams where homoplasy ts allowed.

Minimal length trees considered in their stratigraphic framework allow for testing
the adequacy of matches between cladistic events and the fossil record. Interesting
comparable patterns can be provided by taxa studied at different categorical levels,
with very variable time dimensions, and as different as trilobites (Edgecomb 1992),
coelacanths (Cloutier 1991), and mammals (e.g., Archibald 1993; MacFadden &
Hulbert 1988; Novacek 1992a; Tassy 1990; Werdelin & Solounias 1991).

Figure 7 shows the pattern of differentiation of Actinistia taken from Cloutier
(1991). I focus here on the sister groups labeled a and b. The extant coelacanth
(Latimeria chalumnae) belongs to monophyletic group b: (Hoplophagus (Macro-
poma, Latimeria)), the earliest known member of which is late Jurassic in age. Its
sister group (a) is already diversified in the early Triassic. The earliest member of
this group (the genus A/coveria) is separated by three dichotomies from more recent
taxa. When Alcoveria is compared to its more closely related taxa, the chronocline
appears to inversely reflect the morphocline. Taxa that branched earlier all appear
later in the fossil record. This situation is comparable to that shown in Figures 5 and
6. The stratigraphical gaps are considerable, for (Hoplophagus (Macropoma, La-
timeria)) more than 30% of the postulated time range (that is, 50 million years). To
arrange the nine actinistian taxa so that they match with the stratigraphical sequence
would alter six of the seven dichotomies.

The temporal cladogram of proboscideans shows a comparable pattern (Figure 8).
This tree is based on the data matrix published by Tassy (1990) with some modifica-
tions: two characters were added to the original 136 characters, and new observations
modified the mapping of seven characters. The tree displayed in Figure 8 is the strict
consensus tree of three trees selected by successive weighting from 30 equally
parsimonious trees (each of these 30 trees is 224 steps long, CI = 0.74, RI = 0.90).
Successive weighting is an algorithm that gives a posteriori weight to characters
according to their consistency and retention indexes. The consensus tree of the 30
equally parsimonious trees contains two multifurcations for nodes 10-13 and 15-17.
These multifurcations point to uncertainties in the pattern of differentiation of
Miocene Elephantoidea. In all cases (including the tree selected by successive
weighting depicted by Figure 8) the postulated time-range of sister-groups shows
considerable gaps. For example, sister-group relationships of Moeritherium imply an

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PALEONTOLOGY AND PHYLOGENY

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inferred range extension that covers 75% of the total range. Meanwhile, 53% and
62% of the respective ranges of Tetralophodon and of elephantids are inferred. The
mammalian fossil record from the Miocene is often acknowledged to be fairly good.
If the cladogram of Proboscidea is correct, the range of most of the tetralophodont
taxa (node 14) shows a very poor record. Because of the sister-group relationship
between elephantids and stegodontids (Stegolophodon, Stegodon) (node 18), a gap

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PALEONTOLOGY AND PHYLOGENY 69

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of five million years between 13 Ma and 8 Ma was previously assumed (Tassy 1990).
A recent discovery from the early Miocene of Thailand (Tassy et a/. 1992) made the
known range of Stegolophodon three to six million years older; consequently the
inferred range of the elephantids is equally increased. Stegolophodon is a paraphyletic
genus, a stem genus for Stegodon. Perhaps it is a stem genus for all tetralophodont
forms and hypothesized nodes should be reconsidered; the gaps which affect tetralo-
phodont taxa would be reduced. The discovery of this very early stegolophodont
species yields an empirical demonstration that the fossil record is not adequate.
Consequently, gaps are not sufficient to allow us to alter unambiguously a branching
sequence obtained by parsimony procedures. The radiation of tetralophodont forms
could have taken place in the late Early Miocene and not the late Middle Miocene as
previously thought. Although we can surmise that more complete material of Early
Miocene age will again change the cladogram, Figure 8 is the best fit to the data on
the present evidence. (See more recent developments in Tassy 1994).

The cladistic analysis at the species level of North American equids (MacFadden
& Hulbert 1988) shows again the same pattern (Figure 9). For example, sister-group
relationships between the Pliohippus mirabilis lineage (number 5 in Figure 9) and
the clade including Equus (the “Astrohippus-Dinohippus clade” of MacFadden &
Hulbert, number 4 in Figure 9) implies that more than 40% of range is inferred. If
one considers the details of Astrohippus-Dinohippus (not seen here), the morphocline
contradicts the chronocline. The earliest known taxa (early Hemphillian) branched

70 TASSY

later than the later known ones (late Hemphillian) (Hulbert 1989). Here again the
polarity based on stratigraphy is at odds with cladistic hypotheses of polarity.

On the other hand, during a time range of eight millions years during the
Paleocene, pterychtid ungulates studied at the species level show a better fit between
the cladogram and the stratigraphical record (Archibald 1993). In this example,
Archibald uses Donoghue’s concept of “metaspecies” (Donoghue 1985; De Queiroz
& Donoghue 1988). Use of “metaspecies” (= “clade without autapomorphies” ac-
cording to Archibald) leads to study of modes of speciation through the temporal
cladogram of pterychtids. As a clade can only be recognized by the presence of one
autapomorphy, a “clade without autapomorphies” is only meaningful if one accepts
the idea that the fossil record is fairly complete, so that a paraphyletic grouping
situated between two nodes of the cladogram exemplifies an ancestral species: a
“metaspecies.” Such an approach leads Archibald to identify modes of speciation:
budding and anagenetic speciation. The cladogram of pterychtids contains 23 di-
chotomies; only 9 show stratigraphical gaps, and only four of them are so important
that the sister-group relationships viewed in the stratigraphical context show the
putative descendant older than the putative ancestor. As Archibald (1993) concludes
“either the fossil record is incomplete, or the cladistic analysis is incorrect. For
heuristic purposes the latter opinion is not recognized.” Said differently, only the
cladistic procedure allows us to identify such cases.

If we are faced by some incongruence between cladistic sequence and known
stratigraphical sequence, when do we decide to change the cladistic sequence? What
is the ultimate evidence that allows us to do it? One answer is stratocladistics (Fischer
1988, 1992). Stratocladistics is based on the minimization of lineages and favors
ancestor-descendant relationships. A counterpart is the increase in extra steps, that 1s
unnecessary homoplasy. Still, there is no rationale for minimizing taxic diversity. No
general rule has yet been provided — and I see none — to balance the number of
steps implied by cladistic analysis and the postulated gaps in the geological record,
if any. These belong to separate universes.

Recent developments on this topic (e.g., Huelsenbeck 1994; Salles 1995) are based
on the separation of extrinsic data (time, space) from intrinsic data (shape).
Cladograms are taken as guides to estimate the quality of the fossil record. In turn,
different indices quantify the fit of the cladogram to the stratigraphy. Minimizing
gaps in the fossil record (= minimizing “ghost lineages”) can be a tool for choosing
between different minimal length trees. Another way is to select non-parsimonious
trees because they better fit the fossil record, even if such a procedure is based on
careful statistics (e.g., Wagner 1995). In that case the data (maximized homologies
of the minimal length tree) are subordinated to the stratigraphic record. But no general
rule is known to quantify unambiguously the quality of the record. In that case, the
choice is based on vague premises such as the assumption that the record is thought
to be sufficiently good to allow alterations of the cladistic result.

From these examples, can we decide when a match between stratigraphy and
cladistic branching is due to chance and when it is not ? | venture to conclude that

PALEONTOLOGY AND PHYLOGENY 71

the inequality of the fossil record precludes any general rule for assessing when
inadequacy is due to the possible defects of parsimony procedures.

Hominids and Concluding Remarks

The examples cited above demonstrate that stratigraphical occurrence alone
cannot be used to assess polarity of characters and, consequently, relationships.
Fossils have never been dismissed by cladistic analysis. On the contrary, they can be
presented “as critical data for phylogeny” (Novacek 1992b). The emerging number
of cladograms drawn in the stratigraphical framework but conceived only with the
use of the outgroup criterion is a consequence of the nature of cladistics. Cladograms
are based only on intrinsic data and are independent of extrinsic data such as known
temporal range. Hence, a confrontation between the two kinds of data is possible
(Norell 1992).

Phylogenetic inquiries dealing with hominids are not different from those dis-
cussed above. Early hominids were already diversified between 3 and 2 million years
ago, whatever the phylogenetic hypotheses are. Three species (and perhaps more;
Wood & Turner 1995) were probably contemporaneous two million years ago: two
robust australopithecines and one species of the genus Homo. Taxic diversity oc-
curred. The systematic pattern within the genus Homo itself is also probably a tree
and not a single lineage. Let us consider Figure 10, a parsimony analysis of eleven
characters taken in the genus Homo (Stringer 1987), a classic of the paleoanthro-
pological literature. If the cladogram is viewed as a phylogenetic tree, the evolution
of Homo displayed taxic diversity; Homo erectus is a grade, as is Homo habilis. The
species Homo sapiens is only a clade (node 3 of Figure 10) if it includes the two
geographic populations of Homo erectus. According to Stringer (1987) a tree closer

FIGURE 10. Sister-group relationships within the genus Homo (strict consensus tree, length
= 43 steps, CI = 0.74). Taken from Stringer (1987).

72 TASSY

to the stratigraphic sequence — 1n which “early archaic sapiens” becomes the sister
group of node 6 of Figure 10 — costs three extra steps. Nevertheless, this tree could
not be entirely changed into an anagenetic lineage (as in Figure 3), since diversity
occurs among sapiens: Neandertals and fossil Homo sapiens sapiens (“Skhul-Qafzeh
people” of node 7 of Figure 10) were contemporaneous. Nevertheless, to choose the
longer tree depends on confidence in the completeness of the fossil record. To choose
the shortest tree (Figure 10) depends on confidence in the matrix: this tree reflects
the best fit to the data.

Cladistic procedures are said to have severe limits, and, relative to human
evolution, “abundant biological limitations” (Trinkaus 1990), Still, | am not aware
of any method devoid of limitations, or, better said, of prerequisites. According to
Trinkaus (1990:4), cladistics can never be more than an approximation of reality
because it is based on the principle of parsimony. Certainly we all wish to know what
is real in our historical reconstructions. Nevertheless, science is a means to produce
heuristics and representations of reality. The relation between the real world and our
representation of it is an epistemologic debate into which | will not go further.
Anyway, | doubt that any phylogenetic hypothesis of any sort can be more than an
approximation of reality. A lineage is not a biological reality, it is a representation, a
construction based on hypotheses, and so also are sister groups. Trinkaus’ (1990:9)
alternative to cladistics applied to human evolution 1s to “regard the available fossil
samples (or specimens) as representative of prehistoric populations or lineages acting
as portions of dynamic evolutionary units.” Here we are left with the phylogenetic
challenge we have discussed throughout these pages: the identification of “lineages,”
“portions,” and “units” through reconstruction procedures.

My conclusion will be a very crude one. Paleontological data are morphological
data. As such, their phylogenetic analysis cannot be distinguished from that of
neontological data. Consequently, paleontological data can be analyzed in many
different ways; cladistics is one of these if the aim is the reconstruction of phylogeny
through character analysis. Cladistic analyses through parsimony procedures with
computer programs, like PAUP (Swofford 1993) or Hennig86 (Farris 1988), have
been performed for various groups of mammals, including those nearly entirely fossil.
I see no reason why a mammalian group, of any rank, including Primates or even
Homo (e.g., Bonde 1977; Stringer 1987), would ontologically resist the quest for
clades.

Acknowledgements

I thank Dr. L. S. Cordell, D. W. Stratmann, and the organizing committee of the
Paul L. and Phyllis Wattis Foundation Endowment Symposium for inviting me to
present a paper at the California Academy of Sciences. Deborah W. Stratmann’s
patience and efficiency were particularly appreciated. Writing the manuscript prof-
ited from Dr. D. Goujet, Dr. V. Barriel, and D. Visset’s help. Figures 7, 9, and 10
were reproduced courtesy of Drs. R. Cloutier, B. MacFadden, and C. Stringer. The
final manuscript was carefully edited by Dr. E. Meikle. | especially thank Prof. F.

PALEONTOLOGY AND PHYLOGENY 7h

Clark Howell for comments and suggestions on an early draft of the manuscript, and
Dr. J. D. Archibald for extremely helpful criticisms. Errors remain mine.

Literature Cited

Archibald, J. D. 1993. The importance of phylogenetic analysis for the assessment of species
turnover: A case history of Paleocene mammals in North America. Paleobiology 19:1-27.

Bonde, N. 1977. Cladistic classification as applied to vertebrates. Pages 741-804 in M. K.
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Homoplasy, Clades, and
Hominid Phylogeny

Henry M. McHenry
Department of Anthropology

University of California
Davis, CA 95616

Early hominid species share many unique traits, but some of these resemblances
apparently evolved independently in separate lines of descent. Such parallel
evolution is called homoplasy. Homoplasy tends to obscure phylogenetic relation-
ships. Cladistic analysis helps clarify this obscuration. It also helps reveal assump-
tions, biases, and other problems associated with reconstructing our family tree.
The resulting phylogeny shows an unexpected pattern with extensive parallel
evolution in two lineages of “robust” australopithecines and a close relationship
between later “robust” australopithecines and early Homo.

“For animals, belonging to two most distinct lines of descent,” wrote Darwin
(1859:427) “may readily become adapted to similar conditions, and thus assume a
close external resemblance.” He went on to warn “but such resemblances will not
reveal — will rather tend to conceal their blood-relationship to their proper lines of
descent.” The fin-like limbs of whales and fishes, he observed, resemble each other
not because of common descent but as adaptations for swimming. The resemblance
is due to convergent or parallel evolution and not to inheritance from a common
ancestor. The independent evolutionary appearance of a trait in two or more taxa,
where the trait is not inherited from a common ancestor that also had that trait, is
referred to as homoplasy (see Sanderson (1991) for a recent review of homoplasy).
The wings of birds and bats are homoplastic. The opposable big toes of lemurs,
monkeys, and apes are not because this resemblance is due to inheritance from an
ancestor who also had this kind of grasping foot.

The idea is simple, but subtleties can obscure the distinction between resemblances
due to homoplasy and those due to common inheritance. In the sixth edition of On
the Origin of Species Darwin pointed out one reason for this. Closely related
organisms, he observed “have inherited so much in common in their constitution, that
they are apt to vary under similar exciting causes in a similar manner; and this would
obviously aid in the acquirement through natural selection of parts or organs strik-

Contemporary Issues in Human Evolution Memoir 21, Copyright © 1996
Editors, W.E. Meikle, F.C. Howell, & N.G. Jablonski California Academy of Sciences

78 MCHENRY

ingly like each other, independently of their direct inheritance from a common
progenitor” (Darwin 1872:427).

Among species of fossil hominids, some resemblances are due to homoplasy and
some are due to descent from a common ancestor that also possessed the trait. The
homoplastic resemblances are due to the fact that these species are so closely related
that they evolved similarities in parallel as they adapted to the same environments.
Homoplasy obscures attempts to find phylogenetic relationships. An excellent exam-
ple of this obscuration is the problem of interpreting the “Black Skull” (KNM-WT
17000).

When Alan Walker found this specimen in 1985 in 2.5 million year old deposits
in northern Kenya, there was little doubt that it belonged among the “robust”
australopithecines.! It shared with Australopithecus robustus and A. boisei a suite of
traits related to heavy chewing including huge cheek teeth, massive jaws, and heavily
buttressed skull to withstand the chewing forces. These resemblances imply close
phylogenetic affinity among these hominids, if these traits are due to descent from
an ancestor that also shared them. Most authors agree that the “robust” australopithe-
cines form a branch of our family tree that 1s quite separate from the lineage leading
to Homo (see Grine (1993) for an overview of current ideas). The Black Skull and
other “robust” hominids between 2.6 and 2.3 Ma form the base of this branch as the
species A. aethiopicus. The species from South Africa, 4. robustus (1.8-1[?] Ma), and
East Africa, A. boisei (2.2-1.3 Ma), are the terminal parts of the “robust” branch.
Relative to other contemporary hominid species, they form one branch, or, more
precisely, they are monophyletic. They share a similar complex of features related to
heavy chewing. Their faces, cranial vaults, jaws, and teeth are strikingly similar in
many specific ways. Presumably they inherited these similarities from a common
ancestor so that these resemblances are homologous.

If the “robusts” are monophyletic with 4. aethiopicus at the base and A. robustus
and 4. boisei arising out of this common stem, then why do these later two species
resemble early Homo in so many ways? Early Homo and the later “robust” species
share numerous traits that are not present in 4. aethiopicus. These resemblances
include brain expansion, flexion of the cranial base, reduction of prognathism,
deepening of the jaw joint, and a host of other features. In fact, in many ways 4.
robustus and A. boisei resemble early Homo more than any of these resembles 4.
africanus (the 3-2 Ma South African “gracile” australopithecine). Perhaps these
resemblances are due to homoplasy. On the other hand, perhaps the resemblances
between 4. aethiopicus and the later “robust” australopithecines are due to homoplasy
and the “robust” species are not monophyletic.

This is a difficult paradox to resolve. Some of these resemblances are concealing
the true “blood-relationships to their proper lines of descent” to use Darwin’s
(1859:427) words. Clearly some procedure needs to be applied to parcel out ho-
moplasy ina way that makes assumptions and biases clearly visible. Many procedures
are available, but those developed by Willi Hennig (1966) have evolved into an
approach that has been effectively applied to this problem (Tassy this volume).
Although many extreme views have developed out of Hennig’s system (Hull 1988),

HOMINID PHYLOGENY 79

some fundamental features of what is commonly referred to as cladistics or phyloge-
netic analysis have proved to be very useful.

Cladistic Analysis

One useful feature of cladistic analysis is that when it is properly applied assump-
tions and biases are clearly revealed. At each step one has to expose one’s thinking
to critical analysis. This exposure safe-guards against the corrupting desire to advo-
cate a fixed position.

There are many ways to proceed in a cladistic analysis, but it is helpful to follow
a few basic steps. First, traits and species must be defined clearly. This step exposes
a flank for critics to attack, but insures that the practitioner has some depth of defense.
Paleospecies are hard to define, of course, and traits must be selected with special
care. Care means that the traits are selected without bias due to preconceived notions.
Care also must be given to the functional meaning of the trait. A paradox arises here
because the interpreter of the functional meaning of a feature may have a bias about
what the overall scheme of phylogenetic relationships “ought” to be.

A second step involves following the sequence of changes in the trait in the species
under study without regard to preconceived notions about the direction of change.
Brain size in human evolution increases through time, and there is no problem with
bias in that. Occlusal area of cheek teeth is medium in the earliest well known species
of hominid (A. afarensis), large in one of the next oldest species (A. africanus), huge
in the “robust” australopithecines that came after 4. africanus, and medium again in
the earliest Homo. This second step disregards time and preconception. The sequence
of changes in cheek tooth size places A. afarensis and the earliest Homo together.

The beauty of this formal procedure is that the practitioner is exposed at every
step to corrections kindly provided by colleagues. A third step, exposing even greater
vulnerability, consists of arranging the species according to where they fall from most
primitive to most derived. There are formal procedures for such ordering. Time
provides an imperfect clue (Tassy, this volume); usually the most primitive is the
earliest, but not always. A check is provided by comparing the expression of the trait
in closely related species which are not part of the analysis (outgroups, which for
hominid studies consist of non-hominid members of the ape and human superfamily,
Hominoidea). There are a variety of other methods of finding the direction of change
for each trait, but usually time and out-group tell a consistent tale.

At this point one has a trait list with the expression of each trait in a list of species
and a direction of change for each trait. From this one can derive a branching tree of
relationships (cladogram) for each trait. This procedure further exposes the practitio-
ner to scrutiny by doubting colleagues, although drawing a cladogram is quite
lock-step. One simply takes each trait individually, joins the two most derived species
by two intersecting lines, connects the next most derived species, and so on. The
simple diagram for each trait is meaningful. The two most derived species are united
by descent from a common ancestor which presumably also expressed the trait. So
simple it is, but so easily missed.

80 MCHENRY

The final step is to compile all the cladograms for all the traits and look for patterns.
Usually there are many different cladograms. Brain size and cheek tooth area in
hominid species produce two quite distinct patterns. Here again the cladist exposes
the weaknesses and strengths of the analysis for all to judge. The most common way
to resolve a conflict between cladograms 1s by choosing the one that requires the least
amount of homoplasy and is the most consistent with the data (i.e., the most
parsimonious).

Species, Traits, and States

There are many ways to divide up the hominid bone pile into genera and species;
compare, for example, Groves (1989), Tobias (1991), and Wood (1991). There is
general consensus that there are three species of “robust” Australopithecus (A.
aethiopicus, A. boisei, and A. robustus), but there are good reasons to accept a fourth,
A. crassidens (Howell 1978; Grine 1982, 1985, 1988). There are also good reasons
to give the “robust” australopithecines their own genus, Paranthropus (Grine 1988;
Clarke this volume), but perhaps such an honor is ill-advised because the “robust”
australopithecine species may not form a monophyletic group (Skelton and McHenry
1992; Walker et al. 1986; Leakey & Walker 1988; Walker & Leakey 1988). Reasons
have also been given to divide and/or re-sort 4. afarensis (e.g., Tobias 1980; Olson
1981; Ferguson 1983; Zihlman 1985; Senut & Tardieu 1985), 4. africanus (e.g.,
Clarke 1988; Kimbel & White 1988), and H. habilis (e.g., Groves 1989; Wood 1991).

Right at the start of a cladistic analysis one must lay the cards on the table and
reveal choices. To make any progress, it is useful to take the attitude that one 1s setting
up a hypothetical case in as reasonable a fashion as possible to find the logical
consequences. In what follows, early hominids are divided into five species of
Australopithecus. Early Homo is treated as a single species. Ardipithecus ramidus
(White et a/. 1994, 1995) and Australopithecus anamensis (Leakey et al. 1995) are
not included because they have not yet been fully described.

Australopithecus afarensis: The earliest (3.8-2.8 Ma) well-defined species is
difficult to appreciate fully because it has such a wonderful mixture of ape-like and
human-like qualities. Its skull is close to what one might expect in the common
ancestor of apes and people with an ape-sized brain (endocranial volume of 415 cc,
which is roughly the same as a chimpanzee and not at all like modern people who
average about 1350 cc), big muzzle, flat cranial base, flat jaw-joint, nasal sill, and
sagittal crest that is highest in the back. Its teeth bridge the gap between ape and
people with large central and small lateral upper incisors (ape-like), upper canine
reduced (human-like) but still large and with shear facets formed against the lower
premolar (ape-like), variable lower first premolar with some individuals having only
one strong cusp (ape-like) and others with some development of a metaconid cusp
(between modern ape and human), and parallel or convergent tooth rows (ape-like).
Their cheek teeth were quite large relative to their body weight. Postcranially, A.
afarensis is mostly human-like in having a hip, thigh, knee, ankle, and foot adapted
to bipedality. However, superimposed on this human-like body are many traits

HOMINID PHYLOGENY 81

reminiscent of the common ancestor such as somewhat elongated and curved fingers
and toes, a relatively short thigh, and backwardly facing pelvic blades. Sexual
dimorphism in body size is greater than in modern people, but not as high as in Gorilla
or Pongo. Males weighed about 45 kg and females 29 kg. They lived in a mixed
habitat, with some in well-watered and woodland conditions and others in more open
environments.

Australopithecus aethiopicus: This is the least well-known of all the species, but
the bits of fossils available appear to be sufficiently different to warrant separation
(Grine 1988; Kimbel e¢ a/. 1988; see Walker et a/. 1986 for a counter view). The
species aethiopicus was proposed on the basis of a partial mandible from Member C
of the Shungura Formation of Omo (Arambourg & Coppens 1967), but is best
represented by a nearly complete cranium (KNM-WT 17000: Walker ef a/. 1986).
These and isolated teeth span from 2.6 to 2.3 Ma. The cranium is much like 4.
afarensis in having an unflexed cranial base, flat jaw joint, strong prognathism, a
small cranial capacity (419 cc), and other traits. These primitive traits combine with
highly derived features associated with heavy chewing such as massive cheek teeth,
“dished” midface with zygomatics raked forward, a smooth transition between the
naso-alveolar clivus and the floor of the nose, a deep tympanic plate, and various
other traits which resemble later “robust” australopithecines. It also has a heart-
shaped foramen magnum like A. boisei.

Australopithecus africanus: Relative to A. afarensis and A. aethiopicus this
species has more Homo-like craniodental features.’ It is only known in South Africa,
and its age is only approximately established (3-2 Ma). Its vault is higher and more
rounded than the earlier species, its face is less prognathic, and its jaw joint is deeper.
The lower first premolars are bicuspid. Endocranial capacity is larger (442 cc).
Although the postcranium is much like 4. afarensis, the hand bones are more
Homo-like (Ricklan 1987, 1990). Body size resembles A. afarensis, although sexual
dimorphism appears to be slightly reduced with males weighing about 41 kg and
females 30 kg. The cheek teeth are larger than those of A. afarensis.

Australopithecus robustus: This species is also confined to South Africa. Its
geological age is only approximately known (1.8-1[?] Ma). Its craniodental morphol-
ogy is specialized for heavy chewing with very large cheek teeth, robust jaws, a flat
face with cheek bones raked forward, and a sagittal crest. However, it also has many
more Homo-like traits than earlier species: the brain is larger (530 cc), the face is not
prognathic, the cranial base is strongly flexed, the jaw joint is deep, and the hands
are more modern. They were relatively small-bodied (females weighed about 32 kg
and males only 40 kg). They lived in a relatively dry habitat in open grasslands.

Australopithecus boisei: This species derives from East African deposits from at
least 2.2 to 1.3 Ma. It is the most specialized for heavy chewing of all these species,
with massive cheek teeth, jaws, and supporting architecture of the cranium to
withstand the force generated by the huge chewing muscles. However, like 4.
robustus it possessed many Homo-like traits not seen in earlier species such as a larger

82 MCHENRY

brain (515 cc), flatter face, more flexed cranial base, and deeper jaw joint. Body size
is poorly known, but may have been about 34 kg for females and 49 kg for males.

Homo habilis: As Wood points out (this volume), there is evidence that there may
be two species represented among specimens attributed to 1. habilis, although Tobias
(1991) makes a strong case for just one. For the purposes of this study it is appropriate
to regard specimens from 2.4-1.6 Ma that have been referred to as Homo as a single
unit. Variability is high, but some consistent differences from Australopithecus are
apparent. Brain size is larger (631 cc average), vaults are more rounded and higher,
and cheek teeth are smaller. Body size for males may have been about 52 kg and for
females 32 kg.

Traits and States

Table | (Appendix A) lists 77 variable morphological traits and their expression
in each of these species and in an outgroup (extant great apes). The traits include 22
features of the face, palate, and zygomatic arch, 25 dental traits, 7 of the mandible,
10 of the basicranium, and 13 of the cranial vault. These can be grouped into five
functional complexes involving heavy chewing, anterior dentition, basicranial flex-
ion, prognathism/orthognathism, and encephalization. Skelton & McHenry (1992)
provide a full description and discussion of these traits and their functional meaning.
Strait e7 al. (in prep.) provide a revised and up-dated trait list including greater detail
on the expressions of these and other traits in chimpanzees, gorillas, and all species
of hominids except 4. ramidus and A. anamensis.

Morphoclines and Cladograms

The direction of evolutionary transformation for each trait (/.e., the polarity) flows
from primitive to derived. The outgroup (i.e., great apes) determines the primitive
pole unambiguously for all of the craniodental traits in this study. For example,
endocranial volume is 385 ce in Pan (outgroup), 415 ce in A. afarensis, 419 ce in A.
aethiopicus, 442 ce in A. africanus, 515 cc in A. boisei, 530 cc in A. robustus, and
631 in early Homo. This sequence is the polarized morphocline. It implies that early
Homo and A. robustus are the most highly derived for this trait and can be joined as
sister taxa relative to all other species. Their joint line connects next to 4. boisei to
form a group of three species who are derived relative to all other species. The process
continues until all groups are connected into a cladogram as shown in Figure 1.

The simplicity and straightforwardness of this procedure allows for conflicting
evidence. For example, unlike endocranial volume, cheek tooth area goes from 294
mm? in the out-group, to 460 mn in A. afarensis, to 479 mm in early Homo, to 516
mm? in A. africanus, to 588 mm in A. robustus, to 688 mm in A. aethiopicus, to 799
mm? in 4. boisei. This results in the cladogram displayed in Figure 2, which is
incompatible with the cladogram in Figure 1. To choose the one that most likely
reflects the true evolutionary relationships, one must use the principle of parsimony.

HOMINID PHYLOGENY 83

OUTGROUP OUTGROUP
AFARENSIS AFARENSIS
AETHIOPICUS AETHIOPICUS
AFRICANUS BOISEI
BOISE ROBUSTUS
ROBUSTUS AFRICANUS
HOMO HOMO

FIGURE |. Cladogram implied by the polar- FIGURE 2. Cladogram implied by the polar-
ized morphocline based on endocranial vol- ized morphocline based on cheek tooth area.
ume.

Parsimony

The theory of parsimony is the subject of much discussion (see Sober 1988 for a
review), but fundamentally it is quite straightforward. To deal with the conflicting
evidence revealed by incompatible cladograms, parsimony assumes that the true
phylogeny resulted from the fewest evolutionary steps. There are various measures
of parsimony. The most commonly used measure is the consistency index, which is
simply the minimum number of steps possible divided by the actual number of steps.
If no homoplasy were present the consistency index would equal 1.

The most parsimonious cladogram that can be constructed out of the 77 traits
described in Skelton & McHenry (1992) is the one shown in Figure 3. The two most
derived taxa are A. robustus and A. boisei, whose stem joins Homo to form the next
most derived group relative to the other species. The A. robustus/A. boisei/Homo
clade then joins 4. africanus, and that stem next joins A. aethiopicus. A. afarensis
forms a sister clade to all other hominids. The consistency index is 0.722 when all 77
traits are used. This is also the most parsimonious cladogram when traits are grouped
into anatomical regions or functional complexes. A cladogram linking A. aethiopicus
to A. boisei and A. robustus as one branch and A. africanus/early Homo as another 1s
slightly less parsimonious (CI = 0.69) using this trait list. Strait ef a/. (in prep.) show
that with a revised trait list this cladogram is slightly more parsimonious than that in
Figure 3.

84 MCHENRY

OUTGROUP Our Family’s Phylogeny

Figure 4 displays the phylogenetic tree
implied by the most parsimonious
cladogram. This phylogeny suggests that
A. afarensis 1s the most primitive hominid
and that all later hominids shared a com-
mon ancestor that was more derived than
A. afarensis. This post-afarensis hypo-
thetical ancestor may someday be discov-
ered. Its morphology can be
reconstructed by observing the many
ways A. aethiopicus resembles later
hominids (especially 4. africanus) and
not 4. afarensis. For example, the upper
canine jugae are prominent in the out-
group and in 4. afarensis, but reduced or
absent in all other species of hominid,

HOMO which implies that the common ancestor

FIGURE 3. The most parsimonious Of all post-a/arensis species had jugae
cladogram using all 77 traits, or using summary that were also reduced. This hypothetical
scores from the analyses of five functional com- ancestor would have a strongly devel-
plexes or seven anatomical regions. oped metaconid on P3. It would not, how-

ever resemble 4. aethiopicus in traits
related to masticatory hypertrophy (heavy chewing), nor would it resemble any other
post-afarensis species because they are all too derived in basicranial flexion, orthog-
nathism, and encephalization to have been the ancestor of 4. aethiopicus.

After the divergence of A. aethiopicus, this phylogeny depicts a common ancestor
of A. africanus, A. robustus, A. boisei, and Homo which resembled A. africanus in its
development of anterior dentition, basicranial flexion, orthognathism, and encephali-
zation. A second hypothetical common ancestor appears in Figure 4 to account for
the numerous derived traits shared by 4. robustus, A. boisei, and early Homo which
are not seen in 4. africanus. This ancestor would have the degree of basicranial
flexion and orthognathism seen in early Homo and the amount of encephalization
seen in A. robustus and A. boisei. This phylogeny proposes a third hypothetical
ancestor which would be at the root of the lineage leading to 4. robustus and A. boisei.
This ancestor probably resembled 4. robustus in traits related to heavy chewing.

These results imply that there was a large amount of parallel evolution in our
family tree. The most conspicuous case of parallel evolution involves heavy chewing
in A. aethiopicus, A. robustus, and A. boisei. This phylogeny suggests that the specific
resemblances between A. aethiopicus and the later “robust” australopithecines are
not due to descent from a common ancestor that had these traits, but due to
independent acquisition. This is a very surprising result. The “Black Skull” looks so
much like 4. hoisei that its discoverers and original describers attributed it to that

AFARENSIS

AETHIOPICUS

AFRICANUS

ROBUSTUS

BOISE!

HOMINID PHYLOGENY 85

2.0 mya a
Homo A. robustus A.boisei
robustus-like
africanus -like ancestor
2.5 mya ancestor
Cr» @
\ — <= A
SS a>
A. africanus _ A. aethiopicus
3.0 mya
aethiopicus-like
ancestor
@&
3.5 mya a |
A. afarensis
2 mya

FiGure 4. The phylogeny implied by the most parsimonious cladogram. Three hypothetical
ancestors are predicted.

species and not to 4. aethiopicus (Walker et al. 1986; Leakey & Walker 1988; Walker
& Leakey 1988). For example, both have extreme anterior projection of the zygo-
matic bone, huge cheek teeth, enormous mandibular robusticity, a heart-shaped
foramen magnum, and temporoparietal overlap of the occipital at asterion (at least in
males).

However, all of these traits except for the heart-shaped foramen magnum are
related to the functional complex of heavy chewing. The huge cheek teeth and robust
mandibles of both species are obviously part of masticatory hypertrophy. The anterior
projection of the zygomatic bones brings the masseter muscles into a position of
maximum power. The encroachment by the root of the zygomaticoalveolar crest
obscures the expression of the anterior pillars and upper canine jugae. Even the
morphology of the temporoparietal overlap with the occipital is related to the function
of the forces generated by the chewing muscles (see Skelton & McHenry 1992 for
details).

86 MCHENRY

Theoretically, it is understandable how such detailed similarity could be due to
parallel evolution. This is an example of what Darwin (1872:328) referred to as
species which are closely related and share “so much in common in their constitution”
that similar selective forces produce similar morphologies. The selective forces in
this case are related to a feeding adaptation which is associated with a specialized
ecological niche. As Mayr (1969:125) points out, “Most adaptations for special
niches are far less revealing taxonomically than they are conspicuous. . . Occupation
of a special food niche and the correlated adaptations have a particularly low
taxonomic value.” In fact, many of the same traits characteristic of A. aethiopicus
and the other “robust” australopithecines reappear in distantly related species which
are adapted to heavy chewing. Expansion of the cheek teeth, shortening of the muzzle,
and anterior migration of the attachment areas of the chewing muscles are seen in
other primates whose diet requires heavy chewing (e.g., Hadropithecus, Theropi-
thecus, probably Gigantopithecus, and Ekgmowechashala).

Although the most parsimonious cladogram implies this phylogeny, other
cladograms are possible but less probable. A cladogram linking A. aethiopicus to A.
boisei and A. robustus as one branch, and A. africanus/early Homo as another,
requires more evolutionary steps in this analysis because the later “robusts” resemble
early Homo in so many features (but see Strait e¢ al. (in prep.) for a different view).
These include many aspects of basicranial flexion, loss of prognathism, changes in
the anterior dentition, and encephalization. The postcrania, although not included in
this analysis, support the view that at least 4. robustus and early Homo are mono-
phyletic relative to other species of early hominid.

Whatever the true phylogeny is, and there can be only one, the fact remains that
homoplasy is commonplace. There is no avoiding it. Some resemblances appeared
independently and not because of evolution from a common ancestor that possessed
the same feature. Either adaptations for heavy chewing evolved twice or basicranial
flexion, orthognathism, reduced anterior dentition, and encephalization evolved more
than once. Darwin’s astute observations apply to our own family tree.

One general lesson from this approach to hominid evolutionary biology is how to
deal with ambiguity. As the King of Siam said in Rodgers and Hammerstein’s The
King and I, “What was so was so; what was not was not,” but now “some things
nearly so, others nearly not.” Itis acommon experience, although perhaps uncommon
to have such a clear example of ambiguity as provided by the hominid fossil record.
Either heavy chewing resulted in the independent evolution of 4. aethiopicus and A.
robustus/A. boisei, or other forces shaped A. boisei, A. robustus, and early Homo to
resemble each other in encephalization, basicranial flexion, anterior dentition, and
orthognathism.

From this point of view it is not particularly useful to advocate a fixed position.
One needs to make the best of our tiny sample of life in the past, to be open to new
discoveries and ideas, and to enjoy the pleasure of learning and changing.

HOMINID PHYLOGENY 87

Acknowledgements

I thank the organizers of this symposium and particularly D. Stratmann and F. C.
Howell for the invitation to contribute this paper. I am indebted to my colleague, R.
R. Skelton, with whom I did the analysis that resulted in the conclusions expressed
here. | am grateful to David Strait for permission to cite his manuscript which provides
a valuable reanalysis of the traits, states, and species presented here. | thank all those
whose work led to the discovery of the fossils, and especially the late L. S. B. Leakey,
M. D. Leakey, R. E. Leakey, M. G. Leakey, F. C. Howell, D. C. Johanson, F.
Thackery, C. K. Brain, P. V. Tobias, T. White, B. Asfaw, Alemu Ademasu, and
Solomon Wordekal for many kindnesses and permission to study the original fossil
material. I thank the curators of the comparative samples used in this study. Partial
funding was provided by the Committee on Research of the University of California,
Davis.

Endnotes

' This phrase, “robust” australopithecines, refers to early hominids that have specializa-
tions for heavy chewing. Various taxonomic names are associated with these fossils including
Paranthropus robustus (from the South African site of Kromdraai; Broom 1938), Paran-
thropus crassidens (from Swartkrans, South Africa; Broom 1949, 1950), Zinjanthropus boisei
(Olduvai Gorge, Tanzania; Leakey 1959), and Paraustralopithecus aethiopicus (Omo, Ethio-
pia; Arambourg & Coppens 1967). They are very similar to one another in features related to
heavy chewing, and many authors prefer to recognize their similarity by designating them as
a separate genus, Paranthropus (e.g., Robinson 1972; Grine 1993; Clarke, this volume).

> The sample comprising A. africanus is heterogeneous and some specimens may belong
to early Homo (e.g., Sts 19 according to Kimbel & Rak 1993). The removal of Sts 19 from the
sample does not affect the results of the analysis reported here. The Homo-like traits reported
by Kimbel and Rak of Sts 19 do not change the scores of the relevant characters in Table |
(7.e., #57, 58, 59, 61) since there are other specimens of A. africanus that are Homo-like (e.g.,
Sts 71, Stw 30, MLD 37/38) in their expression of one or more of these characters.

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90 MCHENRY

APPENDIX A

TABLE 1. Craniodental Characteristics of Early Hominid Species!

Species” and States® (nd = no data)

Characters* A B c D E F G

FACE

1. Nasion approaches glabella 0 0 0 | | 1 1

2. Location of the greatest width of the nasal bones 0 1 2 0 ys 2 0

3. Inferior orbital margin rounded laterally 0 0 l 0 | 0 0

4. Infraorbital foramen location 0 0 1 0 1 | 0

5. Multiple infraorbital foramina present 0 0 2 1 2 2 2

6. Anterior pillars 0 0 3 | | 3 2

7. Upper canine jugae presence and prominence 0 0 4 1 2 4 3

8. Upper canine jugae independent of margin of 0 0 2 2 2 2 1
nasal aperture

9. Projection of nasoalveolar contour beyond 0 0 2 l 2 2 1
bicanine line

10. Distinct subnasal and intranasal components 0 0 3 2 3 3 1
of nasoalveolar clivus

11. Anterior projection of the subnasal region 0 0 0 1 z 2 2
relative to the nasal aperture

12. Nasoalveolar clivus convexity 0 0 | 2 4 4 a)

ZYGOMATIC ARCH

13. Robusticity of zygomatic bones 0 1 3 2 3 3 0

14. Relative height of anterior masseter origin 0 1 5 4 2 0
by zm-alv/orb-alv index

15. Zygomaticoalveolar crest weakly arched in 0 0 2 2 2 | 0
frontal view

16. Anterior projection of zygomatic bone 0 0 4 2 3 4 |

17. Position of anterior edge of zygomatic 0 | 2 2 3 3 2
process origin

ANTERIOR DENTITION

18. Deciduous canine shape 0 | nd 2 2 Pi 2

19. I! incisal edge length 0 0 nd | 2 2 |

20. Position of I? roots relative to margins of 0 0 I | | | |
nasal aperture

21, Projection of upper canine 0 1 nd 2 3 3 3

22. Upper canine labial crown profile 0 0 nd | 2 2 2

23. Mesial and distal contact facets on upper canine 0 0 nd | | l |

24. Mesial occlusal edge shape of lower canine 0 0 nd | l l |

25. Prominence of lingual ridge on lower canine 0 0 nd | | | 2

26. Lower canine distal occlusal edge length 0 1 nd 2 3 3 3

27. Frequency of mandibular diastema 0 l 3 2 3 3 2

POSTERIOR DENTITION

28. Postcanine tooth area (sq. mm) 0 1 5 3 4 6 2

29. Deciduous M, distal crown profile 0 1 nd 3 4 4 2

30. P§ occlusal outline 0 0 3 | 3 3 2

31. Separation of P4 cusp apices 0 | nd 3 4 4 2

33. P3 talonid height relative to protoconid 0 1 3 2 3 3 2

34. Degree of development of “robust” features of P3 0 1 4 2 5 6 3

35. Mandibular P3 M-D length/B-L breadth index 0 1 4 2 3 3 1

HOMINID PHYLOGENY

TABLE | (continued). Craniodental Characteristics of Early Hominid Species!

Characters*

Species” and States* (nd = no data)

POSTERIOR DENTITION (continued)
36. P3 occlusal crown outline
37. P3 occlusal wear relative to other postcanine teeth
38. Predominant P3 root conformation
39. Degree of development of “robust” features of P4
40. Degree of mesial appression of M; and M2
hypoconulids
41. Degree of lower molar cusp swelling
42. Wear disparity between buccal and lingual
molar cusps

oooco

o-r-ooco

—

Waw —

NmwnNn-——

PALATE

43. Flat, shallow palate

44. Index of palate protrusion anterior to sellion

45. Index of Overlap

46. Angle between sellion-prosthion and
Frankfurt horizontal

47. Index of palate protrusion to masseter

oooco

i=)

oe So

one

MANDIBLE

48. Mandible robusticity

49, Orientation of mandibular symphysis

50. Position of mental foramen relative to mid corpus
51. Direction of mental foramen opening

52. Hollowing above and behind the mental foramen
53. Width of mandibular extramolar sulcus

54. Height of mandibular ramus origin on corpus

ooooocco

ONWNN NY

NNwWN PSHE HE

ween

ies)

MmMmeryem &

—oO

BASICRANIUM

55. Flexion of cranial base

56. Distance between M3 and the temporo-
mandibular joint

57. Depth of mandibular fossa

58. Position of postglenoid relative to tympanic plate

59. Orientation of tympanic plate

60. Shape of tympanic canal

61. Angle of petrous bones relative to coronal plane

62. Heart shaped foramen magnum

63. Inflection of mastoids beneath cranial base

64. Inclination of nuchal plane

cm bh)

ooooccocoo

eas
Ca

NNK ONNOS

om f NH Ninh

ined

to th

no -—-f$hENN

—-fhRNN

i=)

Ww he

CRANIAL VAULT

65. Cranial capacity (ml)

66. Cerebellar lobes “tucked under” cerebrum,
without lateral flare or posterior protrusion

67. Branch of middle meningeal artery from
which middle branch is derived

68. Occipital-marginal drainage system present in
high frequency

69. Supraorbital tori in form of “costa supraorbitalis”

70. Temporal lines converge to bregma

te th

92 MCHENRY

TABLE | (continued). Craniodental Characteristics of Early Hominid Species!

Species” and States® (nd = no data)
Characters4 A B C D Bs F G

CRANIAL VAULT (continued)

71. Sagittal crest present, at least in males 0 0 0 | 0 0 |

72. Size of posterior relative to anterior part 0 1 1 2 3 3 3
of temporalis

73. Compound temporal/nuchal crest 0 0 0 2 2 | |

74. Asterionic notch present 0 0 0 1 | | |

75. Temporoparietal overlap of occipital at asterion, 0 0 | 0 0 | 0
at least in males

76. Pneumatization of temporal squama 0 0 0 2 2 | y)

77. Mastoid processes inflated and projecting lateral 0 0 2 | 2 2 0

to supramastoid crest

! This is an abridged version of Table | in Skelton & McHenry (1992).

2 Species are A = Outgroup (Great Apes), B = 4. afarensis, C = A. aethiopicus, D = A. africanus, E = A
robustus, F = A. boisei, G = early Homo.

3 States are ordered multistate characterizations.

4 Characters are grouped into anatomical regions where face is 1-12, zygomatic arch is 13-17, anterior

dentition is 18-27, posterior dentition is 28-42, palate is 43-47, mandible 1s 48-54, basicranium 1s 55-64,
and cranial vault is 65-77.

The Genus Paranthropus:
What’s in a Name?

Ronald J. Clarke

Palaeoanthropology Research Unit
Department of Anatomical Sciences
Medical School

University of the Witwatersrand
Johannesburg, South Africa

The hominid genus Paranthropus was first recognized and named by Robert
Broom. Subsequent studies, especially by John T. Robinson, demonstrated that
South African members of this genus possessed a highly specialized dentition,
massive mandible, and related cranial architecture, all seemingly associated with
a dietary adaptation which separated them from members of the Australopi-
thecus/Homo lineage. Later discoveries in East and South Africa allow us to
recognize at least five species of Paranthropus: P. robustus, P. crassidens, P. boisei,
P. aethiopicus, and an as-yet unnamed species from Sterkfontein. The species of
Paranthropus are united by their dietary specialization related to crushing and
grinding hard foods, especially in dry environments. This specialization is reflected
in the morphology of their cheek teeth and a cranial architecture designed to
maximize the force applied through those teeth. The oldest known species of
Paranthropus, present about 2.5 million years ago in East Africa, still retained large
anterior teeth, which were greatly reduced by 2 million years ago. Paranthropus
represents a well-adapted hominid clade which co-existed with our ancestral
lineage for at least 1.5 million years.

On Tuesday, 14 June 1938, Dr. Robert Broom recovered from Kromdraai, near
Sterkfontein in South Africa, the fossilized fragments of a partial skull that was to be
the first find of a bizarre form of man that we now know to have existed in South
Africa, Tanzania, Kenya, and Ethiopia during the period between 2.5 million and |
million years ago. In his description of the new specimen, Broom (1938) noted that
the face was flat, the incisors and canines small, the molars different in shape from
those of the known small sample of Sterkfontein ape-men, and the upper P4 was larger
than that of the Sterkfontein Australopithecus. On this basis, he “confidently” placed
the skull into a new genus and species, Paranthropus robustus, meaning a robustly
built form of man that paralleled the main line of human development. Later, Broom
(1939) commented on “the remarkable degree of flattening of the lower part of the
face above the incisors and canines,” noting that it was mainly on this feature that he

Contemporary Issues in Human Evolution Memoir 21, Copynght © 1996
Editors, W.E. Meikle, F.C. Howell, & N.G. Jablonski California Academy of Sciences

94 CLARKE

made it the type of a new genus. Subsequent and more complete discoveries of the
same form of man from Swartkrans (Broom & Robinson 1952), Olduvai (Leakey
1959), Peninj (Leakey & Leakey 1964), Omo (Howell 1969), Lake Turkana (R. E.
F. Leakey et al. 1971), and Chesowanja (Carney ef al. 1971) not only justified
Broom’s confidence but also demonstrated that Paranthropus was an extremely
bizarre and apparently highly specialized primate. Louis Leakey (1959) went so far
as to place his hyper-robust cranium from Olduvai into a distinct genus, Zinjan-
thropus, and Arambourg & Coppens (1968) created the genus Paraustralopithecus
to accommodate an early specimen from Omo in Ethiopia.

While most researchers agreed that the specimens labeled as Paranthropus indeed
represented an unusually massive-jawed type of hominid, they did not all agree that
generic distinction from Australopithecus was justified. At the time when only the
Kromdraai specimen was known, Simpson (1945) considered Paranthropus to be
merely a subgenus of Australopithecus. Even after the discovery of more complete
specimens from Swartkrans in 1948, Simpson’s view was followed by Oakley (1954),
Howell (1955, 1968), Leakey er al. (1964), and Simons (1967). Doubt had been
expressed by Dart (1948a and b) about the generic distinction of Paranthropus, which
in 1951 was lumped into Australopithecus by Washburn & Patterson. Others who
followed this classification were Le Gros Clark (1955), Dobzhansky (1962), Camp-
bell (1963), Pilbeam & Simons (1965), Tobias (1967), Wallace (1972), Brace (1973),
von Koenigswald (1973), Wolpoff (1974), Wolpoff & Lovejoy (1975), and, since
then, most other authors on the subject.

Broom’s view on the generic distinction of Paranthropus was, however, rigor-
ously supported by the work of John Robinson (1952, 1954a and b, 1956, 1962, 1963,
1967, 1972), who not only gave sound morphological reasons for so doing but also
(1962) attributed the unique cranial architecture of Paranthropus to its specialized
dentition, which he said must be related to dietary specialization. In 1977, after
detailed analysis of the craniofacial anatomy of Paranthropus, Australopithecus, and
Homo, | found that there was no reason to dispute Broom’s and Robinson’s view on
the generic distinction of Paranthropus, and | gave a list of 20 apomorphous
(specialized) characters of Paranthropus (Clarke 1977, 1985), as follows. This
definition is based on that given by Robinson (1962), with additions by the present
author.

The Genus Paranthropus

Paranthropus is a genus of the family Hominidae characterized by the following
apomorphous characters in the cranium when compared to other genera within the
family:

1) A brain that is on the average larger than that of Australopithecus, yet not as large
as that of Homo.

2) Formation of a lightly concave, low forehead with a frontal trigone delimited later-
ally by posteriorly converging temporal crests.

3) Presence of a flattened “rib” of bone across each supraorbital margin.

4) A glabella that is situated at a lower level than the supraorbital margin.

GENUS PARANTHROPUS 95

5) Formation of a central facial hollow associated with a completely flat nasal skele-
ton and a cheek region which is situated anterior to the plane of the piriform aper-
ture.

6) A naso-alveolar clivus which slopes smoothly into the floor of the nasal cavity.

7) Small incisive canals which open into the horizontal surface of the nasal floor.

8) Great enlargement of premolars relative to the molars and canines.

9) Great enlargement of molars and massiveness of tooth-bearing bone.

10) Anterior teeth small when compared to premolars and molars.

11) A tendency for the maxillary canine and incisor sockets to be situated in an al-
most straight line across the front of the palate.

12) Formation on the naso-alveolar clivus of prominent ridges marking the central in-
cisor sockets, but concavities marking the lateral incisor sockets.

13) Cusps of cheek teeth low and bulbous, situated closer to the center of the crown
than in other hominid genera.

14) Formation of flat occlusal wear surfaces on the cheek teeth, accompanied by
smoothly rounded borders between the occlusal surfaces and the sides of the
crowns of the cheek teeth.

15) Virtually completely molarized lower dm1, with anterior fovea centrally situated
and with complete margin.

16) Great increase in the size of the masticatory musculature and attachments, rela-
tive to the size of the skull.

17) Temporal fossa capacious and mediolaterally expanded.

18) Formation of a broad gutter on the superior surface of the posterior root of the zy-
goma.

19) A tendency for the palate to be shallow anteriorly and deep posteriorly.

20) Formation of either a marked pit or a groove across the zygomaticomaxillary su-
ture of the cheek region, at least in the South African Paranthropus.

In view of the well-known and long-standing support for the generic separation
of Paranthropus, it is most surprising to find that Turner & Wood (1993) claimed
that Grine & Martin in 1988 and Wood in 1991 “revived arguments that the robust
taxa deserve allocation to the separate genus Paranthropus.” Turner & Wood did not
mention the numerous works of John Robinson or my supportive writings, in all of
which the name Paranthropus has been alive and well and supported by zoologically
sound credentials. It is certainly welcome news that more human anatomists and
physical anthropologists are coming to the belated realization that Paranthropus
merits generic distinction, but it is to the zoologist John Robinson that credit must be
given for not only recognizing this from the outset, but also for his many clear
explanations of why this was so. Indeed, Robinson commented (1972:3) that his 1954
paper on the subject “is one of the very few in which the morphological evidence is
evaluated at first hand from a taxonomic point of view as opposed to the many that
include statements of opinion about australopithecine nomenclature in the absence
of systematic taxonomic analysis of the relevant evidence.”

Indeed, of all those who chose to lump Paranthropus into Australopithecus, only
two (Tobias 1967; Wolpoff 1974) actually discussed Broom’s and Robinson’s
diagnostic criteria for the genus but concluded that the morphological distinctions
between Paranthropus and Australopithecus did not warrant generic separation.

96 CLARKE

The Several Species of Paranthropus

So what is in a name? Is it, as Mayr (1950) said, “merely a matter of taste” as to
whether one recognizes a second genus, Paranthropus, or 1s itas Dobzhansky (1962)
stated that “the generic category of classification is biologically arbitrary” and that it
is “merely a matter of classificatory convenience how many genera one chooses to
make’?

In the case of Paranthropus, classificatory convenience is not to be lightly
dismissed, but there is a more compelling reason. The generic name which Broom
gave does apply to a very distinct cluster of species of hominids belonging to one
genus and distinguished from the other two genera Australopithecus and Homo by
its dietary specialization. It comprised apparently several species: Paranthropus
robustus from Kromdraai (an early South African form), Paranthropus crassidens
from Swartkrans (a later South African form), Paranthropus boisei (the massive or
hyper-robust East African form), and Paranthropus aethiopicus (the early ancestor
of P. boise’). Whilst all of these species show the main Paranthropus characters or
trends, they differ from each other in a few morphological features and in geographi-
cal or temporal distribution. Homo habilis, Homo rudolfensis, Homo erectus, Homo
ergaster, Homo heidelbergensis, Homo sapiens, and Homo neanderthalensis also
differ from each other morphologically, geographically, or temporally. Just as one
can argue the pros and cons of specific separation among these Homo species (e.g.,
Wood 1992; Stringer 1993), so one can argue the merits of specific separations within
Paranthropus. One fact is, however, very obvious, and that is that Paranthropus 1s
more distinct morphologically from Australopithecus africanus than the latter is from
Homo habilis. \t would be more justified to place 4. africanus into the genus Homo,
as Robinson (1972) has done, than to place Paranthropus into Australopithecus.

There would seem to be two reasons why Robinson’s proposal has not been widely
accepted. The first reason is that 4. africanus as presently constituted includes, in my
view, fossils of an early species of Paranthropus that has led many researchers to
think that 4. africanus has similarities to Paranthropus. | have recently claimed
(Clarke 1988a and b) that the Sterkfontein assemblage actually includes two species,
Australopithecus africanus and a larger-toothed species that has Paranthropus-like
cranial features. It is therefore not surprising that Tobias (1967) should have consid-
ered 4. africanus as it was then constituted to have a range of variation that
incorporated some Paranthropus characteristics and which lent him some support for
his argument that Paranthropus should be classified in the genus Australopithecus.
For example, Sts 71, formerly regarded as an Australopithecus africanus, has the
dished-face, low frontal squama, converging temporal lines, and thin supraorbital
margin of a Paranthropus. That is, in my view, because it is a Paranthropus. It was
specimens such as Sts 71 that had been long accepted as being A. africanus that led
White, Johanson & Kimbel (1981) to write: “From a functional perspective, 4.
africanus crania, mandibles and teeth foreshadow the 4. robustus + A. boisei char-
acter state. Specimens of A. africanus exhibit robust zygomatics, relatively expanded
and anteriorly situated roots of the zygomatic process, tall, vertical mandibular rami,

GENUS PARANTHROPUS 97

and inflated contours of the mandible corpus. They have vertical and well-buttressed
posterior symphyseal regions and enlarged postcanine teeth that wear to flat occlusal
platforms.” They concluded that 4. africanus was already on the robustus clade. With
the much larger sample we now have from Sterkfontein and the growing realization
that “4. africanus” includes two species, the uni-generic view has to be re-examined.
The second reason why Australopithecus has not generally been included in the
genus Homo is that Homo has been considered as a big-brained, cultural hominid so
far removed intellectually from the supposedly less cerebral and uncultural Aus-
tralopithecus that the latter has to be placed in a separate genus. These assumptions
are, however, not necessarily correct. We do not have a sufficiently large sample of
either A. africanus or the earliest Homo habilis crania to be sure that there was no
overlap in cranial capacity. Certainly in cranial morphology Homo habilis is not that
much different from 4. africanus. Thus Clarke (1985) wrote, “The strong similarity
between Homo habilis crania such as O. H. 24 and StW 53 and lightly structured 4.
africanus crania such as Sts 17 and Sts 52 would seem to suggest that 1. habilis could
well have evolved from a population of lightly structured 4. africanus.” Furthermore,
we cannot be sure that 4. africanus was not culturally endowed because, by 2.5 Ma,
stone tools were already in existence at sites in Ethiopia (Harris 1983; Toth & Schick
1986). We do not yet know what species of hominid was responsible for these stone
tools, nor can we be sure that they were the earliest artifacts. The possibility, therefore,
remains open that 4. africanus may yet prove to have been a maker of tools.

The Dietary Adaptation

Even before this new insight concerning the presence of two species from
Sterkfontein Member 4, the differences between an 4. africanus cranium like that of
Sts 5 anda Paranthropus cranium such as SK 48 or SK 46 were so clear-cut, so many
and so profound, that it is extraordinary that those who separated generically the very
similar Sts 5 (A. africanus) and OH 24 (Homo habilis) crania were not prepared to
accept the generic status of Paranthropus. Of course they would argue that Homo
habilis deserves generic separation because of its apparent cerebral and cultural
capacities that do not seem to have been characteristic of Australopithecus. | would
then equally argue that the highly specialized dentition, associated cranial architec-
ture, and massive mandible of Paranthropus speak of a dietary specialization that
separates Paranthropus from the Australopithecus/Homo lineage, as John Robinson
deduced and vigorously maintained in numerous publications from 1954 onward.

In his paper on adaptive radiation in the australopithecines Robinson (1963) noted
that as both Paranthropus and Australopithecus are hominids they have a basic skull
similarity derived from a common ancestor and the fact that they are both bipedal.
Beyond this, he said, the two skulls differ sharply in patterns controlled chiefly by
the specializations of the dentition. He attributed the unusual architecture of the
Paranthropus cranium to its unusual dental specializations. He observed that whilst
Australopithecus and Homo have a balanced pattern of tooth size between the anterior
dentition and cheek teeth, there is an imbalance in Paranthropus with a sudden and

98 CLARKE

disproportionate size increase of cheek teeth compared to anterior dentition. In the
cheek teeth of Paranthropus, Robinson noted “the tooth crowns are large, the enamel
is thick, the occlusal surfaces large and of low relief and the root systems very well
developed. The relatively great and flat occlusal surfaces and the massiveness of the
postcanine teeth clearly point to a prime dietary function of crushing and grinding.
The massiveness of the entire masticatory apparatus and the relatively rapid rate of
wear of the teeth indicate a diet of tough material.” He concluded also from missing
flakes of enamel at the occlusal margins that there was grit in the food, and this
suggested roots and bulbs as part of the diet. He attributed the small size of the anterior
dentition to its lessened importance in the hard vegetarian diet he envisaged. By
contrast, in Australopithecus he said there is far less emphasis on crushing and
grinding, and the larger anterior dentition is consistent with an omnivorous diet.
Furthermore, “the very great similarity in dentition and general skull structure
between Australopithecus and the hominines suggests that they were basically similar
in diet and behaviour” (i.e., omnivores eating both vegetable food and meat).
Paranthropus, however, did not fit the hominine pattern in dentition or skull mor-
phology and, said Robinson, there must be an explanation for such a difference. The
dietary hypothesis seemed, he said, entirely logical and, as far as he was aware, “no
evidence exists which is clearly inconsistent with such an explanation.”

Indeed, microwear studies of Paranthropus and Australopithecus teeth (Grine
1981, 1987) have served to confirm Robinson’s hypothesis of a dietary difference
between the two genera and to confirm also that Paranthropus was eating harder,
tougher, more fibrous foods than was Australopithecus. Grine demonstrated that
Paranthropus molar crowns “display significantly higher incidences of occlusal
pitting, significantly shorter but wider scratches and significantly larger pits than do
Australopithecus teeth.” He also found that the scratches on the Paranthropus molars
showed greater heterogeneity of orientation than those on Australopithecus crowns.
From this he concluded that the diets of Paranthropus and Australopithecus were
qualitatively dissimilar, that the molars of Paranthropus were used for more crushing
and grinding activities than were those of Australopithecus, and that the foods
processed by Paranthropus were substantially harder than those chewed by Aus-
tralopithecus. Such conclusions were supported by the microwear studies on teeth of
living primates by Teaford & Walker (1984) and Teaford (1985, 1986), who were
able from the microwear to distinguish those primates that feed on hard objects from
those that do not. By comparison of microwear features, Grine found that Paran-
thropus grouped with Cercocebus albigena, Cebus apella and Pongo pygmaeus, the
diets of which include hard objects such as date palm seeds and kernels, palm nuts,
and bark. By contrast, Australopithecus grouped with primates that did not eat hard
objects but which concentrated on leaves.

Peters (1981) conducted research into the food plants that could have been utilized
by early African hominids in both wet and dry seasons and experimented with the
range of tooth pressures required to crush and utilize the food sources. He found that
during times of food scarcity when very tough foods such as dry, hard berries had to
be relied upon, large-toothed ape-men, particularly Paranthropus, were at a distinct

GENUS PARANTHROPUS 99

advantage. He also found that low cusped cheek teeth like those of Paranthropus
were better for crushing hard foods than were the higher cusped cheek teeth of Homo,
as such cusps would tend to break. Homo and smaller toothed ape-men would have
either had to use tools to process the food sources or more probably would have eaten
different foods from those of Paranthropus.

Thus as Robinson said, the tooth form and accompanying cranial architecture and
musculature do indicate a dietary difference between the Australopithecus/Homo line
and Paranthropus. One necessary alteration to this theme is that, whereas Robinson
believed Paranthropus existed during wet periods, more recent data indicate that
Paranthropus lived in dry environments (Vrba 1976). This would explain the
adaptation to eating hard, fibrous food such as dry berries, but as Peters (1981)
observes it does not mean that Paranthropus did not eat other foods as well. It rather
means that Paranthropus could utilize foods not accessible to other hominids during
dry conditions.

The most detailed analysis of a Paranthropus cranium and dentition was that of
Tobias (1967) on the well-preserved and almost complete cranium of “Zinjan-
thropus,” Olduvai Hominid 5. Hence his conclusions on the taxonomy of the
australopithecines have had considerable influence on the opinions of his colleagues
concerning the status of Paranthropus. With the 29 years of research and discovery
that have passed since publication of his monograph, it behooves us to look again at
Tobias’s arguments. Although Tobias (1967) argued against the dietary hypothesis
and against generic distinction of Paranthropus, a reading of his arguments shows
that he agreed that “there is a real difference between the two taxa in the disparity
between the sizes of the canines and the cheek teeth,” and he agreed that Paran-
thropus has larger cheek teeth than Australopithecus. Furthermore, he did not
disagree that there are differences in cranial morphology between the two taxa.
However, he attributed six of the cranial distinctions to the enlarged teeth and related
structures and muscles of Paranthropus.

Whilst it is true that enlarged cheek teeth are a characteristic trend of Paran-
thropus, these cannot be considered as the main contributing factor to the unusual
cranial architecture, as we know that even relatively small toothed females of
Paranthropus such as SK 48 or KNM-ER 732 (R. E. F. Leakey et al. 1972) have the
same cranial architecture. This point was discussed at length by Clarke (1977) when
he criticized the use of the colloquial terms “robust australopithecine” for Paran-
thropus and “gracile australopithecine” for 4. africanus. He concluded, “In view of
the confusion which can be caused by the use of the terms ‘gracile australopithecine’
and ‘robust australopithecine,’ the present writer does not use such terms in this thesis
and would advocate that they be dropped from the anthropological vocabulary.”

The unusual cranial architecture of Paranthropus ‘s rather due, as Robinson
observed, to the unusual dental specialization which is manifested by the relatively
enlarged premolars (with molarized lower dm1) and the thick-enameled, low-cusped
flat occlusal surfaces of the cheek teeth. These latter three characters which are crucial
elements in the dietary hypothesis did not feature in Tobias’s argument. Nevertheless,
he concluded that his arguments demonstrated that “With the attenuation and, indeed,

100 CLARKE

collapse of the dietary hypothesis, it would seem that the main prop for the generic
distinctness of the two taxa falls away too” (Tobias 1967:228). On the contrary, it
would seem that the aforementioned case for generic distinction was actually
strengthened by the discovery, and Tobias’s analysis, of Olduvai Hominid 5, by
subsequent discoveries in Tanzania, Ethiopia, and Kenya, and by the research on
microwear by Grine and on food resources by Peters.

The Ancestry of Paranthropus

Both Paranthropus crassidens of Swartkrans and Paranthropus boisei of East
Africa seem to have existed between 1.8 and | million years ago; Paranthropus
robustus of Kromdraai may be a little older than this (Vrba 1982; Vrba & Panagos
1982). It had been generally assumed, especially by those who classify them as
Australopithecus, that they evolved out of 4. africanus which dates to around 2.5 to
3.0 million years ago from Sterkfontein, Taung, and Makapansgat. Robinson (1963,
1972), however, did not accept this concept but believed conversely that 4. africanus
evolved out of an early form of Paranthropus that had large anterior teeth. In this
belief he was in one respect remarkably prophetic because there are now newly
discovered fossils which indicate that an ancestral Paranthropus with large anterior
teeth existed in East Africa 2.5 million years ago. However, his belief that 4. africanus
evolved out of such an ancestor does not seem to fit with the fossil data we now have
in the form of 3 to4 million year old Australopithecus afarensis that, with its relatively
small cheek teeth, seems a more plausible ancestor to 4. africanus.

From West Lake Turkana in Kenya has been discovered a 2.5 million year old
cranium of a hominid (WT 17000) that has all the hallmarks of Paranthropus boisei,
but with a more prognathic muzzle and larger canines and incisors (Leakey & Walker
1988). From Sterkfontein, Clarke (1988a and b) has recognized the existence of a
second species of hominid alongside 4. africanus at a date of between 2.5 and 3.0
million years ago. This second species, exemplified by StW 252, also has Paran-
thropus features in its thin supraorbital margin, sagittally converging temporal lines
enclosing a slight supraglabellar hollow, broad interorbital distance, flat face, large
molars and premolars. Yet, unlike Paranthropus, it has large canines and incisors
indicating that it still retains these ancestral pongid-like features whilst specializing
in its enlarged cheek teeth. This would be expected in an early form of Paranthropus
because it is temporally nearer to a common hominid ancestor. First would come the
dietary specialization with enlargement of cheek teeth. Only when the large, project-
ing canines and incisors became both unnecessary and a hindrance to side-to-side
grinding would they become reduced in size and prominence.

Conclusions

Robinson (1972) devoted considerable discussion to the concept of the genus,
stating that “a genus represents a clearly defined adaptive zone or way of life, within
which various species can occur that represent no more than variations in detail on
the basic adaptive theme.” In support of this concept, he quoted a definition by

GENUS PARANTHROPUS 101

taxonomists Mayr, Linsley & Usinger (1953) which is worth repeating here: “The
genus, as seen by the evolutionist, is a group of species that has descended from a
common ancestor. It is a phylogenetic unit... . The genus, however, has a deeper
significance. Upon closer examination, it is usually found that all the species of a
genus occupy a more or less well-defined ecological niche. The genus is thus a group
of species adapted for a particular way of life... . On this theoretical basis, it is
probable that all generic characters are either adaptive or correlated with adaptive
characters.”

It is clear that the fossils assigned to the genus Paranthropus do fit the above
definition in that they belong to a cluster of hominid species that were united in their
dietary specialization, in which they had evolved relatively large, low cusped and
smooth margined cheek teeth designed to crush and grind hard foods, especially in
dry environments. The unusual cranial architecture evolved at the same time to
maximize the force applied through the cheek teeth in both vertical (crushing) and
lateral (grinding) movements. The earliest known species of Paranthropus, found in
East Africa, lived 2.5 million years ago and still retained large incisors and canines
that were to become greatly reduced by about 2 million years ago.

There were different species of Paranthropus living in East and South Africa at
the same time as the smaller-toothed Australopithecus/Homo lineage. There was thus
a similar situation to that within the Carnivora, where both the East African and South
African species of the genus Hyaena occupy the same areas as the genus Crocuta.
The cranial and dental anatomy of Hyaena and Crocuta resemble each other to a
greater degree than do those of Paranthropus and Australopithecus, and yet there is
no doubt that Hyaena and Crocuta belong to distinct genera.

Clarke (1977) noted a parallel situation to that of Australopithecus and Paran-
thropus which can be seen among the primates of the grade Strepsirhini: “There are
great similarities between the skulls of Galago and Perodicticus or Galago and
Arctocebus (Hill 1953) but they have totally different skeletal anatomy. They all
belong to the Family Lorisidae, but Perodicticus and Arctocebus are slow climbers,
of the Subfamily Lorisinae whilst Galago is a vertical clinger and leaper of the
Subfamily Galaginae (Napier & Napier 1967). Although Perodicticus and Arctoce-
bus have similar skulls, skeleton and locomotor pattern, there are slight differences
in their anatomy and behavior which have been considered sufficient to separate them
at the generic level.”

Thus the name Paranthropus, meaning “parallel to man,” refers to a very impor-
tant, well-adapted and unusual primate that existed for a period of at least one and a
half million years alongside our own ancestral lineage.

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Origin and Evolution of
the Genus Homo

Bernard Wood

Hominid Palaeontology Research Unit
Department of Human Anatomy and Cell Biology
The University of Liverpool

PO Box 147

Liverpool L69 3BX , UK

A subset of hominid fossils recovered from East African sites, and dating to 1.5
Ma or earlier, has been assigned to the genus Homo. Three species are identified
within this material, herein called “early Homo.” One species resembles Homo
erectus and is either interpreted as “early African” H. erectus, or Homo ergaster.
Its incorporation within the genus Homo is well justified and widely supported by
evidence from both phenetic and cladistic studies. The two other species, Homo
rudolfensis and Homo habilis, are taxonomically more ambiguous. Homo rudolfen-
sis has an absolute and relative brain size comparable to H. ergaster, but is only
indirectly associated with postcranial remains that are evidently from a biped. Its
masticatory anatomy is reminiscent of the australopithecines. The cranial base of
Homo habilis is relatively foreshortened and wider than that of australopithecine
crania, trends that are continued in later Homo. However, its absolute brain size
is modest and its postcranial skeleton is australopithecine-like. If obligatory
bipedalism is a Homo prerequisite, then H. habilis should not be included in that
genus. The relationship between 4. africanus and Homo is not clear. Cladistic
analyses based on craniodental characters narrowly favor it being the sister group
of Homo and thus strengthen claims for its inclusion in that genus. However, there
is an equally compelling case to regard early African Homo erectus as the ancestral
species of Homo, and thus to restrict the definition of the genus. The period between
2.5 and 1.5 Ma saw the emergence of an unambiguous Homo lineage. However, the
combinations of characters within H. rudolfensis and H. habilis suggest that it was
possible to acquire some of the characteristics of Homo and not others. We have
yet to understand the context within which these various evolutionary initiatives
were played out.

There is a widely-held but probably unrealistic expectation that the boundaries of
the genus Homo will prove to be well-defined. This expectation ignores the reality
which is that genera are “necessarily more arbitrary” than species (Simpson 1961).
This proposition is borne out by most of the diagnoses of Homo which have been
offered from time to time. These usually contain a summary of the features of the
species which the authors judge should be subsumed within Homo as well as

Contemporary Issues in Human Evolution Memoir 21, Copynght © 1996
Editors, W.E. Meikle, F.C. Howell, & N.G. Jablonski California Academy of Sciences

106 WOOD

references to morphological trends such as an enlarged brain, reduced dentition, etc.,
which the species are judged to share.

For many years the only fossil evidence which helped to bridge the substantial
divide between the morphology of modern humans, on the one hand, and that of the
living African apes, on the other, was attributed to Homo erectus. Dentally and
postcranially, its affinities with living Homo sapiens were evident, despite its low
and heavily buttressed cranium with an average absolute brain size substantially
smaller than that of modern human populations.

The discovery, in 1924 and thereafter, of fossils which are now usually assigned
to Australopithecus, or to Australopithecus and Paranthropus (see Wood (1991) and
Grine (1993) for up-to-date reviews of this material) provided evidence of creatures
which were more ape-like than H. erectus. Compared to living apes, australopithe-
cines demonstrate only a modest degree of brain enlargement, and while they
evidently placed more emphasis on bipedal posture and locomotion than living apes,
their postcranial skeletons still retain many features linked with climbing. Their
anterior dentition was reduced and their muzzles were foreshortened compared to the
living apes, but the postcanine teeth of the australopithecines are large relative to
those of the living apes. Contemporary commentators were unwilling to amend their
diagnosis of Homo to allow for the inclusion of the new fossils within that genus (but
see Mayr (1950) and Robinson (1972) for contrary views) and instead chose the genus
names Australopithecus (meaning “southern ape”) and Paranthropus (meaning
“beside man”) which served to emphasize the ape-like features of the new material.

In the last three decades, fossils have been discovered which helped to close the
remaining morphological gap between the australopithecines and H. erectus. These
remains, attributed formally or informally to H. habilis, are a morphological palimp-
sest. Whereas their brains and teeth were intermediate between the australopithecines
and H. erectus, postcranially they were judged to be decidedly Homo-like.

The taxonomic options for this new material were either to relax the diagnosis of
Homo to allow the inclusion of a species-group with more ape-like features than /.
erectus, or to broaden the diagnosis of Australopithecus or Paranthropus to allow the
inclusion of creatures with more Homo-like features such as obligatory bipedalism
and a reduced dentition.

This paper briefly reviews the fossil evidence for what is now often called “early
Homo” and sets out options for its taxonomic interpretation. It then explores the
relationships between the component species, examines the grounds for including
each of them within Homo, summarizes the case for Homo monophyly, and then
surveys the hominid fossil record for likely ancestors of the genus. Finally, the various
early Homo taxa are scrutinized for evidence about their evolutionary grade. Do they
all belong to the same locomotor and dietary grade, or is there evidence of any grade
shift within the material subsumed within early Homo?

Fossil Evidence

This paper interprets “early” to include fossils which are dated to 1.5 Ma, or before.

EARLY HOMO 107

This effectively restricts the sample to Africa, for very few hominid sites in Asia can
be dated with any reliability to much beyond 1 Ma (Swisher et a/. 1994; Huang e7 al.
1995). The majority of the African fossil evidence for early Homo comes from East
Africa, with Olduvai Gorge and sites in the Omo Group, notably Koobi Fora,
contributing most of the sample. Specimens from Sterkfontein (e.g., Stw 53) and
Swartkrans (e.g., SK 847) also belong in the early Homo category, but they will not
be referred to in detail in this discussion; the affinities of the latter have recently been
reviewed (Grine ef a/. 1993).

Details of the early Homo hypodigm have been presented elsewhere (Wood 1991,
1992); the better preserved specimens are listed in Table |. The material can be
divided into two main morphological categories. Some of the remains share features
with Asian H. erectus and have been referred to in the literature as H. erectus (Brown
etal. 1985), early African H. erectus (Bilsborough 1992), or as Homo ergaster (Wood
1992). These remains range in age between 1.5 and 1.9 Ma, with most of the sample
coming from the younger end of the range. The differences which distinguish them
from the remainder of the early Homo sample include increases in the overall length
of the cranium, the breadth of the cranial vault, and the width of the nasal aperture,
reductions in the length of the cranial base and the width of the postcanine teeth, and
a posterior attenuation of the molar tooth row (Wood 1991:277).

TABLE |. Examples of the Remains Attributed to Early Homo Listed by Site.

Koobi Fora Olduvai West Turkana

(KNM-ER) (OH) Omo (KNM-WT)
Skulls and crania 730, 1470, 1590, 7, 13, 16, 24, 62 L894-1 15000

1805, 1808, 1813,

3735,3883
Mandibles 730, 820, 992, 37, 62 Omo 222-2744 —-
1482, 1802, 3734
Associated teeth 808, 1814 39 — 5496
Postecranial 730, 1472, 1481, 7, 8, 35, 62 -- 15000

1808, 3228, 3735

The second of the two main morphological categories includes specimens which
have been assigned, or likened, to H. habilis. The original hypodigm of . habilis
was identified among remains recovered from Beds I and I] at Olduvai Gorge (Leakey
et al. 1964). Since then the hypodigm has been expanded to include other hominid
remains from Beds I and II at Olduvai and a substantial sample recovered from the
Koobi Fora and Shungura Formations, now known to be components of a larger
regional complex of fossiliferous sediments referred to as the Omo Group (Feibel ef
al. 1989). The H. habilis category subsumes a substantial range of size and shape
variation which has been the subject of different interpretations. Tobias (1991) and
Miller (1991), the former on the basis of a wide range of features and the latter on
cranial capacity alone, assess this variability to be compatible with an attribution to
a single species. Wood (1985), Stringer (1986), Chamberlain (1989), Rightmire

108 WOOD

(1993), Kramer ef al. (1995), and Grine et a/. (1996) judge the extent and nature of
the variation to be less easily accommodated within one species and have proposed
that the remains should be attributed to not one, but two species. Stringer (1986)
divides the sample temporally, Chamberlain (1989) geographically, and Rightmire
(1993) phenetically. Wood (1991, 1992) concurs with Chamberlain’s judgement that
the Olduvai hypodigm of H. habilis is not excessively variable, but does find evidence
of excessive variability in the Koobi Fora sample. In Wood’s scheme two taxa are
recognized at Koobi Fora, one (H. habilis) which is also sampled at Olduvai, and the
other (Homo rudolfensis Alexeev, 1986) which is not. The taxonomic separation
Wood proposes was based on the cranial remains, as are all the others cited above,
and the cardinal features distinguishing the two taxa are summarized in Table 2.

Why Homo?

If we accept the taxonomic interpretation of early Homo referred to above, (a
subdivision into three species: H. ergaster, H. habilis, and H. rudolfensis), what are
the grounds for including these species taxa within the genus Homo?

Several morphological trends set H. erectus and H. sapiens apart from the various
species of australopithecine, but five are particularly evident. Firstly, the two species
have a larger body size than australopithecine species. Secondly, the brain sizes of
fossils assigned to the two species are both absolutely and relatively larger than those
of the australopithecines. Thirdly, when compared with australopithecines, for both
H. sapiens and H. erectus there is clear evidence of a reduction in emphasis on the
postcanine teeth. This is reflected in both absolute and relative premolar and molar
tooth size reduction and in the posterior attenuation of the molar tooth row, so that
the third molars, which in the australopithecines are the largest teeth in the molar row,
reduce in size so much that in modern humans they are the smallest. Fourthly, there
is a shift in locomotor mode such that later Homo species are obligatory and not
facultative bipeds (Prost 1980). Fifthly and finally, it is one of the characteristics of
Homo that somatic growth and development are retarded relative to the apes, resulting
in the birth of infants which are secondarily altricial.

To what extent do the three early Homo taxa conform with these trends? Turning
first to H. ergaster, there is little doubt that the remains attributed to this taxon provide
compelling evidence that, relative to australopithecines, this species demonstrates
increases in body and brain size, a reduction in absolute and relative postcanine tooth
size, and posterior attenuation of the molar row. Evidence about the rate of maturation
in this species is confusing, but observations on the mandible KNM-ER 820 suggest
that at least one individual in this group demonstrates a pattern of dental development
not unlike that of australopithecines and quite unlike that of later Homo species.

The features of the Homo habilis sample provide a much more ambiguous message
about its taxonomic affinities. If, as seems likely, OH 62 and KNM-ER 3735 prove
to be conspecific, then deductions based on these two partial skeletons suggest that
H. habilis was a creature whose body weight and stature were well within the range
of the temporally earlier and morphologically more primitive australopithecine

EARLY HOMO

109

TABLE 2. Major Differences Between Homo habilis and Homo rudolfensis

Homo habilis Homo rudolfensis
Absolute brain size X= 610 ce X= 751 cc
Relative brain size EQ approx. 4 EQ approx. 4
Overall cranial vault morphology Enlarged occipital sagittal Primitive

Endocranial morphology
Suture pattern

Frontal bone

Parietal bone

Face - overall

Nose

Malar surface
Palate
Upper teeth

Mandibular fossa
Foramen magnum
Mandibular corpus

Lower teeth

Limb proportions
Forelimb robusticity
Hand

Hindfoot
Femur

contribution

Primitive sulcal pattern
Complex

Incipient supraorbital torus
Coronal > sagittal chord
Upper face > midface breadth

Margins sharp, everted; evident
nasal sill

Vertical or near vertical

Foreshortened

Probably two-rooted premolars

Relatively deep

Orientation variable

Moderate relief on external
surface

Rounded base

Buccolingually-narrowed
postcanine crowns

M3 reduction

Reduced talonid on P4

Mostly single-rooted

Ape-like

Mosaic of ape-like and modern
human-like features

Retains climbing adaptations
Australopithecine-like

Frontal lobe asymmetry

Simple

Torus absent

Primitive

Midface > upper face breadth;
markedly orthognathic

Less marginal eversion; no nasal
sill

Anteriorly inclined

Large

Premolars three-rooted; absolute-
ly and relatively large anterior
teeth

Shallow

Anteriorly inclined

Marked relief on external surface

Everted base
Broad postcanine crowns

No M3 reduction
Relatively large P4 talonid
Twin, plate-like, P4 roots, and 2T,
or even twin, plate-like P3 roots
?
?
2

species. In terms of absolute and relative brain size, H. habilis does show an advance
with respect to australopithecines. Postcanine tooth area is absolutely small in H.
habilis, but when scaled by estimated body weight the relative size of premolar and
molar crowns is little different than in the so-called “gracile” australopithecine
species (Wood 1995). Postcranially the skeleton of OH 62 is primitive with respect
to the size and proportion of the skeleton when compared with the later Homo species.
There is some evidence about the rate and pattern of H. habilis development which
suggest that it is like the pattern observed in the australopithecines (Dean in press).

The initial inclusion of H. habilis within Homo was heavily dependent upon

110 WOOD

interpretations of the OH 8 foot which suggested that it belonged to a hominid with
“an upright stance and a fully bipedal gait” (Day & Napier 1964:970). Given that
more recent studies have drawn attention to the mosaic nature of the OH 8 foot, with
the morphological correlates of prehensility being combined with features linked to
bipedalism, do any of the cranial and dental differences between this species and
Australopithecus still justify its inclusion in Homo? The shape and proportions of the
cranium and the detailed morphology of the teeth provide the clearest case for
separating H. habilis from the australopithecines. Although little different in brain
capacity, the neurocranium and face of H. habilis are proportioned much more like
that of later Homo crania. The cranial base 1s also absolutely and relatively shorter,
the foramen magnum more centrally-placed and horizontally-inclined, and the oc-
cipital bone makes a greater contribution to the sagittal arc length. The midface is no
longer the broadest of the three facial components, and the postcanine teeth are
relatively narrow buccolingually. The ontogenetic basis and the functional signifi-
cance of the differences between H. habilis and the australopithecines are ill-under-
stood, but they do suggest that the structure of the cranium of H. habilis was beginning
to be reorganized along the lines of later Homo.

There is, as yet, no well-preserved or even partial skeleton of Homo rudolfensis,
so its limb anatomy can only be inferred from contemporary, but indirectly associated,
postcranial remains. Body weight estimates based on orbital dimensions suggest that
the body mass of H. rudolfensis was on the order of 40-65 kg (Aiello & Wood 1994).
The absolute brain size estimates for H. rudolfensis are large, but in terms of relative
brain size it is comparable to that of H. habilis. The locomotor anatomy of H.
rudolfensis, as inferred from unassociated specimens such as the femora KNM-ER
1471 and 1482, suggests that it was probably an obligatory biped.

It is the cranial and dental anatomy of H. rudolfensis which is closest to that of the
known australopithecine taxa. The cranium of H. rudolfensis is apparently well-pneu-
matized and its greatest width is across the mastoid region of the temporal bone. The
midface is broad, the malar region deep, the face orthognathic, the crowns and roots
of the premolar teeth complex, the molars relatively large, and the enamel of the
postcanine teeth is relatively thick. All these features point to 1. rudolfensis retaining
a masticatory system that is more australopithecine-like than Homo-like.

Is the Genus Homo a Monophyletic Group?

A monophyletic group comprises “an ancestral species and all of its descendants”
(Wiley er al. 1991). Do the species that have been identified as belonging to Homo
make up what Wiley and his colleagues also call “a unit of evolutionary history”?
Very few hominid taxonomic schemes in the contemporary literature identify an
ancestral species for the Homo clade. In the few that do, 4. africanus is usually cast
in the role of ancestor. However, cladograms which place 4. africanus as the stem
species of Homo are only narrowly more parsimonious than schemes which link 4.
africanus with the Paranthropus clade (Wood 1991). Others cite A. africanus, or a
creature very like it, as the common ancestor of a clade incorporating both Homo and

EARLY HOMO DN

Australopithecus (or Paranthropus) boisei and robustus (Skelton & McHenry 1992).
If further research supports the claims that 4. africanus is the exclusive ancestral
species for the Homo monophyletic group, then the earlier suggestion (Robinson
1965) that 4. africanus should be abandoned in favor of H. africanus should be
considered.

The results of cladistic analyses based on cranial, dental, and mandibular charac-
ters emphasize the similarities between the H. rudolfensis subset of early Homo and
Paranthropus (Wood 1991). Indeed, it is only marginally less parsimonious for H.
rudolfensis to be the sister taxon of Paranthropus than H. habilis. However, masti-
catory morphology is among the less reliable indicators of evolutionary relationships
for, even in its finer detail, it is prone to homoplasy in a range of African large
mammals (Turner & Wood 1993). Of the two options, the one that regards the
“rudolfensis” hypodigm as a gnathically-modified, larger-brained, bipedal species of
Paranthropus is more exotic than the second interpretation, which is that the Paran-
thropus-like morphology of H. rudolfensis is either a reflection of the closeness of
the relationship between Homo and Paranthropus (i.e., the morphological complex
represents a set of retained ancestral characters; see Skelton & McHenry 1992) or
that it reflects similar adaptive responses within the Paranthropus and Homo clades
to external, probably climatic, factors which, in turn, affected the nature of the food
available to the hominids (i.e., the morphological complex is homoplasic).

Early Homo — One or More Evolutionary Grades?

The three species which are presently subsumed in the informal category early
Homo represent a wide adaptive range. Early African H. erectus, or H. ergaster, 1s
the only one of the three species in which overall body size and shape, absolute brain
size, masticatory anatomy, and posture and locomotion are all unambiguously
tending towards the highly derived conditions we see in later Homo species. In many
ways early African erectus would make a credible ancestral species for a genus
restricted to H. erectus, Homo neanderthalensis, any other species taxa recognized
within Middle Pleistocene Homo, and H. sapiens. In constrast, H. rudolfensis retains
an australopithecine-grade masticatory system and H. habilis an australopithecine-
grade physiognomy and locomotor system. The grounds for their inclusion in Homo
are a good deal more tenuous than those for including early African H. erectus.

On the present evidence there are grounds for reconsidering the boundaries of the
genus Homo and setting them to include the monophyletic group comprising early
African H. erectus (H. ergaster) as the ancestral species and H. erectus, H. sapiens,
and whatever other species taxa should be used to classify Homo from the Middle
Pleistocene as the remainder.

112 WOOD

Conclusions

The considerations discussed above serve to remind us that the fossil record is
relatively mute about the events which resulted in the emergence of Homo. We are
aware from the more recent fossil record of the major morphological “components”
of Homo, but we remain ignorant about their functional interrelationships, the order
in which they arose, and their relationships to the environmental and ecological
pressures and constraints prevailing around 2 Ma. Of the approaches presently being
explored to remedy this ignorance, the pursuit of the constraints imposed by the need
to balance heat, water, and energy budgets (Wheeler 1984, 1985, 1991a and b, 1992a
and b, 1993; Ruff 1991) and studies of the evolutionary history of contemporary
large-bodied mammals (e.g., Bishop 1994) hold out the greatest promise.

Acknowledgements

Research incorporated in this paper was supported by grants provided by The
Leverhulme Trust and the Science-based Archaeology Committee of the SERC.

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114 WOOD

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Current Issues in Modern
Human Origins

Christopher B. Stringer
Department of Palaeontology
The Natural History Museum

Cromwell Road
London SW7 5BD, UK

The study of modern human origins is marked by fundamental disagreements
about the best methods for recognizing and analyzing the variation among fossil
samples. Distinguishing intraspecific from interspecific variation is crucial for
classifying Pleistocene Homo. Four recent proposals relevant to understanding
modern human origins are discussed: that recognition of only three species of the
genus Homo underestimates the true number of species; that Homo erectus should
be sunk into Homo sapiens; that all Middle Paleolithic human fossils from the
Levant represent variants of a single population; that the Skhul-Qafzeh samples
are highly variable and have been mischaracterized as "modern." The most
reasonable division of middle and later Pleistocene Homo is into at least four
species: H. erectus, H. neanderthalensis, H. sapiens, and a common ancestor to H.
sapiens and H. neanderthalensis. This fourth species may be referred to as H.
heidelbergensis, H. rhodesiensis, or H. helmei, depending on its precise composition.

The recent ferment in the study of modern human origins has led to an unprece-
dented burst of scientific activity in the form of fieldwork and research, in debate,
both in the scientific and popular media, and in a reexamination of fundamentals in
the subject. In this paper I intend to look critically at three basic issues and discuss
some recent proposals concerning research in modern human origins. The first two
issues are absolutely fundamental in that they concern the way we group and study
the fossil material. The most widely used taxonomy of the genus Homo recognizes
the existence of three species, Homo habilis, Homo erectus, and Homo sapiens. Homo
habilis was restricted to Africa and was apparently extinct by 1.5 Ma. The taxon
Homo erectus is known from Africa and Asia and usually includes African forms
dating prior to one million years (for example Olduvai Hominid 9 and the Koobi Fora
KNM-ER 3733 specimen). Homo sapiens is usually informally divided into an
“archaic” subdivision, including most African and European Middle Pleistocene
fossils as well as the Late Pleistocene Neanderthals, and an ‘anatomically modern”

Contemporary Issues in Human Evolution Memoir 21, Copynght © 1996
Editors, W.E. Meikle, F.C. Howell, & N.G. Jablonski California Academy of Sciences

116 STRINGER

subdivision comprising forms such as those from Skhul, Qafzeh, and the European
Upper Paleolithic, as well as recent human samples.

Proposal 1: Recognition of only three species of the genus Homo
underestimates the true number of species

Tattersall (1986, 1992) has commented that living primate species numbers would
be seriously underestimated if we had to rely on only the skeletal parts which might
be preserved as fossils. He has therefore suggested that species numbers in fossil
hominids are probably underestimated, and that the Neanderthals should be distin-
guished as a separate species, with the likely addition of several more species
requiring recognition in the Early and Middle Pleistocene.

As we examine and interpret the fossil record to reconstruct phylogenies, we
require a reasonable basis for species recognition which will allow a clear demarca-
tion between intraspecific and interspecific variation. Otherwise, there is the likeli-
hood that significant taxonomic distinctions will be trivialized as intraspecific
polymorphisms, leading to a failure to recognize significant speciation events, or
conversely, that relatively trivial intraspecific differences will be elevated to a level
of fundamental significance. The best known species concept is that of the “Biologi-
cal Species,” which refers to the presence of a common gene pool. This concept is
necessarily only of direct applicability to the living biota, but many workers have
attempted to use skeletal variation present within living species as a yardstick by
which to judge past specific variation. However, there are immediate problems here
for the hominid fossil record when we consider whether to use only present-day
human variation as a guideline or to extend comparisons to include other primates.
As we have seen from Proposal 1, features which separate known, distinct living
primates species may be difficult or impossible to find in the skeleton. Another
species concept which is difficult to employ in the fossil record, whatever its
theoretical validity, is the “Recognition Concept.” This argues that the primary cause
of speciation is not the separation of once common gene pools by isolation, but a
divergence in the once shared Specific Mate Recognition System (SMRS) within a
species. The SMRS can range from a biochemical signal, such as a particular
pheromone, to an elaborate morphological display, such as the shape of antlers
common to the males of a particular species of deer. A change in the SMRS in some
members of the species can produce an immediate behavioral or even physical barrier
to fertilization with other members of the species. According to the Recognition
Concept, most of the morphological features which we can observe as separating
related species have developed independently of rifts in previously shared fertiliza-
tion systems.

Because of the inherent difficulties in relating species concepts based on living
species to the fossil record, other workers have preferred to employ concepts based
on the presence of synapomorphies (shared derived characters). For those who are
prepared to go further than what has been termed “transformed cladistics” or “natural

order systematics,” the presence of such shared characters form the basis of a

MODERN HUMAN ORIGINS 117

“Phylogenetic Species Concept,” which arises from the evolutionary process: a
species is the basal group of organisms within which there is a parental pattern of
ancestry and descent. Some workers have favored the use of autapomorphies in
species recognition (for example Tattersall 1986). Others are prepared to use combi-
nations of apomorphies and plesiomorphies as long as the combination is unique to
the species concerned. A related, but not necessarily cladistically based, concept is
that of the “Evolutionary Species,” where branching points determine species recog-
nition, and the unique evolutionary role of a species is the basis of its recognition. In
an important volume (Kimbel & Martin 1993), the use of these various species
concepts is reviewed, and further proposals regarding species recognition are made.
In their contribution to the Kimbel & Martin volume, Kimbel & Rak (1993) support
the use of the Phylogenetic Species Concept and make the point that it does not have
to be based on autapomorphies alone. A species can be recognized by any unique set
of character states, and prior knowledge of the cladistic status of the characters and
the species is not required — it only needs to be diagnosable in space and time.
Harrison (1993) goes even further in his discussion of cladistics and the species
problem. Although a confirmed cladist, Harrison argues that species diagnosis need
have no cladistic basis — it is merely a phenetically determined distinctive morpho-
type. A combination definition of characters which may be known to be, or may turn
out to be, apomorphies or plesiomorphies provides a practical approach to species
recognition, and a differential diagnosis (distinguishing species individually from
other species) is preferable to a single universal diagnosis.

Tattersall (this volume; see also Tattersall 1992) has also moved away from his
earlier emphasis on autapomorphies to a position where apomorphies are employed
as part of “morph” recognition. Given the lack of morphological differentiation
between many closely related primate species, Tattersall argues that if discrete
morphs (minimum diagnosable units) can be recognized in fossil assemblages, these
probably do represent distinct species. This practical, rather than theoretical, proposal
is one I also favor for species recognition in the fossil record. Tattersall argues that
good diagnosable characters for (anatomically modern) Homo sapiens, Homo nean-
derthalensis, and Homo heidelbergensis exist, amongst the forms generally recog-
nized as Homo sapiens (sensu lato), and that these should all be recognized
specifically. However, he also claims that no reasonable list of shared characters has
ever been produced for Homo sapiens (s.1.). In fact I did produce one (Stringer 1984)
as part of a discussion of the status of the species Homo erectus (Table 1), and
although I no longer consider this list appropriate for a species diagnosis, I will return
to it later.

Proposal 2: Homo erectus should be sunk into Homo sapiens

A contrasting proposal which has been revived recently in conjunction with
discussion of the multiregional model of modern human origins is that the species
Homo erectus should be sunk into Homo sapiens (Wolpoff et al. 1994), with Homo
sapiens originating ina late Pliocene cladogenetic event. This sinking of the species

118 STRINGER

TABLE I. Possible synapomorphies of Homo sapiens (sensu lato)
(vs. H. erectus), modified from Stringer (1984)

. More gracile tympanic

. Greater midface projection

. Laterally retracted supraorbital torus
Longer, more curved parietals

Higher, more curved temporal squama
. Lengthened occipital plane

. Larger endocranial volume

. Reduced total facial prognathism

. Parallel-sided or expanded parietal arch
10. Reduced cranial cortical bone

11. Reduced occipital torus

12. Laterally reduced supraorbital torus
13. No iliae pillar

wee

bh Ue

OOD

Homo erectus 1s justified by the claim for genetic continuity between Early and Late
Pleistocene human populations in the various regions of the Old World, for example
between Neanderthals and modern humans in Western Eurasia; between populations
represented by the Early Pleistocene Lantian and Middle Pleistocene Zhoukoudian
fossil samples and recent oriental and native American populations; and between the
Indonesian samples known from sites such as Sangiran and Ngandong, and native
Australian populations.

Wolpoff et al. (1994) argue that Homo sapiens can be viewed as a single
evolutionary species spanning the entire Pleistocene. “Evolutionary tendencies” are
linked to the evolving cultural system and geological criteria are proposed for early,
middle, and late sapiens categories, apparently correlated to the Early, Middle, and
Late Pleistocene. If the multiregional model of modern human origins is actually
representative of the course of human evolution over the last million years or so, then
there is no doubt that only one species of human should be recognized (Homo
sapiens). However, the Wolpoff ef al. proposal to sink Homo erectus 1s, like all
species assignments and phylogenies employing fossils, an hypothesis about what
really happened in the past. As such it should be testable, although the authors have
provided little or no basis for testing. Instead it 1s assumed that the relationships are
there and merely need to be supported by data collection (Stringer & Brauer 1994).
Certainly the validity of the proposed cladogenetic origin of Homo sapiens (sensu
lato) can be tested to see whether it corresponds to an identifiable speciation event,
and most workers would agree that there is good evidence for cladogenesis with the
origin of Homo erectus (sensu lato) (or Homo ergaster of Wood 1992), which would
then mark the origin of the Homo sapiens (sensu lato) clade of Wolpoft et al. (1994).

However, their proposal that the polytypism of present day Homo sapiens is
comparable with, and an extension of, the polytypism of their Homo sapiens evolu-
tionary species throughout the Pleistocene seems difficult to accept. Unfortunately
we lack large, contemporaneous samples for Pleistocene hominids (with the probable
exception of Atapuerca, discussed below). However, we do have good data on

MODERN HUMAN ORIGINS 119

modern morphological polytypism. Table 2a presents data for cranial samples of four
regionally distinct recent groups with an additional contrast provided by sexual
dimorphism. The measurements are those of basion-nasion length (BNL), midline
nasal height (NLH), midline projection of the lower nasal margin (SSS), frontal
doming (FRS), parietal doming (PAS), and position of midline maximum occipital
projection (OCF). For comparison, the means for five later Pleistocene cranial
samples (which would all be included in Wolpoff ef a/.’s (1994) “late sapiens”
category) are provided. The mean data show considerable variation, but much of this
is size related. If we standardize for size by log transformation and row stand-
ardization (Corruccini 1987), we are left with a more realistic picture of shape
differences among the recent cranial samples, and these are actually very small indeed
(Table 2b). By contrast, the transformed data for the fossil samples show greater
variation, indicating that the distinctions among the fossil groups are of a different
order from those among the recent samples —a point which has been made many
times before (e.g., Howells 1989; Stringer 1974; van Vark & Bilsborough 1991). Of
course, the fossil samples probably span something like 100,000 years, while the
recent samples (although covering a greater geographical range) are penecontempo-
raneous, yet we can immediately reduce the between-sample differences in the fossils
by regrouping the data as shown in Table 2c. Here the division corresponds to what
I would regard as modern vs. non-modern, and the time span of the “modern” samples
is now comparable with the much more varied fossil samples of Table 2 — about
100,000 years. Even now, despite the reduction of the archaic among-sample differ-
ences, the metrical differences are still more marked in the archaic than the more
widely-based “modern” grouping.

Thus, there appears to be little or no justification for the view that modern variation
is equivalent to variation at earlier time levels in the Pleistocene. Another argument
used to support the merging of Homo erectus and Homo sapiens is the claim for
continuity of characters between the two species in the same regions. The recent
proponents of regional continuity have never used global skeletal samples to provide
data in support of their ideas, and an examination of such data gives poor support for
regional continuity (see for example Howells 1973, 1989; Corruccini 1992; Groves
1989; Stringer 1992a and b; Lahr 1994). The fundamental mechanism for the
maintenance of relatively minor regional characters over a period of one million years
or so in the face of major evolutionary changes in the cranium (not to mention major
and repeated climatic changes) is also unclear. While drift and selection were
formerly proposed as local mechanisms of maintenance (Wolpoff ef al. 1984;
Wolpoff 1989) the role of selection is now being played down (Thorne & Wolpoff
1992), leaving an explanatory void.

The primary test of regional continuity is to establish whether it operates in the
Late Pleistocene. If it does not operate during the last stages of human evolution, then
the regional sequences are broken, however convincing they look at an earlier date
in areas such as Europe and Indonesia, where most workers do recognize regional
continuity in the Middle Pleistocene. Because early modern fossils in Europe, Asia,
and Africa do not closely resemble their modern counterparts phenetically or in

120 STRINGER

TABLE 2. “Modern” vs. “Archaic” cranial data comparisons
NORSEM, DOGONF, AUSM and JAPF are respective male (M) or female (F) means of the
Howells samples from Norway, West Africa, Australia, and Japan. EUNEAM and ASNEAM
are means of late Neanderthal samples from Europe and Asia, AFLARCH is the African late
archaic mean, SQMEAN is Skhul-Qafzeh and EUPMEAN early Upper Paleolithic mean.

BNL NLH SSS FRS PAS OCF
2a. RAW DATA (mm)
NORSEM 101.80 51.96 22.96 25.11 24.69 47.40
DOGONF 94.87 46.17 21.04 25.67 22.25 44.38
AUSM 101.98 49.69 24.13 25.23 23.90 43.52
JAPF 95.63 49.37 21.73 25359 23.49 46.83
EUNEAM 113.50 60.64 38.00 20.72 17.56 39:15
ASNEAM 116.40 64.93 38.00 19.07 21.97 45.40
AFLARCH 105.33 47.25 29.50 23.33 17.50 43.33
SQMEAN 102.88 52.67 25.50 25.30 22.70 52.50
EUPMEAN 101.13 50.79 24.17 28.14 23.37 49.50
2b. STANDARDIZED DATA
STNORSEM 0.96 0.28 -0.53 -0.44 -0.46 dag
STDOGONF 0.96 0.24 -0.55 -0.35 -0.49 0.20
STAUSM 0.98 0.26 -0.46 -0.42 -0.47 0.13
STJAPF 0.93 0.27 -0.55 -0.39 -0.47 0.22
MAXDIFF 0.05 0.04 0.09 0.09 0.03 0.09
STENEA 1.06 0.43 -0.04 -0.64 -0.81 0.01
STASNEA 1.02 0.44 -0.10 -0.79 -0.65 0.08
STAFARCH 1.04 0.24 -0.23 -0.46 -0.75 0.16
STSQ 0.94 0.27 -0.45 -0.46 -0.57 0.27
STEUP 0.93 0.24 -0.50 -0.35 -0.54 0.22
MAXDIFF 0.13 0.20 0.46 0.44 0:27 0.26
2c. REARRANGED DATA
STNORSEM 0.96 0.28 -0.53 -0.44 -0.46 0.19
STDOGONF 0.96 0.24 -0.55 -0.35 -0.49 0.20
STAUSM 0.98 0.26 -0.46 -0.42 -0.47 0.13
STJAPF 0.93 0.27 -0.55 -0.39 -0.47 0.22
STSQ 0.94 0.27 -0.45 -0.46 -0.57 0.27
STEUP 0.93 0.24 -0.50 -0.35 -0.54 0.22
MAXDIFF 0.05 0.04 0.10 0.11 OO. 0.14
STENEA 1.06 0.43 -0.04 -0.64 -0.81 0.01
STASNEA 1.02 0.44 -0.10 -0.79 -0.65 0.08
STAFARCH 1.04 0.24 -0.23 -0.46 -0.75 0.16
MAXDIFF 0.04 0.20 0.19 0.33 0.16 O15

discrete morphological characters, either they are not ancestral to those counterparts,
or regionality mainly evolved in the recent past (see for example Groves 1989;
Stringer 1992a and b; Wright 1992). Some (but not all) Australian fossils do show
modern regional characters, but I have suggested that this is because many of these
“Australian” characters were widespread in the Late Pleistocene, so that fossils in
Africa, Europe, and Asia also look “Australian” (Stringer 1992a and b). Even where
more carefully argued cases for morphological continuity between late archaic and
early modern specimens have been made (for example Smith & Trinkaus 1991;

MODERN HUMAN ORIGINS 12]

Frayer 1992) the characters are not generally those which are otherwise claimed to
be long-term regional markers. This suggests that the regionality of modern humans
is quite different from, and quite independent of, the regionality of premodern
humans.

If the proposal to place all hominids of the last million years or more in Homo
sapiens is not accepted, how can we best partition the fossil samples in relation to
modern humans and to each other? I have been quoted as denying that Homo erectus
was ancestral to Homo sapiens (for example Pope 1992:246), but my views have
probably been confused with those of a colleague (Andrews 1984). In fact, my view,
based on morphology and our present chronological framework, has not changed for
many years and is identical with that expressed by Harrison (1993), who otherwise
takes issue with the way that Andrews, Wood, and I approached “defining” the
species Homo erectus in 1984. Harrison states “if we exclude the possibility that all
Homo erectus populations across the Old World graded imperceptibly into Homo
sapiens ...,the presence of unique specializations in the Asian population may indeed
make it more likely that the African population 1s the ancestral population from which
Homo sapiens was derived.”

What Andrews, Wood, and | attempted to do, for the first time in detail, was to
see whether Homo erectus could be diagnosed by apomorphies, and especially by
autapomorphies. My view was that this could not be achieved if the Homo erectus
sample was taken very widely, but it was more successful if restricted to the Asian
hypodigm. However, I recognized that erectus-like features existed outside of the Far
East, in African fossils such as Olduvai Hominid 9, Bodo, and Omo-Kibish 2, and in
European ones such as Petralona, and | recognized that these indicated that an
evolutionary relationship probably existed between Homo erectus and “archaic
Homo sapiens” in the western Old World, even if such a relationship did not exist in
the East. The strict cladistic approach of the 1984 papers, emphasizing autapomor-
phies in search of a universal diagnosis of Homo erectus, is not something I would
advocate now, since I agree that we should attempt to recognize distinct fossil morphs
(= paleospecies) not by unique autapomorphies, but by unique combinations of
characters (whether plesiomorphies or apomorphies) compared with other morphs.

Having re-established that point, I would like to turn to the question of how best
to deal taxonomically with the range of variation in Pleistocene and recent Homo.
Here I do not want to discuss the question of the status of the earlier African fossils
such as KNM-ER 3733 and 3883 attributed by most workers to Homo erectus (for
example Rightmire 1990), by others to Homo leakeyi (Clarke 1990), and by yet others
to Homo ergaster (Wood 1992). I consider this issue to be unresolved from present
data.

Treating the early African specimens KNM-ER 3733, 3883, and Olduvai Hominid
9 as representing a single distinct morph (AFER), I have compared this group with
samples of Middle Pleistocene hominids from Africa (Broken Hill, Bodo, Ndutu,
Saldanha, Sale — AFMP) and Europe (Petralona, Arago, Steinheim, Bilzingsleben,
Vértessz6ll6s, Swanscombe, Ehringsdorf, Biache — EMP); late Middle to early Late
Pleistocene hominids of Africa (sample as Stringer 1992b, except for the parietal data

122 STRINGER

for Singa, omitted due to probable pathology — AFA); European Neanderthals (as
Stringer 1992b—ENEA); Skhul-Qafzeh (as Stringer 1992b — SQ); and a European
early Upper Paleolithic sample (as Stringer 1992b — UP). Logarithm and row stand-
ardized data for 39 measurements have been compared, as well as Penrose size and
shape analyses using 35 of these measurements (removing one of each pair of the
most highly correlated, as Stringer 1992b). The raw and Penrose size data show that
there have been significant increases from AFER to the Late Pleistocene hominids
in size, particularly for the EMP, AFMP, ENEA and AFA groups. However, shape
differences have also been extensive, and by no means all in the same direction.
Figure | shows a phenogram with the square root of the three largest shape
distances plotted to scale as a triangle, and the others given their approximate relative
positions. If we now plot the shape distances of the groups graphically, using facial
data (15 measurements) and vault data (20 measurements) and taking AFER as the
base point, Figure 2 1s produced. There is certainly no linear trend in shape changes,
and instead two main “trends” are evident. The ENEA, AFMP, and EMP groups show
greater changes from AFER in face shape than vault shape, while the SQ and UP
groups marginally show the opposite. AFA falls into an intermediate position.
Looked at from the perspective of the UP group, a much more linear arrangement 1s
produced with more equal face and vault distances (Figure 3). However, taking the
overall shape distances for the 35 measurements combined and plotting them against
estimated mean age (omitting AFER which has a comparable shape distance from
UP to AFMP, but a much greater time difference) produces Figure 4. The discrepancy
in the position of the Neanderthals is notable — they are almost certainly closer in
mean age to UP than either the SQ or AFA groups, yet they are much more distant
in shape. In fact they are at about the same shape distance from UP as the much older
EMP sample. Thus there is no straightforward progressive change leading to modern
humans of the kind advocated by Wolpoff e¢ a/. (1994) (nor, incidentally, is there

» AFER

FIGURE |. Phenogram showing shape distances between African early Homo erectus
(AFER), European Neanderthal (ENEA), and European Upper Paleolithic (UP) cranial sam-
ples (35 measurements). Approximate relative positions of African Middle Pleistocene
(AFMP), European Middle Pleistocene (EMP), African late archaic (AFA), and Skhul-Qafzeh
(SQ) samples added.

MODERN HUMAN ORIGINS 123

1800

1600

1400

1200

1000

Vault Shape from AFER

ao
So
o

a
o
o

1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400
Face Shape from AFER

FiGURE 2. Shape distances from AFER group for facial (15 measures) and vault (20
measures) analyses.

evidence for regional continuity in the-earlier samples, since I could have substituted
any of Howells’ modern geographical samples for the UP sample, with little effect
on the overall pattern of results).

I am happy with the present evidence for the discreteness of the taxon Homo
erectus from both Neanderthals and modern Homo sapiens, for example using its
suite of characters which contrast with those of Table 1. In my view the evidence for
the distinctiveness of a Neanderthal morph and Neanderthal lineage is almost as
impressive as the distinction between Homo erectus and modern Homo sapiens. The
combination of a highly derived facial morphology with a relatively primitive, but
still distinctive cranial vault, and the postcranial combination of probable primitive

1800 2 AFER

1600
1400

1200

from UP

1000

800

Vault Shape

600 800 1000 1200 1400 1600 1800
Face Shape from UP

FIGURE 3. Shape distances trom UP group for facial and vault analyses.

124 STRINGER

300000

250000

200000

150000

100000

Time before UP

50000

600 800 1000 1200 1400 1600 1800 2000
Shape Distance from UP

FIGURE 4. Overall shape distances from UP group versus estimated time difference (AFER
omitted).

skeletal characters (for example in the anterior pelvis) with a derived body shape
paralleling that of modern cold-adapted peoples (see for example Trinkaus 1981; Ruff
1991), marks the Neanderthals as a separate morph well worthy of specific recogni-
tion (see also Rak 1993). The proposed resurrection of Homo neanderthalensis King,
1864 has gained a number of supporters recently, including Harrison (1993), who is
otherwise rather cautious about the proliferation of species names in hominids. He
states “I would have to concur with Tattersall that if | found two morphs as different
as Neanderthals and modern humans in the Miocene, there is little doubt that | would
recognize them as two distinct species.”

I have previously argued, like Rightmire (1990), for the existence of a relatively
primitive Eur-African Middle Pleistocene hominid subspecies or species which lies
close to the common ancestry of Neanderthals and modern humans. This hominid
was probably contemporaneous with, but distinct from, Asian Homo erectus, con-
firming that cladogenesis had occurred. If we regard the Late Pleistocene morphs as
worthy of specific recognition as Homo neanderthalensis and Homo sapiens, the
specific name Homo heidelbergensis appears to be the most appropriate one for the
putative ancestral species. Referring back to Table 1, the characters of Homo sapiens
(sensu lato) could be made appropriate for Homo heidelbergensis by delineating
characters 1-5 as synapomorphies of the taxon shared with the Neanderthal and
modern human species, characters 6-11 as characters intermediate between those of
Homo erectus and later humans, and characters 12 and 13 as more advanced
characters lacking in the taxon.

However, recent research and discoveries have thrown the status of Homo heidel-
bergensis into some doubt (Arsuaga e¢ a/. 1993; Stringer 1993). As we have seen
from the previous phenetic analyses, AFMP and EMP (which might be assigned to
Homo heidelbergensis) predominately resemble Homo neanderthalensis, rather than

MODERN HUMAN ORIGINS 125

Homo sapiens, because data for AFMP and EMP are dominated by specimens such
as Broken Hill, Bodo, Petralona, and Arago, which share plesiomorphies in vault
form and, arguably, some apomorphies in facial form with Homo neanderthalensis.
Rak (1993) recognizes the uncertain status of these specimens by referring to them
as the “Kabwe (= Broken Hill) group.” The large series of cranial fossils from
Atapuerca has also shown up the problems of recognizing a separate European
species prior to the Neanderthals. | had previously differed from Wolpoff (1980) in
arguing that the contrasts between the Steinheim and Petralona crania warranted a
degree of taxonomic separation between them, rather than merely reflecting within-
population variation, especially dimorphism (Stringer 1981, 1985). However, the
Atapuerca material includes specimens resembling both Petralona and Steinheim.
Yet despite non-Neanderthal details such as a rather modern-looking (plesiomor-
phous?) temporal bone and parietal region, there are facial, occipital, and mandibular
aspects which clearly foreshadow those of the Neanderthals. If the Atapuerca sample
is really penecontemporaneous, it probably represents a primitive form of Homo
neanderthalensis, if we recognize the reality of that taxon. To then maintain that
Petralona represents a European species, Homo heidelbergensis, distinct from Ata-
puerca now seems more problematic. Perhaps more complete material of specimens
like those from Mauer and Bilzingsleben might show further consistent differences
from the Atapuerca range (e.g., in the occipital region and postcrania) which would
allow the maintenance of a distinct species, but this remains to be seen.

The situation in China and Africa is more complex still. The zygomaxillary
morphology of Broken Hill 1 and Bodo resembles that of Neanderthals (and Pe-
tralona) in some respects, whereas that of other African specimens such as Ndutu,
Thomas Quarry, Broken Hill 2, Florisbad, Ngaloba L.H. 18 and Jebel Irhoud | does
not. This could represent polytypism in the African Middle to early Late Pleistocene,
either locally developed or alternatively related to gene flow from another region
such as the Far East (Li & Etler 1992; Pope 1992). However, because the preservation
of the relevant regions in some of the Chinese material is by no means perfect, it 1s
unclear how much variation there really is in the East, and how distinct this is from
the pattern in the West. It is also uncertain how the African and Asian specimens
precisely relate to each other chronologically. If we were to link what Rak (1993)
calls the “Kabwe group” with Homo heidelbergensis through facial similarities, there
would remain a group of archaic African and Asian specimens which display a
zygomaxillary morphology more like that of modern Homo sapiens (although it
should be cautioned that the relevant morphology of Homo sapiens is by no means
as consistent as sometimes claimed). The (plesiomorphous ?) facial features of these
specimens would serve to distinguish them from Homo neanderthalensis and possi-
bly relate them to Homo sapiens, while there would also be some plesiomorphous
vault features found in early Homo neanderthalensis (e.g., Atapuerca). Some of the
specimens also show vault features which could be considered synapomorphous with
Homo sapiens, but there is considerable morphological variation even within the
Chinese and African samples, let alone when they are combined.

If a species were to be recognized which was distinctive from both Homo

126 STRINGER

neanderthalensis and Homo sapiens, and in Europe the name Homo heidelbergensis
was at the same time sunk into Homo neanderthalensis, two other nomina might be
appropriate. One would be Homo rhodesiensis, 1f the type specimen from Broken
Hill is judged to be distinct from the Neanderthal and modern human clades. Another
available name would be Homo helmei (Dreyer 1935), based on the Florisbad skull.
Homo helmei would then include A frican specimens such as Florisbad, Eliye Springs,
Ngaloba, and Irhoud, and probably also Asian specimens such as Dali, Jinniushan,
and, perhaps, Maba, Narmada, and Zuttiyeh. Yet another alternative, recently pro-
posed by me (Stringer 1992c), would be to extend the taxon name Homo neander-
thalensis to encompass all the European, African, and Asian forms previously
subsumed under the term “archaic Homo sapiens.” This proposal would downgrade
Neanderthal derived features of the face, vault, and body proportions to the level of
“racial variation,” and would emphasize shared vault and postcranial features which
were mainly plesiomorphous retentions from Homo erectus (see, for example,
Trinkaus, in press). | am not so happy with this proposal now, because I feel that the
Atapuerca finds and other unpublished research reinforce the special nature of
Neanderthal evolution in Europe, and this should be recognized taxonomically for
continuing research purposes. And that last statement is perhaps the strongest reason
for also resisting the proposal to sink Homo erectus into Homo sapiens. Such a
proposal can be the legitimate goal of a research program, and might be vindicated
in the long run, but we are a long way from establishing it. The premature extension
of the term Homo sapiens beyond the Late Pleistocene to the earlier Pleistocene, and
even Pliocene, would sound the death knell for meaningful systematic research on
Pleistocene hominids, and that is surely something that most of us do not wish to see.

The most useful phylogenetically-based taxonomy for Middle-Late Pleistocene
hominids would seem to be the recognition of at least four species: Homo erectus
(possibly continuing into the late Middle Pleistocene in eastern Eurasia and perhaps
even into the Late Pleistocene in Java); Homo neanderthalensis (Late Pleistocene of
western Eurasia, extending back to the Middle Pleistocene circa 200-300 Ka in
Europe, based on the Atapuerca evidence, or even 400 Ka based on Swanscombe);
Homo sapiens (Late Pleistocene, all regions); and a fourth species (Middle Pleisto-
cene, possibly extending into the Late Pleistocene, in Africa and eastern Eurasia and
perhaps Europe). Depending on whether holotypes are regarded as validly distinct
from the three species already named, the order of priority of nomina for this species
is: (1) Homo heidelbergensis; (11) Homo rhodesiensis, (1) Homo helmei.

Proposal 3: All Middle Paleolithic human fossils from the Levant represent
variants of a single population (and therefore species)
Proposal 4: The Skhul-Qafzeh samples are highly variable and have
been mischaracterized as “modern”

These proposals concern the classification of human fossils associated with the
Middle Paleolithic in the Levant (that is, the area adjoining the eastern Mediterra-
nean). There is growing evidence that Neanderthal and anatomically modern popu-

MODERN HUMAN ORIGINS 127

lations coexisted or alternated in their occupation of the region. However, it has been
argued that these are merely variants of a single Middle Paleolithic human population
(Wolpoff 1992) and that the Skhul-Qafzeh group is phenetically intermediate be-
tween Neanderthals and modern humans (Corruccini 1992).

The Levantine Middle Paleolithic fossil hominid record has long been controver-
sial (see for example McCown & Keith 1939; Howell 1957; Vandermeersch 1981;
Trinkaus 1984). Following new discoveries, further studies, and new radiometric
dating, the situation had seemed clearer, although not necessarily simpler in its
implications, with the recognition of two distinct populations — early modern and
Neanderthal — probably overlapping in time as well as space (see for example
Stringer 1988; Griin & Stringer 1991; Bar-Yosef 1992; Rak 1993). However, other
workers have argued for a return to the views of McCown & Keith, for only a single
morphologically variable population during the Middle Paleolithic. For example,
Wolpoff (1992) has stated “the amount of variation in measurements from the Middle
Paleolithic people from the Levant appears to be less than that in a modern popula-
tion.” This view was challenged by van Vark & Bilsborough (1991), who used
Howells’ modern data base to show that the generalized distance (D’) between an
Israeli Neanderthal specimen (Tabun) and three early modern specimens (Skhul 5,
Qafzeh 6 and 9) was significantly greater than the distance between recent “Eskimo”
and “Bushman” samples, supporting Rak’s view (as cited in Culotta 1991). Wolpoff
(1992) used ranges of 13 cranial measurements for the Israeli fossils compared with
those of a larger British sample to show that the latter single "population" had the
greater degree of variation, but he did not address the issue of differences in pattern.
When, instead, the variation in measurements is compared using the respective
standard deviations, the Levantine sample is certainly more variable overall than the
much larger recent one (van Vark, pers. comm.). Wolpoff’s (1992) comparisons of
the variation in Middle Paleolithic and recent samples have also been strongly
criticized on statistical grounds by Foote (1993).

I think it is the pattern of measurement differences which seem most important
here, and it has been demonstrated many times that the Levantine Neanderthals (as
well as those from Shanidar) are distinct metrically and morphologically from the
Skhul-Qafzeh sample (Stringer 1974, 1978, 1989, 1992b; Stringer & Trinkaus 1981;
Vandermeersch 1981; Trinkaus 1983, 1984, 1992). The Asian Neanderthals show
the presence of Neanderthal apomorphies of the face, mandible, cranial vault, and
body shape, but some of these features occur at lower frequencies than is the case for
the European Neanderthals. Thus for the standardized measurements of Table 2, the
Asian Neanderthals are like the European Neanderthals in four measurements (NLH,
SSS, FRS, and OCF; see also Stringer 1992b), but are more like archaic African, and
modern, crania in two others (BNL, PAS). A whole suite of postcranial features also
distinguish the Asian Neanderthals from the Skhul-Qafzeh samples, although many
of these are likely to be plesiomorphous in the Neanderthals, including those of the
pubic ramus, as already discussed (Trinkaus 1983, 1984, 1986, 1992; Rak 1990,
1993). There are also a few similarities between some of the Asian Neanderthals and
the Skhul-Qafzeh samples. These include the flatter midfaces of Tabun | and

128 STRINGER

Shanidar 2 and 4, and the parietal proportions of Shanidar |. The former features may
be related to the greater age (and/or plesiomorphous nature) of the specimens or to
regional variation in the Neanderthals, while the latter could represent an individual
variation or a reflection of gene flow from non-Neanderthals. Phenetic comparisons
(Stringer 1991) suggest that the Saccopastore early Neanderthals, the late European,
and the Asian Neanderthals, are about equally related to each other, and it is possible
that some of the early Neanderthal morphology (for example rounder occipital
profile, larger mastoid processes) was retained to a greater extent in the Asian
Neanderthals. On the other hand, without yet having clear data on the body shape of
the early Neanderthals, we are presently unable to determine whether the presence
of similar limb proportions in the European and Asian Neanderthals is due to common
inheritance, continuing gene flow, or (less probably) homoplasy.

Thus, the kind of systematic approach that I (and others like Vandermeersch,
Trinkaus, and Rak) use, recognizes a significant division between the Asian Nean-
derthals and the Skhul-Qafzeh sample, whether this is regarded as subspecific or
specific. This approach is disparagingly referred to as “replacement systematics” by
Clark & Lindly (1989), but I would prefer to use another r-word — “reality systemat-
ics” — for this division. Two “morphs” are recognizable, and while they overlap in
some respects they are quite distinct in others. One is Neanderthal-like in predominant
pattern, while the other has been termed “anatomically modern” by a number of
workers.

A clear initial impression of the degree of modern affinity can be gained by a
comparison of the fossil group means with the overall means for modern humans
obtained from Howells’ large (n = circa 2,400) recent cranial series. The early Upper
Paleolithic sample is distinct at the + 2 standard deviation level in only one out of 36
measurements (skull length), the Skhul-Qafzeh group in 6 measurements, the African
late archaics in 12, the Asian Neanderthals in 16, and the European Neanderthals in
20. While such a simple comparison does not distinguish factors of shape from size,
there is evidently a gulf in modern affinities here between Skhul-Qafzeh and the two
Neanderthal samples, and this brings us on to Corruccini’s (1992) views on the
Levantine fossils (Proposal 4).

In an interesting review of the Skhul material, Corruccini stated that Skhul 5 was
usually the only specimen considered in discussion of the modernity of the material,
and that when Skhul 4 and 9 were considered as well, metrical variation produced a
much greater overlap with Neanderthals. He also claimed that Qafzeh 6 was cranio-
phenetically closer to Neanderthals than to a European Upper Paleolithic sample.
Dealing with the first point, | have always used Skhul 9 in comparisons where it
provided relevant data (for example Stringer 1974, 1978, 1989, 1992b; Stringer &
Trinkaus 1981), and as a specimen under my care, it is very familiar to me. However
it is, contra Corruccini, far less complete and well-preserved than Skhul 5, and
therefore of more limited value. I would agree that its parietal region is more primitive
in shape than that of Skhul 5 (see for example Stringer 1978; Stringer & Trinkaus
1981), but I would argue that this is not necessarily a Neanderthal feature, and could
relate it just as easily to late archaic African specimens (see the comparisons of Table

MODERN HUMAN ORIGINS 129

2 for parietal subtense, PAS). When the pelvis and femur of Skhul 9 are also
considered, this specimen shows a high femoral neck angle, rather than the lower
angle more characteristic of archaic hominids (Trinkaus 1992). As Corruccini (1992)
notes, it does have a relatively long (although quite thick) pubic ramus, but this feature
is less Neanderthal-like when standardized for body size (Trinkaus 1984). For Skhul
4, the cranial preservation is arguably worse than for Skhul 9, and I could take
virtually no reliable measurements on the specimen, but the postcranial morphology
is better preserved and clearly “modern.” Unfortunately, in his analyses, Corruccini
appears to have used the McCown & Keith (1939) data on Skhul 4 and 9 without any
detailed examination of the fossils themselves. Thus he seems to have failed to
recognize why most of the cranial measurements published by McCown & Keith are
bracketed (they are uncertain or estimated). In McCown & Keith’s Tables 73-79, the
following number of cranial measurements are given (bracketed number gives
numbers of measurements estimated): Skhul 5, 63 (4 estimated); Skhul 4, 61 (37
estimated); and Skhul 9, 54 (41 estimated). Thus Skhul 5 rightfully predominates in
discussion about the site because of its better cranial preservation, not because of any
inherent bias on the part of researchers.

When we consider the Skhul-Qafzeh sample as a whole, I agree with Corruccini
about its phenetically intermediate nature between archaic (not specifically Neander-
thal) and recent humans, but I would see this as reflecting an early modern morphol-
ogy which still retains a number of primitive features. If the Skhul-Qafzeh sample is
seen as metrically intermediate between recent and archaic humans, the archaic
humans it most clearly resembles are the African late archaics followed (with less
certain data) by the Dali-Maba sample (Stringer 1992b, 1994). In attempting to stress
the differentiation of the Skhul-Qafzeh group from the Neanderthals, workers such
as myself have probably overemphasized the cranial modernity of the specimens (as
distinct from their clearer postcranial modernity). However, when the largest possible
data sets are used, the Skhul-Qafzeh sample can justifiably be grouped with recent
Homo sapiens on the basis of synapomorphies such as a rounder cranial profile
(frontal, parietal, and occipital shape), mental eminence, pelvic and femoral structure,
and symplesiomorphies such as a low face and nasal height combined with a flatter
midface. Plesiomorphous retentions such as the broad (but short) face, relatively
flatter parietals in some specimens, greater total facial prognathism, broad nose,
larger dentition, and palatal dimensions are those which lead to an intermediate
phenetic position between archaic and modern, but there is little indication of any
specific Neanderthal relationship.

Instead there is evidence of a prior archaic ancestry, which should surprise no one
who believes in human evolution — we should not expect 100,000-year-old mem-
bers of our species to look exactly like living people. Corruccini suggests a revival
of the pre-Neanderthal formulation of modern human origins (see for example
Howell 1957), and I came close to this conclusion in my earlier research (Stringer
1974). Now I would argue that specimens like Jebel Irhoud are the persisting African
equivalents of the pre-Neanderthals — representatives of populations which have
retained a rather generalized cranial form from the hypothesized common ancestor

130 STRINGER

of Neanderthals and modern humans. We differ over the data and its interpretations,
but both Corruccini and I recognize the intermediate nature of the Skhul-Qafzeh
group, although we might place them on opposite sides of any archaic-modern divide.
We also recognize the late evolution of the fully modern form and modern regionality,
and the probability that the late Neanderthals of Europe were not ancestral to modern
humans.

Finally, | agree with Corruccini that the large internal variation of the Skhul-
Qafzeh sample is an important and still largely unexplored issue. For example,
Qafzeh 6 and 9 differ markedly in facial shape (from my own observations and data,
and van Vark & Schaafsma 1992), and there is the possibility that these human
samples cover a greater range in time than recently assumed (McDermott er a/. 1993),
which is now under further investigation. Nevertheless, the overall cranial and
postcranial data for Qafzeh and Skhul show that in the early Late Pleistocene Israel
was inhabited by people showing clear synapomorphies with modern humans, while
Neanderthals persisted in western Eurasia and while the Ngandong people may still
have lived in Java. Africa is the only other region with comparably early evidence of
modern human apomorphies, even though the evidence is either less complete or less
well dated (for example the Klasies fronto-nasal fragment 16425, mandible 16424,
Omo Kibish 1, Mumba, Die Kelders, Guomde KNM-ER 999 and 3884, and, possibly,
Border Cave 1, 2, 3, and 5; see for example Brauer 1992; Trinkaus 1993).

Concluding Comments

Some workers have evidently become tired of discussions about hominid sys-
tematics and seem to wish to set aside the whole process of classifying fossil material
(e.g., Trinkaus, in press). However, this process is fundamental to the proper study
of the material, whether we are carrying out comparative functional analyses,
reconstructing phylogeny, or creating evolutionary scenarios. All of these require the
comparison of fossil units (morphs), and the construction of, and relationship be-
tween, these morphs cannot just be set aside, whatever difficulties may be entailed.
I believe that the most distinct Middle-Late Pleistocene morphs should be allocated
to distinct species. Pleistocene Homo (excluding Homo habilis from consideration)
is therefore most reasonably divided into a minimum of three species: erectus,
neanderthalensis, and sapiens. At least one further species should be recognized,
which probably represents the stem species from which both Homo neanderthalensis
and Homo sapiens evolved, assuming that they did not descend directly out of Homo
erectus. This species may be named Homo heidelbergensis, Homo rhodesiensis, or
Homo helmei, and it will require further study of existing fossils, as well as new
discoveries, to resolve this very current issue satisfactorily.

Acknowledgements

I would first like to thank the organizers and sponsors of the meeting for inviting
and supporting my participation in an excellent Symposium. | would also, as always,
like to thank all those who have given me study access to fossil hominid material.

MODERN HUMAN ORIGINS 131

Finally I would like to thank Robert Kruszynski for his help in preparing the figures,
and Irene Baxter for her help in preparing the manuscript.

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CRANID — A computer program for forensic and other applications. Archaeol. Oceania
27:105-112.

Behavior and Human Evolution

Alison S. Brooks

Department of Anthropology
George Washington University
Washington, DC 20057

Behavior is critical to an understanding of human evolution, as it underlies not
only definitions of “humanness” but also some of the major species distinctions
within the genus Homo. Yet behavioral and morphological shifts in the evolution-
ary history of Homo do not always coincide. Fossil behavior can be reconstructed
both from the morphology, chemistry, pathology, and disposition of the fossils
themselves and from the artifacts, faunal remains, and sites of the archaeological
record. A review of behavioral evolution in the genus Homo suggests that we do
not yet have behavioral evidence to support more than one species of earliest Homo
between 2.3 and 1.6 Ma. Niche differentiation in behavior may exist, but is either
not reflected in the record or not accessed by our current analysis techniques.
Similarly, although the replacement of H. habilis by H. erectus (sensu lato) is indeed
accompanied by major behavioral change, the later shift from H. erectus to H.
sapiens is less clearly associated with behavioral evolution. Finally, there is evi-
dence for a major behavioral change coinciding with the appearance of anatomi-
cally modern humans, H. sapiens sapiens, which includes the earliest appearance
of this taxon in Africa. In this case, the behavioral evidence supports separation at
the species level of modern from archaic sapiens.

Arguably the most frequently asked question in public symposia on human
evolution 1s: “How human are the fossil taxa variously assigned to Australopithecus
or Homo?” What is humanness anyway? Few would argue that the essence of
humanness is walking on two legs, although that is how we used to define “hominid”
before genetics, paleontology, and cladistic methodology suggested that this term
might cover the African apes as well (Delson et al. 1977; Schwartz et al. 1978).
Humanness is more likely to be thought of in behavioral terms: technological, social,
cognitive, aesthetic, moral, or symbolic behavior.

How do we know the thoughts of early hominids, or what they did ona daily basis?
Did they live in a world that was partly created or built by themselves through the
making of tools, buildings, and public and private spaces? Did they know where their
next meal was coming from, or just run into it in a haphazard sort of way? Did they
mate for the long term and maintain ties to adult children throughout their lives? Did
they achieve senior citizen status, care for each other’s wounds and illnesses, or bury
their dead? Did they enjoy the company of friends from afar or decorate themselves

Contemporary Issues in Human Evolution Memorr 21, Copynght © 1996
Editors, W.E. Meikle, F.C. Howell, & N.G. Jablonski California Academy of Sciences

136 BROOKS

and their environment? Was meaning invested in arbitrary symbols: sounds, shapes,
colors, or gestures?

In biology, not only is behavior an important component of an animal’s ecology,
but often part of what separates it as a species from closely related forms (Dobzhansky
1937; Mayr 1963). Behavior can keep members of different species from meeting,
mating, or raising successful offspring. In other words, 1f a potential mate’s dance
does not turn you on, you might as well be living on different continents. Behavior
is thus integral to an understanding of the species definition, although both systema-
tists and paleontologists try to base the actual definitions entirely on morphological
data (Eldredge 1986, 1993; Tattersall 1986; Albrecht & Miller 1993; Kimbel &
Martin 1993: Kimbel & Rak 1993). Darwin (1859:76) and his successors (Dobzhan-
sky 1937; Mayr 1963) have generally argued that closely related species experience
the greatest competition for resources and can only coexist if they use the environment
differently. By analogy, phylogenetic species in the same environment should also
differ in their niche behavior (Mayr 1950). An absence of behavioral differentiation
would call the species distinction itself into question.

In the study of human evolution, species definitions have often been underlain,
overtly or covertly, by supposed behavioral distinctions. The clearest example is
Homo habilis, a taxon established initially to distinguish the first tool-making forms
from non-tool-making predecessors,' although some of the eventually included
specimens (e.g., OH 24) overlapped to a marked degree morphologically with
Australopithecus, while some later forms exhibited certain convergences with fossils
previously assigned to Homo erectus. In fact, the inclusion of habilis within Homo
required a change in then-prevailing morphological definitions to accommodate the
smaller cranial capacities typical of the habilis group (Leakey et al. 1964; Napier &
Tobias 1964).

The evolutionary history of our own genus, Homo, usually involves the recogni-
tion of at least three different species, H. habilis, H. erectus, and H. sapiens, and at
least two subspecies of the latter: archaic Homo sapiens (and/or Homo sapiens
neanderthalensis) and Homo sapiens sapiens, anatomically modern humans.’ The
morphological boundaries are defined to a great extent by reference firstly to
increasing brain size with its accompanying changes in cranial shape, and secondly
to decreasing dental size with the accompanying reduction in the face and cranial
structures associated with mastication (McHenry 1982). Are there behavioral differ-
ences between these forms as well? How can we determine their behavior? The
remainder of this paper will examine the behavioral evolution of Homo and discuss
the fit between the evolution of humanness and the evolution of Homo, as defined
morphologically.

The Study of Behavior

Sources of information on behavior are limited to the evidence from the fossils
themselves and the evidence from the associated artifacts, animal bones, and land-
scapes which can be termed the archaeological record. A modern analogy, observed

BEHAVIOR AND HUMAN EVOLUTION 137

or experimental, also underlies most behavioral inferences. We compare the evidence
from the fossil or archaeological records with natural bone accumulations (Tappen
1992), the wear on modern teeth (Brace ef a/. 1981) or stone tools (Odell 1977; Keeley
1980; Vaughan 1985), tooth marks on bones in zoo cages (Haynes 1981) or hyena
dens (Sutcliffe 1970; Avery 1984; Potts ef a/. 1988), effectiveness of projectile shape
determined by experiment (Knecht 1993), relationship of sexual dimorphism to
mating behavior in modern apes (see review by Frayer & Wolpoff 1985), or of
landscape aridity to group organization in modern hunter-gatherers (Binford 1980,
1982, 1983; Laden & Brooks 1994; Brooks & Laden, in press). These always carry
a caution that modern analogues or experiments may not adequately represent the
fossil conditions, environments, or behaviors.

Behavior may be inferred from fossils in a number of ways, including their
morphology (and signs of violence, stress, or disease), their chemistry, and the
disposition of the fossils themselves, in a hyena den or in a cemetery, as an articulated
skeleton or a jumble of skulls bearing cutmarks (Table 1).

In inferring behavior from morphology, one might use limb proportions and the
shape of the digits to determine the habitual ecological niche. Did the species still
have short legs, long arms, and curved digits for sleeping in the trees (Susman et al.
1984)? Are there adaptations for heat loss, such as bipedalism itself (Wheeler 199 1a,
199 1b, 1992a, 1992b), or aspects of the venous flow to and from the brain (Falk 1986,
1990; but see Wheeler 1990; Dean 1990), which might imply activity in the heat of

TABLE |. Behavior from Fossils

Morphology
Habitual ecological niche: trees/ground, diurnal/nocturnal
Locomotor pattern
Manual dexterity—need to grasp branches or manipulate
Need for learning, memory storage, pattern recognition
Language capability
Diet—coarseness, quality (calories/gm.)
Diet—use of tools to pre-crush or predigest food
Lifespan—structure and length

Infancy

Adolescence
Male-female relationships
Male-male relationships
Disease and stress, inter- and intra-group relationships

Chemistry

Diet—quality, meat vs. vegetable food, roots vs. leaves
Ecological niche

Climate

Post-mortem treatment

Consumption or predation

Primary burial, with or without artifacts/grave goods
Secondary burial, defleshing

Cemeteries—have settlement pattern implications

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the day to avoid predators? How efficient was their bipedalism (Taylor & Rowntree
1973; Rodman & McHenry 1980; Rak 1991)? The curvature of the thumb, its joint
with the wrist bones, and shape of its tip might imply capacity for fine manipulation
of objects (Susman 1988; Ricklan 1987; Tobias 1991). Hyper-robust limbs, joints,
and muscle markings imply extreme physical stress in hunting or defense (Trinkaus
1983b, 1986) or development of a calcium reserve in a shift to carnivory (Kennedy
1992), while more gracile limbs may imply long-distance or tool-mediated hunting
(Brace 1992, 1995). The size of the brain, and certain aspects of its shape such as
asymmetry, arrangement of sulci, or presence of areas in the left temporal lobe, imply
selection for cognitive skills: learning, memory storage, and pattern recognition, as
well as for symbolic communication or language (Tobias 1991; Falk 1987a, 1987b).
The shape of the cranial base and the vocal tract may also suggest ability to speak
(Laitman et al. 1979; Lieberman 1984). Body size or stature 1s a clue to dietary shifts
(Ruff 1987; Ruff & Walker 1993). Primates in open savannas are generally baboon-
size or smaller; australopithecines are similar, but in Homo erectus we see a major
size increase implying a shift in dietary quality (calories/g). Poor quality foods are
not easily transported and shared owing to their bulk, so food quality might even
imply social organization or lack thereof (Foley 1987; Tooby & DeVore 1987, contra
Lovejoy 1981). Body size and shape may also relate to climate or activity levels (Ruff
etal. 1993, 1994).

Teeth are a major source of information about not only diet but also technology
and social life (see review by Gordon 1993). Smaller chewing teeth ona bigger animal
imply either a major dietary shift to softer foods or preparation and predigestion of
those foods outside the mouth by pounding or cooking. Smaller and/or monomorphic
canines may be a secondary result of post-canine megadonty, may imply monoga-
mous pair-bonding and territoriality, as among the gibbons, or even the invention of
new and different ways for males to compete for females. Enamel thickness may
reflect the hardness or grittiness of food sources (Martin 1985), while enamel
structure and tooth eruption patterns tell us about how rapidly the teeth form, and thus
how rapidly an infant grows up (Smith 1991). Finally, the wear on teeth can indicate
use as tools for manufacturing, stripping, or clamping (Trinkaus 1983a) in the anterior
part of the mouth where chewing stress is unlikely, as well as how early in life babies
begin to eat solid food (Skinner 1981, 1989). This last is not trivial, since our present
population crisis may be partially attributed to earlier weaning of the young. Are
males much bigger than females, implying possible extreme competition for mates
and harem-formation, as in gorillas? (See, for example, reviews of this issue for 4.
afarensis in McHenry 1991 and Kimbel et al. 1994.)

A shift to more predatory food procurement strategies was not without cost
(Shipman & Walker 1989). Signs of stress such as enamel hypoplasias and Harris’
lines tell us how reliable the food supply was, while injuries attest to predation, as in
the case of an Australopithecus with leopard tooth marks in its skull (Brain 1968,
1981), and interpersonal violence (e.g., the inflamed knife wound in the back (ninth
rib) of a Shanidar Neandertal: Trinkaus 1983a). Healed injuries, such as those of the

BEHAVIOR AND HUMAN EVOLUTION 139

Shanidar Neandertal with a healed severe injury to the right arm, may also point to
the emergence of moral behavior.

The relatively new field of bone biochemistry can indicate both diet and habitat
of the past. The concentration of strontium (Schoeninger 1979; Sillen 1981, 1992,
1993) tells us how much meat (or roots) a fossil human ate, while the concentration
of carbon-13 tells us how much of the diet was derived from tropical grasses or aquatic
resources (Price ef a/. 1985; Tuross & Fogel 1993). Nitrogen isotopes can indicate
dietary quality (Schoeninger et a/. 1983), weaning age (Fogel et a/. 1989), or whether
the individual was starving at the time of its death (Tuross & Fogel 1993). Both carbon
and oxygen isotopes can also indicate climate: oxygen-18 is more concentrated in
colder periods, while tropical grasses with lower 'C values will expand in dry periods
at the expense of forests (Cerling 1992).

Finally, the disposition of the remains is a primary indication of behavior. Are
these fossils lying under their living sites or in the lairs of leopards (Brain 1981)? Are
they buried deliberately or simply left out haphazardly? Are the bones articulated, or
are there signs that this is a collection of disjointed parts in a secondary burial? Are
there cutmarks on the bones? Were these made when the bones were fresh, suggesting
cannibalism or scalping (Smith 1976; Trinkaus 1985; White 1986), or when the bones
were dried, during defleshing and secondary burial? Are a number of individuals
buried together in a cemetery or mass grave such as the epipaleolithic one near Jebel
Sahaba, Egypt (Wendorf 1968), or the large concentration of “pre-Neandertals” from
Atapuerca in Spain (Bahn 1996; Arsuaga er a/. 1993)? Is this a mass disaster,
indicated by a single set of prehistoric excavations or structures, or a sequential use
of the place for this special purpose over a long period of time, indicated by
overlapping sediment accumulation pits, or structures?

A somewhat different range of behaviors may be derived from examining the
archaeological record (Table 2). Stone tools can be analyzed in terms of raw material,
technology of manufacture, function, and style or design, as well as how each of these
changes over time and space. The distance the raw material was carried from its
source tells us about cognitive planning for aesthetic and function-specific ends,
about locomotor behavior, ranging pattern, and even intergroup relations if trade was
involved (Toth & Schick 1993; Merrick etal. 1994). The process of manufacture may
indicate cognitive organization and handedness (Toth 1987) or the ability of the
artisan to visualize the final shape in the mind, as well as the technological sophisti-
cation and understanding of material properties of particular stones, much as
Michelangelo envisaged the “David” in a block of damaged marble. What the tool
was used for can be determined from patterns of damage and from residues (Loy
1983) or polishes (Keeley 1980) by reference to experimentally-induced wear and
damage. What happens to a bone knife if you cut up a mammoth with it? At the
Smithsonian, several years ago, my colleagues spent a few days cutting up a dead
elephant named Ginsburg in order to find out (Stanford 1979). The shapes of tools,
and the degree to which size and shape were standardized, can indicate hafting or use
of projectiles (Shea 1988), both of which require more standardization. Alternatively,
standardization may simply suggest the cognitive skills of the makers. If shape

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TABLE 2. Behavior from Archaeology

Stones

Raw material source — transport and trade

Shape: cognitive imagination, thinking ahead

Functions — (from residues or wear)

Use of symbols — in shape or design

Rates of change in space and time, similarity to “culture”

Re-use and reworking, planning, landscape use, raw material conservation

Bones

Species represented: large or small, easy or dangerous, herd or individual

Ages and sexes: human hunting competence, methods, selectivity

Skeletal parts: scavenging or hunting, transport or on-the-spot consumption,
surfeit or scarcity

Season of death: seasonality and scheduling of landscape use

Damage, breakage, cutmarks and toothmarks: use of animal products,
scavenging or hunting, site-use pattern

Sites

Distribution of residues on the landscape

Group movements, scheduling and re-use, cognitive maps
Relation to paleogeography, why were certain places important
Relation to paleoenvironment

Comparison of site contents: activity differences in space
Status or class differences

Gender bias in the record

changes dramatically from one region to the next, we may be looking at ethnic or
cultural differences, symbols of group identity (Wiessner 1983; Sackett 1977, 1980,
1982: Wilmsen 1974; Hodder 1985). Finally, the life history of the tool after it was
made, whether it was re-used, re-sharpened, or dropped and later recycled into
something else tells us about re-occupation and scheduling of landscape use (Binford
1979: Kuhn 1991, 1992, 1995). Recycling may indicate higher levels of “human-
ness,” requiring a concept of the future, or simply a greater degree of territoriality
and re-use.

Bones of prey animals also carry behavioral information. Were the species
involved large or small, gregarious or solitary, dangerous or easy to kill (Klein 1978)?
Each of these implies certain needed technological or even social and cooperative
skills to hunt successfully. Ages and sexes of the prey also suggest the competence
of the hunter, since competent humans may tend to take more big prime age males
than other carnivores (Brain 1981; Klein 1982; Kuhn & Stiner 1994; Stiner 1994). If
all ages and sexes are present —a “catastrophic” mortality profile — the hunt may
have been a wholesale slaughter or ambush of an entire group. The skeletal parts of
the prey animal have behavioral implications: lots of limb bones may mean the meat
was transported to the site, while the axial skeleton and skull of a big animal might
indicate the location where the animal was actually butchered or eaten (e.g., Bunn &
Kroll 1986). Was the meat obtained by scavenging or by hunting? Over-repre-
sentation of distal limb segments or skulls may indicate scavenging, what was left

BEHAVIOR AND HUMAN EVOLUTION 141

after the carnivores were finished. The presence of articulated skeletons among the
prey may show that they had much more than they needed for food (Frison 1993).
Seasonal scheduling of visits to the site will result in prey animals who all died in the
same season. This can be demonstrated through study of the growth layers in tooth
roots (e.g., Lieberman 1993; Spiess 1979). The pattern of damage and breakage of
bone and the presence of carnivore toothmarks are major clues to behavior. For
example, stone tool cutmarks over toothmarks of carnivores might imply scavenging,
while toothmarks over cutmarks imply that the people did not stay in one place long
(Blumenschine et a/. 1994). Carnivores would not visit the site while the people were
there, and bones lose interest for most carnivores after a week or two (Yellen 1991).

Archaeological sites, or the distribution of residues on the landscape, are perhaps
the most interesting and neglected aspect of archaeology; indeed, the very existence
of such concentrations was a major feature of the initial development of Homo. In
nomadic hunter-gatherer groups, visible residues are most likely to result from
re-occupation rather than from a single visit (Brooks & Yellen 1987; Binford 1983).
Re-use itself implies a cognitive map of the landscape, and might indicate a seasonal
round of activities.

Site locations may imply dietary selection and procurement strategy (Stahl 1984;
Sept 1992). What are the landscape features associated with such concentrations?
High points? Caves? Open air locations? River margins? Gallery forest? Stone
outcrops? How do these change as species of Homo change, or with changing
environments? Finally, are all sites the same in what they contain? Are some sites
full of projectiles, while others are full of scrapers, possibly representing male and
female activities respectively (Binford & Binford 1966)? Are some sites richer in
exotic raw materials, ornaments, or specially constructed features than others? Could
these be ceremonial centers, or Nob Hills of the past where some individuals
controlled a disproportionate share of the scarce goods (e.g., Soffer 1985)?

Behavioral Evolution in Homo

From the twin perspectives of the archaeological and fossil records, we turn now
to a consideration of species definition in Homo. What are the major behavioral shifts
in human evolution? (See Table 3.) Do they co-vary with major morphological shifts
that mark species boundaries? If not, why not? Is it because the two species in question
did not differ in behavior, in which case it would be difficult to justify their separation
at the species level? Or is it because we cannot document the difference, either
because it left no trace or because we are not reading the record correctly?

Homo habilis

Homo habilis, whether sensu strictu or lato (see Wood, this volume) is generally
accorded the primary place at the base of the lineage of Homo, beginning as early as
2.3 Ma. It was first defined as a behavioral species, whose morphological consistency
was debated from the beginning. In behavioral morphology it is the first non-
megadont bipedal hominid, with a significant increase in brain/body-size ratio

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TABLE 3. Major Behavioral Shifts in Human Evolution

1. Initial concentration of tools and food residues on the landscape, adaptations to heat (H. habilis)

2. Habitat and niche expansion to mid-latitude temperate zones, fire and symmetry, projectiles and
hunting, long adolescence (H/. erectus)

3. Habitat and niche expansion to high latitudes, symbolic behavior, long-distance social networks and
social complexity, environmental modification (H. sapiens sapiens)

(Tobias 1991). The smaller teeth of many individual fossils may indicate the use of
tools for pre-processing food. Postcranial morphology and body size, however, may
indicate that, like Australopithecus, it still spent a lot of time in the trees (Susman et
al. 1984; Aiello & Wheeler 1995). The thumb’s carpo-metacarpal joint and apical
tuft or tip are similar to those of the robust australopithecines, implying a similar
capability for manipulating tools (Susman 1988; Tobias 1991). The larger brain and
possible Broca’s area imply more capacity for learning, while the venous drainage
pattern may suggest that H. habilis was active at midday (Falk 1986, 1987b, 1990,
1992; but see Wheeler 1990; Dean 1990). Although much debated, the enamel growth
and eruption pattern of the teeth may suggest that the long-adolescence pattern of
humans had not yet developed (Bromage 1987; Smith 1991). Size differences and
implied sexual dimorphism are extreme to an extent inconsistent with the common
human social pattern of today: pair bonding in a multi-male grouping (Frayer &
Wolpoff 1985).

Behavioral archaeology indicates that H. habilis was limited to the African tropics
and sub-tropics, although a recent much-debated claim places this species in South
China as well (Huang ef al. 1995). Stone tools consist mostly of flakes and cores,
with no consistent shapes (Chavaillon 1976; Merrick & Merrick 1976; Kibunjia ef
al. 1992; Toth & Schick 1993; Rogers et al. 1994). Raw material was transported
about 3km at Olduvai (Schick & Toth 1993). Sites themselves are important
indicators of changing hominid behavior on the landscape, as none occur before 2.5
Ma. They are probably not home bases or living sites, as their locations on lakeshores
are not consistent with safe sleeping places (Brooks & Yellen 1987). It is quite
probable that hominids were still sleeping in the trees.

Bones imply that most meat was scavenged (Shipman 1986; Potts 1988; Bunn &
Kroll 1986). There is no evidence for symbolic behavior. This was not a human way
of life. The correspondence between behavior and species boundary is hard to
determine, although the first tools at Gona and Lokalele at 2.5 Ma may not signifi-
cantly predate the first H. habilis at 2.3 to 2.1 Ma (Hill et al. 1992; Schrenk eg al.
1993; Rogers et al. 1994). H. habilis’ behavioral niche was not too wide, as this
species coexisted throughout with at least one other hominid: 4. robustus/A. boisei,
and possibly with others (see Wood, this volume). Because the two species co-occur,
we cannot be sure that 4. boisei/robustus did not also make tools; their thumb
morphology is similar (Susman 1988). One possible clue to the difference between
the two is bone biochemistry. Australopithecus robustus may have fed on roots and

BEHAVIOR AND HUMAN EVOLUTION 143

a surprising quantity of meat (Sillen 1993); preliminary data on Homo, however, is
very similar (Lee-Thorp & Thackery 1996).

Homo erectus

The next species in the lineage of Homo, H. erectus (or H. ergaster if the East
African forms are considered a different species as per Wood 1984) appears alongside
H. habilis and A. robustus by 1.7 Ma. This is a major morphological species boundary
in human evolution (Rightmire 1990). It used to be considered less significant in
terms of behavior, as some “Oldowan” tools continue to be made (Leakey 1971).
More recently, however, it is evident that H. erectus also represents a major behay-
ioral shift. In behavioral morphology, it had smaller molars but larger body size and
brain/body size ratio. This goes against the hypsodont trend of other large mammals
at 1.6 Ma, suggesting that H. erectus must have solved the food problem in open
environments through tools. Enamel microscopy suggests that childhood and adoles-
cence were closer in pattern to ours (Smith 1993; Ruff & Walker 1993). As a long
adolescence would prolong the most dangerous period for most mammals, length-
ened adolescence itself suggests changes in social life to protect and even feed
adolescents. At Nariokotome, a 12-year-old boy was already ca. 5'4-5" tall, implying
a modern adult size and large early growth spurt (Walker 1993; Walker & Leakey
1993). In humans this requires an adequate protein source, such as meat provided by
hunting. Brain cooling is modern, suggesting diurnal activity in an open environment
(Falk 1990, 1992). The presence of asymmetry and possibly of Broca’s area imply
language capability, although not necessarily speech (Begun & Walker 1993). The
limb proportions and curvature of the digits are modern; H. erectus did not live in the
trees.

The archaeology of H. erectus also suggests a major behavioral shift. Its distribu-
tion is distinctive; it expands out of the African tropics/subtropics to northwest Africa
and the Eurasian subtropics by 1.4 Ma or earlier (Tchernov 1987; Sahnouni 1987;
Bar-Y osef 1991; Dzaparidze et al. 1992; Swisher et al. 1994; Gabunia & Vekua 1995;
Huang ef a/. 1995), and well into the temperate zone by 1.1 Ma (Woo 1966; Wu &
Olsen 1985; Brooks & Wood 1990; Schick & Dong 1993). This first population
explosion implies successful exploitation of a new food source with a wide distribu-
tion, as well as the ability to cope with the longer dry seasons or winters of the north.
In Africa, H. erectus soon outcompeted Australopithecus, which was extinct by 1.3
Ma or so.

Tools made by H. erectus include handaxes, which are remarkably symmetrical,
implying a cognitive preconception of shape, as well as the possible use of projectiles
(O’Brien 1981). Handaxes may also have served as curated multi-purpose tools (Toth
& Schick 1993; Keeley & Toth 1981) or as well-shaped cores (Potts 1988). Other
tools include spheroids, which may have been projectiles or “bolas” (Willoughby
1985) or simply well-used hammerstones (Schick & Toth 1994). Stone transport at
Olduvai is now 8 km or more (Toth & Schick 1993). Bone residues imply hunting at
some sites such as Olorgesailie (Shipman er a/. 1981; but see also Binford 1985).°

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Some bones were heated to very high temperatures at Swartkrans (1.3 Ma) which
could indicate cooking or controlled use of fire (Brain & Sillen 1988). At Chesowanja
in Kenya, and possibly also at Koobi Fora, burned patches yielding a unique magnetic
signal also suggest controlled use of fire by humans at 1.3 Ma (Bellomo 1993, 1994).
Sites were located on stream channels and their margins away from lakes (Clark 1970;
Toth & Schick 1986, 1993). These could be living sites, although some have many
handaxes and spheroids and little else, while others have ordinary flakes. Similarly,
a much smaller number of lakeshore sites may contain (Clark e¢ al. 1994) or lack
(Potts 1994) handaxes. Binford has suggested functional or organizational differ-
ences; different tasks may have been carried out at different sites by males vs. females
(Binford 1987, 1989), while Potts has argued that the handaxe sites represent
evidence for caching stone for later use (Potts 1988).

Caves were occupied in later periods in South Africa (Mason 1988b) and China
(Wu & Olsen 1985), implying an ability to hold these successfully, at least intermit-
tently, against other large cave-dwelling mammals, possibly through use of fire (but
see Binford & Ho 1985; Binford & Stone 1986; James 1989). Even later H. erectus
tools in East Asia, however, appear relatively unspecialized (Schick 1994). This is a
semi-human way of life.

Homo sapiens

The next species commonly recognized in the Homo lineage 1s Homo sapiens
“archaic” or H. heidelbergensis (see Stringer, this volume). The oldest fossils referred
to this group derive from Africa before 500 Ka (Singer & Wymer 1968; Klein &
Cruz-Uribe 1991; Clark er al. 1994), although some European fossils of possible
sapiens affinity may be as old (Bahn 1996; Carbonell ef a/. 1995). This is a very
poorly defined species boundary in terms of behavior shifts. In behavioral morphol-
ogy, the brain size increases ca. 33-50%, but the cranial shape, while higher and fuller
in the fronto-parietal region, is often broadly similar to that of H. erectus. Body size
does not increase. Somewhat greater flexion of the cranial base in “archaic” H.
sapiens may change the shape of the vocal tract, making speech slightly easier
(Laitman et a/. 1979; Lieberman 1984).

Neandertals are often considered as a specialized offshoot of the archaic group:
Homo sapiens neanderthalensis. Their morphology is characterized by an increase
in body mass, joint surfaces, and muscle markings (Trinkaus 1983a, 1983b, 1986),
and by a decrease in distal limb segments relative to proximal ones (Holliday &
Trinkaus 1991; Ruff 1991). These imply a physical response to ice age scarcity and
greater torsional strength of limbs, feet, arms, and hands (Trinkaus et al. 1994).
Neandertals may have been the first hominids to occupy Europe successfully through-
out a pleniglacial, beginning with a cold phase ca. 190 Ka (Tuffreau & Somme 1988).
Other peculiarities of Neandertals include possibly a different body stance suggested
by the Kebara pelvis (Rak & Arensberg 1987; Rak 1990), a high incidence of Harris’
lines and enamel hypoplasias (Ogilvie e¢ a/. 1989), which suggest stress during
growth (Skinner 1989), and little or no wear on the deciduous teeth which could

BEHAVIOR AND HUMAN EVOLUTION 145

indicate a long nursing period and slow population growth or a more rapid individual
transition from infancy to childhood than in ourselves. Neandertals also exhibit
maximum sexual dimorphism for Homo sapiens. This may imply a different, more
harem-like social organization as in the very dimorphic gorillas (Frayer & Wolpoff
1985; Binford 1989) or just greater selection for male effectiveness as providers.
Females may also have been more stressed during growth, and thus smaller in stature,
than in modern humans. Neither “archaic” H. sapiens generally, nor the more
specialized Neandertals, exhibit the specific characters of H. erectus such as the
supraorbital torus (continuous bar of bone over the eyes), sharp angle at the back of
the skull (inion), thick cranial bones, and the low cranial vault with maximum breadth
in the temporal region. Individually and collectively, however, “archaics” and H.
erectus fossils represent a continuum with much overlap in particular morphometric
traits.

Behavioral archaeology, for early “archaic” H. sapiens (e.g., Bodo, Petralona,
Ndutu) also suggests little difference from H. erectus. Tools are still characterized
by handaxe industries at sites such as Ndutu (Mturi 1976; Clarke 1990) and probably
also Bodo (Clark et al. 1994), and there is little regional differentiation in stone tools.
Sites include seasonally-reoccupied open-air sites as well as large mammal butchery
sites. Projectiles include wooden spears (Movius 1950). In textbooks, Torralba,
Ambrona (elephant butchery), and Terra Amata (open air “huts’) are still cited as
examples of H. erectus behavior, although fossils from nearby sites of comparable
age are all “archaic” H. sapiens (de Lumley 1969). Hunting may be more competent,
as suggested by evidence from the Spanish elephant sites (Villa 1990), but it is hard
to compare European sites with preceding African ones on this point due to different
availability of both scavengeable carcasses and prey.

The biggest behavioral differences between H. erectus and “archaic” H. sapiens
include the first intensive occupation of most of Europe by the latter (Delson 1991).
No undisputed fossils or human occupation sites on that continent are earlier than
600 Ka (Roebroeks 1994), with the possible exceptions of Vallonnet (de Lumley
1988) near Monaco (ca. 900 Ka, but with very dubious stone “tools”’), Isernia (ca.
730 Ka, but the dated tuff may be redeposited from an older context; Peretto 1991),
and, at Europe’s southeastern edge, a new Homo erectus jaw from Dmanisi (Dza-
paridze et al. 1992; Gabunia & Vekua 1995), in Georgia, possibly dating to 1.4-1.8
Ma.‘ Recently reported human remains from the Sierra de Atapuerca may date to ca.
800 Ka, but the hominids already exhibit derived features linking them with later
Neandertals (Carbonell ef al. 1995). H. sapiens may not have reached East Asia until
significantly later; sites containing remains of H. erectus occur in China as recently
as 300 Ka (Zhou & Ho 1990).

Additionally, in many “archaic” H. sapiens sites the advent of prepared-core
technology implies further cognitive imaging of the finished artifact. This technol-
ogy, however, is also found at several sites in association with late Homo erectus
(Leakey 1995; McBrearty 1990). A third possible trend is the occupation of more
caves and rock-shelters. A greater emphasis on smaller animals in some sites (Kalb
etal. 1982) may also imply more effective hunting techniques. However, changes in

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subsistence are very subtle; there is, for example, little exploitation of fish, shellfish,
or birds, and few small mammals. The latter may have been substantially removed
by carnivore scavenging, however, if hominids moved frequently enough (Yellen
1991). Evidence of symbolic behavior in early “archaics” is limited to possible
incisions or engravings on bone (Bordes 1972; Marshack 1989a; but see D’Errico &
Villa 1996) and to ocher lumps or “crayons”, faceted from use, by 300 Ka (Schmandt-
Besserat 1980; Marshack 1989a).

Again, Neandertals are a special case, as they are the only “archaics” who clearly
survive well into the time range of Homo sapiens sapiens (Léveque & Vandermeersch
1980; Straus 1994; Straus et al. 1993). At least some Neandertals appear to have
practiced cannibalism (Le Mort 1989; Defleur e¢ a/. 1993), while later Neandertals
buried their dead with grave goods (Solecki 1971, 1975; Smirnov 1989; Defleur 1993;
Hayden 1993; contra Gargett 1989). Neandertals used mineral pigments (Bordes
1972), cared for the sick and injured (Trinkaus 1983a), engaged in minimal long-dis-
tance trade of shells and stone, and made very occasional ornaments — an amulet
with a cross from Tata, a pierced fox canine from La Quina (Marshack 1989a).
However, all of these occurrences coincide with or post-date the appearance of these
behaviors in connection with modern humans at Qafzeh and Border Cave (Miller e¢
al. 1992; Valladas et a/. 1988; Schwarez et al. 1988). There are more behavioral
differences between early “archaics” and Neandertals than between early “archaics”
and H. erectus, perhaps justifying the recognition by some (e.g., Rak 1993; Stringer
1994) of H. neanderthalensis as a separate species of Homo. We recognize “human-
ness” in Neandertals, but it is curiously devoid of the rich symbolic aspects of modern
human cultures. Symbols of ethnic identity or of long-distance social networks are
absent. Even the linguistic competence of Neandertals is hotly debated, despite the
recent recovery of an anatomically “modern” hyoid with the Neandertal from Kebara
(Arensberg ef al. 1990).

Anatomically Modern Humans (Homo sapiens sapiens)

The final and current subspecies of Homo sapiens, although arguably as distinct
morphologically from Neandertals as the latter are from H. erectus, is also distinctive
in behavioral terms. This distinction is reflected in the literature as “the great leap
forward” of Diamond (1992), or the “Upper Paleolithic revolution” of Mellars and
others (1989, 1990). In behavioral morphology, the biggest differences include a
decrease in robusticity, longer distal limb segments, decrease in tooth size especially
in the anterior teeth, facial reduction, and increased basicranial flexion (Brace 1964,
1992; Laitman et a/. 1979; Lieberman 1984; Trinkaus 1989). All of these, particularly
when found in mid-latitude Europe, imply that cultural solutions replaced physical
adaptation in dealing with cold and scarcity. Other factors may also play a role:
reduced sexual dimorphism may imply a change in male-female relationships, a
decreased selection for male robusticity, or simply decreased stress on females during
their growth period. It is interesting also that in European specimens, Harris’ lines
and enamel hypoplasias decrease in early Homo sapiens sapiens compared to

BEHAVIOR AND HUMAN EVOLUTION 147

Neandertals, but wear on deciduous teeth increases, implying either slower growth
or earlier weaning and greater potential for population growth (Skinner 1989).
Among the “Cro-Magnons,”> we find the first “old” skeletons with the possible
exception of the old man from La Ferrassie (Trinkaus & Tompkins 1990; Trinkaus
1993), the only Neandertal known (or thought) to have reached the age of 50. In
addition to superior technology and social complexity, old age might be another factor
which increased survivorship of the young and thus the population growth potential
of H. s. sapiens in relation to Neandertals.

The oldest H. s. sapiens fossils, dating to 80-130 Ka, are found in Africa at the
sites of Klasies River Mouth, Border Cave, Equus Cave, Sea Harvest, and Die Kelders
in South Africa, Mumba in Tanzania, Omo (Kibish Formation) in Ethiopia, and
possibly Jebel Irhoud in Morocco (Brauer 1984; Beaumont 1980; Singer & Wymer
1982; Grine & Klein 1985, 1993; Miller et a/. 1992; Grine et al. 1991; Mehlman
1979, 1987; Hublin 1992; Brooks er al. 1993). These are followed closely by Qafzeh
in the Near East (Valladas er al. 1988; Schwarcz et al. 1988; Vandermeersch 1981),
although one could argue that Qafzeh was zoogeographically part of Africa at that
moment (Tchernov 1988). Some authors have argued, based primarily on the limb
bones from Klasies River Mouth, that these early specimens should be attributed to
an “archaic” H. sapiens group instead (Smith 1994; Holliday er a/. 1993). If the
Border Cave dates for the jaw (BC 5) and infant burial (BC 3) are sustained, however,
the evidence for gracilization in the face and cranium at an early date seems
indisputable (Miller ez a/. 1992).

The behavioral archaeology of H. s. sapiens suggests major shifts in human
adaptation in five spheres:

1. Distribution: Anatomically modern humans first appear in Africa and the Levant,

then in East Asia and Australia (Jones 1992), and finally in Europe and Siberia by just

before ca. 40 Ka (Hoffecker et al. 1993; Goebel et a/. 1993). Apparently the modern
human form could not or did not dominate or replace the Neandertal one until many
thousands of years after the first appearance of the former. Apparently, modern humans
also were the first human occupants of high latitudes (north European Plain, eastern

Siberia) by 20 Ka, and possibly also of the tropical forest (Bailey ef al. 1989; Brooks
& Robertshaw 1990).

2. Tools: Modern humans are characterized by new technologies—blades, burins,
backed pieces, bone tools, hafting, and projectiles such as spears, atlatls, harpoons, and
the bow and arrow (Petersen et a/. 1993). Raw materials may come from more than 100
miles away (White 1990) and be derived from specialized production or mining. There
is more specialized use of fire to heat-treat stone, make fired clay, or process pigments
for painting (Vandiver ef al. 1989). Boats, although not recovered directly in the
archaeological record, were probably what allowed dispersal to islands and island
continents (Allen et al. 1988; Jones 1992).

3. Diet: Faunal remains of single species, in a limited season, with prime age animals
dominating, suggest more ability to plan ahead and procure particular animals by
intercept or ambush hunting (Stiner 1991, 1994; Kuhn & Stiner 1994). More dangerous
animals were hunted (Klein 1978, 1989). Evidence also exists for trapping (warthogs,
boars, or hares), fishing, and netting (birds), as well as for seasonal consumption of
resources such as snails, seabird eggs, and seal pups (Troeng 1993). There is less
carnivore overlay on the faunal remains, implying longer occupation of sites (Kuhn &
Stiner 1994). The greater frequency of small animals in the African record may also
imply longer occupation of sites, as these tend to be completely consumed by animal
scavengers if fresh when the humans leave (Yellen 1991).

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4. Social organization: Modern humans clearly had larger, more complex social ties,
indicated by regional differentiation in stone tool styles, long distance trade, use of
ornaments to indicate status, and differences in status and wealth by 20 Ka (Soffer 1985,
1992). Artistic and decorative traditions develop (Marshack 1989a, 1989b). All these
may have related to the development of social networks as answers to risk and scarcity
(Wiessner 1983, 1984). The elaboration of social status differences appears greatest in
the coldest regions (Russia, Siberia), where risk and scarcity are greatest.

5. Symbolic behavior: This is exhibited in art, beads, and pendants, and in decoration

of both rock walls and utilitarian objects (Bednarik 1992), Notched and engraved pieces

suggest the beginnings of notation and even mathematics (Marshack 1989a, 1989b; de

Heinzelin 1961; Brooks & Smith 1987). The iconic or “isochrestic” value of style may

serve to link much larger social entities as well as to establish their frontiers against the

incursions of others (Hodder 1985; Sackett 1980, 1982). Their presence may thus imply
the existence of such large-scale groups, whose members may meet one another as rarely

as once ina lifetime if at all. In addition, as in Australian aboriginal painting and carving,

images may encode group experiences and serve as maps of space, time, and lifeways,

outliving the memory of any one individual. Such long-term memories may be particu-
larly valuable during the one year in a century when the reindeer or the rains do not
arrive.

Do the behavioral and morphological transitions to anatomically modern Homo
occur at the same time? Although this appeared to be the case in Europe, the evidence
from the Near East and Africa suggested that these transitions did not coincide (Clark
1988, 1992). In recent scenarios modern humans were thought to have appeared but
to have lived very much like Neandertals until they developed enough technological
expertise and social and symbolic elaboration to take Europe from the Neandertals
(Klein 1989, 1995). Now, more and more evidence from Africa suggests that the
“revolution” began there about when modern humans did, or not long thereafter. By
80 Ka technologies included blades (Clark 1988; Phillipson 1993), hafted projectiles
(Brooks & Yellen 1987), and bone tools (Volman 1984; Brooks er al. 1995; Yellen
etal. 1995). Economies involved fishing and seasonally-specific ambush hunting of
dangerous animals, e.g. warthogs and giant buffalo (Brooks et a/. 1980; Brooks et al.
1995: Yellen ef al. 1995; Wendorf er a/. 1993), as well as long distance procurement
of raw materials (Vermeersch 1990; Beaumont 1973, 1992; Merrick & Brown 1984;
Merrick ef a/. 1994), Seasonal hunting may also occur at Qafzeh (Lieberman 1993;
Lieberman & Shea 1994). In Africa, social networks are suggested by regional
differences in projectile style (Clark 1988) and by movement of raw materials
(Ambrose & Lorenz 1990), while incipient symbolic behavior is revealed in the few
ornaments (e.g., the Conus shell in the Border Cave burial), and decorated items such
as the incised ostrich eggshells from Apollo 11, Namibia and Diepkloof, South Africa
(Beaumont 1992), as well as by ground and processed pigments in a number of sites
such as # Gi and Kalkbank (Brooks & Yellen 1987; Mason 1988a). The oldest
representative paintings, however, appear much later, in the same general time range
as those of western Europe and Australia (Wendt 1972).

Symbolic activities begin to expand at ca. 50 Ka, just before the first appearance
of modern humans in Europe. We now have ostrich eggshell beads from several sites
in this time range in central/eastern Africa such as Enkapune ya Muto (Ambrose
1994) and Mumba (Hare er al. 1993), as well as possibly in southern Africa at
Bushman Rock shelter, Cave of Hearths, and Border Cave (Wadley 1993). A major

BEHAVIOR AND HUMAN EVOLUTION 149

change in technology also takes place at or before 50 Ka in at least some regions of
Africa, with the introduction of microlithic and small bipolar technology. This must
have involved composite tools such as arrows or drills (Van Noten 1977; Brooks &
Robertshaw 1990; Mehlman & Brooks 1992; Deacon & Geleijnse 1988). The first
“Upper Paleolithic” of both North Africa and Near East, just before 40 Ka, also
involves small bladelets, not large crude blades, steep scrapers, and bone points as in
Europe (Bar-Yosef 1994). Travel to Australia at or before this time implies the
existence of boats (Roberts et al. 1990). The last 20,000 years are characterized by
increasing manipulation of the environment itself through burning and possible herd
management, long before actual domestication and agriculture (Mellars 1976).

Continuity or Replacement?

Can archaeology tell us about how and why moderns replaced Neandertals?
“Why” is easier than “how”. Moderns may have had shorter birth intervals and better
assurance of survivorship by “grandparents” as well as by survival of parents into
their children’s adulthood. Moderns also exhibited better hunting techniques, alter-
native food sources (fish, snails), broad social networks and the ability to interact
over long distances, increasing their chances of finding enough to eat if the local
resources failed. Whether these new behaviors were the consequence or the cause of
biological gracilization and brain evolution is as yet unclear. The new African
evidence suggests that the “great leap forward” may actually consist of a number of
crabwise steps, coinciding with a mosaic and gradual achievement of anatomical
modernity.

“How” the change occurred, whether by replacement or by continuous change in
each region, is even harder to determine (Smith 1992; Aiello 1993). The replacement
theory implies the existence of a species boundary between Neandertals and modern
humans which did not permit genetic mixing. In our behaviorist model, this theory
also demands a strong association between modern behavior and morphology vs.
archaic behavior and morphology, at least for the last 50-60 k.y. Some aspects of
modern human culture, however, were shared with Neandertals by as early as 55 Ka
(Léveque et al. 1993; Kuhn 1995; Stiner 1994; Kuhn & Stiner 1994; Gamble 1994),
implying either parallel development or behavioral diffusion across subspecies or
species boundaries. And early modern culture, when it appears in the Neandertal
regions, is very different from what we find in Africa. Indeed, this early European
modern culture (the Aurignacian) appears in Europe as much as 6,000 years before
we find it in the Near East (Bar-Yosef 1992; Bar-Yosef & Belfer-Cohen 1993, in
press; Bar-Yosef et al. 1996). Fossils associated with these earliest Aurignacian
assemblages are few and fragmentary, so that at the very least the association in
Europe between the appearance of modern humans and that of modern human
behavior is undocumented. On the one hand, distal limb segments of the early
moderns in Europe are long, relative to proximal limb segments, implying a tropical
origin according to Allen’s Rule (Trinkaus 1981). On the other hand, at Vindija
(Wolpoff et al. 1981; Smith & Ahern 1994) fragmentary cranial remains from the

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earliest Aurignacian assemblage have been assigned to H. s. neanderthalensis!
Although most archaics exhibit different behaviors from most moderns, the evidence
for sharp behavioral discontinuities at the temporal species boundary 1s ambiguous.

While the African record implies the earlier evolution of anatomically and
behaviorally modern humans from archaic antecedents on that continent, setting the
stage for the replacement scenario, the European record suggests that modern
Europeans evolved there behaviorally from more archaic antecedents, whether
indigenous or not. This transformation could have taken place as an entirely indige-
nous Neandertal development, a local translation of borrowed ideas about projectiles,
hunting, and risk avoidance, which dramatically reduced the selection for robusticity
(Brace 1992). Given the morphological discontinuity between Neandertals and early
moderns, however, a more likely process might have involved local cultural evolution
by a small group of anatomically modern Homo sapiens who made it into Europe,
presumably from the Near East, around 55 Ka, before the Upper Paleolithic “revolu-
tion” (see Gamble 1994). Arriving in eastern Europe, this small group may have
borrowed some ice-age adaptations from the Neandertals, possibly interbred with
them to some degree, and developed rapidly in isolation to the point where they wiped
out or outcompeted the Neandertals. In any case, the possibility of a major migration
from Africa to Europe at 40 Ka finds little support in the archaeological record."

A cautionary tale, however, is provided by the widespread appearance of anatomi-
cally modern humans in North America around 12 Ka (e.g., Frison 1993). Here the
derivation from northeast Asia is very clear on the basis of dental and other mor-
phologies (Turner 1983, 1986, 1989), but obscure archaeologically since the Clovis
projectile point tradition has no Siberian counterpart (Goebel ef a/. 1993; Goebel &
Aksenov 1995). There is, however, very sparse and scattered evidence, particularly
in Alaska, of an older, less specialized, pre-Clovis industry (Goebel e7 a/. 1991;
Hoffecker et al. 1993) with parallels in Asia. Colonization of a new environment may
be in itself as strong an impetus to cultural innovation as it is to morphological
diversification or adaptive radiation and demic expansion. However, in the behavioral
record conservative traits, analogous to dental cusp and enamel patterns which point
to ancestral relationships, are either absent or undefined in our current methodologies.

Behavior and Morphology in Human Evolution

In summary, the record of human behavioral evolution has been much enriched
by new types of study: of raw material sources, use-wear, bone breakage, seasonality
of prey death, and regional site structure, as well as from an integration of behavioral
morphology and archaeology. The fossils and the archaeology together suggest three
major behavioral shifts: (1) the first appearance of sites and tools at ca. 2.5-2.1 Ma;
(2) the emergence of more human patterns of growth, care of adolescents, meat-pro-
curement, hunting, use of fire, and niche expansion to Asia at ca. 1.6-1.4 Ma; (3) the
emergence ofa fully human way of life involving technological innovation, complex
social networks, think-ahead hunting and general long-range planning and procure-
ment, symbolic expression, and worldwide niche expansion between 100 and 40 Ka.

BEHAVIOR AND HUMAN EVOLUTION 15]

TABLE 4. Species Boundaries in the Lineage of Homo

Discontinuity with Predecessor

Species Morphological Behavioral
H. habilis +42(2) ++ (?)
H. erectus ++ ara

H. sapiens (archaic) +(?) 2?

H. sapiens sapiens nL A+

While there are also three generally recognized species of Homo, only two of these
behavioral shifts correspond to possible species boundaries (Table 4). A major
species boundary (H. erectus/H. sapiens) involves little recognizable change in
behavior other than habitat expansion to Europe, while the major behavioral change,
in current thinking, involves a subspecies rather than a species boundary. This
discrepancy suggests the need for taxonomic revision in later hominid evolution, as
well as for new approaches to understanding human behavioral change.

Endnotes

1. “To these anatomical traits [of Homo habilis| could be added the very strong evidence
that was emerging from M. D. Leakey’s careful excavation of occupation floors at Olduvai,
that the Olduvai gracile hominids were the makers of the tools of the Oldowan industry . . .
Since no convincing associations of stone artefacts with australopithecines were known, such
lithocultural activities, it seemed to Napier and myself (1964), provided powerful ethological
evidence, supportive of the probable presence of Homo” .. . “Our importing of the cultural
evidence more strongly into the scale pans in weighing up the generic status of Homo habilis
was entirely in keeping with accepted procedure that ethological evidence may be added to
morphological evidence in the assessment of the systematic status of a group.” (Tobias
1991:30, 38)

2. Recently, Wood (1984, 1991, 1992a, 1992b, 1993, and this volume), and Turner and
Chamberlain (1989) have proposed to recognize several new species of the genus Homo, based
on morphological variation. Specimens grouped by Tobias (1991) within 7. habilis are divided
into H. habilis and H. sp. nov. or H. rudolfensis, while some specimens of what was formerly
recognized as African Homo erectus are placed in another species, H. ergaster. Cultural or
behavioral differences between H. habilis and H. rudolfensis have not been documented.
Similarly, no clear behavioral differences exist between H. erectus and H. ergaster. For the
purposes of this paper, therefore, H. habilis and H. erectus may be regarded as single taxa,
which may have included separate morphotypes sharing similar behaviors. Indeed until
behavioral or ecological differences between the included morphotypes are demonstrated, the
argument for according these morphotypes the status of separate species is in question (see
discussion of “archaic” H. sapiens, below).

3. Note, however, that the sites most often cited in textbooks as examples of Homo erectus
hunting behavior, Torralba and Ambrona in Spain, are too late in the Pleistocene for Homo
erectus, at least in Europe, and probably include the activity residues of some form of archaic
Homo sapiens.

4. Geographically this site is better seen as an extension of the Near East, rather than as
evidence for early settlement of the European landmass. The date derives from a normally-po-

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larized underlying tuff dated to 1.6-1.8 Ma; the interval between deposition of the tuff and
deposition of the jaw, however, is uncertain. Photographs of the excavation suggest the possible
presence of soil horizons and/or unconformities between the tuff and the jaw; these suggest
the need for further geological and geomorphological inquiry at this important site.

5. This name derives from a group of fossils of modern but robust type excavated in the
nineteenth century by Lartet and Christy from a rock-shelter in Les Eyzies, France. The
stratigraphy of this excavation was poorly controlled, the deposits were entirely removed, and
the site is now occupied by a hotel. Both the recovered artifacts and the very careful excavation
during 1953-1964 of the Pataud site, a few hundred yards to the west, suggest that the
Cro-Magnon site may have conserved evidence from almost the entire range of the early Upper
Paleolithic (ca. 34,000-21,000 BP). Attribution of the fossils to the earliest levels, or more
specifically to one of the later Aurignacian horizons, is on the basis of the excavation
description and associated artifacts which contained no Gravettian forms (Movius 1971, 1995).

6. North Africa outside the Nile Valley appears less likely as a direct staging point for the
first incursions into Europe by anatomically modern humans. Much of North Africa was very
sparsely settled prior to 40 Ka (Wendorf eg al. 1993), and the distinctive Aterian projectile
points and tanged scrapers of the North African Middle Stone Age have no counterparts in
Europe. Neither Sicily nor southern Spain, two of the more logical points for such a crossing,
have particularly early manifestations of the Upper Paleolithic. The last Mousterian sites of
southern Spain are almost 15,000 years later than the earliest Aurignacian sites of eastern
Europe (Straus 1994; Straus er a/. 1993).

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167

Molecular Anthropology in
Retrospect and Prospect

Jonathan Marks
Department of Anthropology
Yale University

New Haven, CT 06511

The application of molecular genetic data to anthropological questions has a
long history. These data, like any data, only make sense as they are integrated into
the existing corpus of data and theory. Our cultural prejudice about the primacy
of heredity in human affairs has sometimes allowed studies based on genetic data
to gain more credibility than they merit from methodological, analytical, and
theoretical standpoints. Ultimately molecular data augment, but do not supersede,
more traditional methods of anthropological inquiry.

I think we are all in fundamental agreement about the utility of molecular data in
augmenting the more traditional modes of scientific inference about human origins.
Genetic data provide for us an independent test of phylogenetic hypotheses; inde-
pendent, that is, of the morphological, anatomical data with which macrobiologists
generally work and on the basis of which they have been eminently successful in
reconstructing the history of life.

Occasionally, however, there is a specific phylogenetic problem that appears to
be intractable. Perhaps the species have adapted to radically different environments,
concealing much of their shared ancestry; or perhaps several species all appear to be
equally different from one another. In such cases, genetic data can be helpful,
providing a suite of characteristics — the nucleotides that compose DNA, or some
estimator of them — that do not directly interact with the environment themselves,
and therefore will be less subject to convergent evolution than anatomical traits.

Often, however, we expect more from genetic data in the arena of anthropological
systematics. It is not simply that we have another set of data that transcends the main
problems in the data we are accustomed to. Rather, there is the expectation that in
the genetic data we have something truer and more scientifically valid, something
encoding actual history so purely that all you have to do is put on the right pair of
glasses and read it.

I will argue in this paper that the right pair of glasses are rose colored, and that

Contemporary Issues in Human Evolution Memoir 21, Copynght © 1996
Editors, W.E. Meikle, F.C. Howell, & N. G. Jablonski California Academy of Sciences

168 MARKS

our attitude toward genetic studies in anthropology is far more deeply rooted in our
cultural values than in any significant aspects of genetic data themselves. It lies in
the Euro-American tradition that “blood will tell,” which is still with us socially and
scientifically. Science paperbacks, and some scientists themselves, now assert that
deriving the sequence of the DNA ofa single composite human cell — a genome —
will cure cancer (Dulbecco 1986) and social problems like homelessness (Koshland
1989) and reveal ultimate insights into the human condition (Watson 1990). Indeed,
the goal of sequencing a single human genome has become largely synonymous with
the research enterprise of human molecular genetics (Olson 1993).

Now, | would not use genetic methodologies in my own research if I did not think
them worthwhile. The criticism I will raise — the set of cultural values of which I
speak — is very specifically in the taking of genetic data uncritically as authoritative.
Introspective anthropologists have shown that we generally project our cultural
values and expectations onto the data of paleoanthropology and primate behavior, in
order to come up with an explanatory narrative of human evolution. But somehow,
genetic data are above all that: they involve fancy equipment and computers, and we
have come to expect that they tell a story almost independently of such mundane
considerations as the assumptions, data analysis, experimental design, or theoretical
basis for interpreting the results.

Yet historically there are myriad examples of how genetic work has been loaded
with cultural values and has guided us to wrong-headed conclusions (Nelkin &
Lindee 1995). In 1924, for example, every textbook of genetics discussed the topic
of eugenics favorably, and every geneticist of note in America advocated that
program (Marks 1993b). This was the program that held most of the world’s
populations to be constitutionally degraded, possessing a recessive allele for feeble-
mindedness. Therefore, the solution to urban social problems was to discourage
immigrants from breeding and to prevent more immigrants from entering. It provided
the scientific validation for the Johnson Immigration Restriction Act of 1924.

Nowadays, we have the disputes over DNA fingerprinting, which had been used
to bully juries intellectually until 1989, when a couple of clever lawyers actually had
other geneticists examine the raw genetic data constituting the scientific validation
for the state’s case. They found the controls to be inadequate, the experiments
shabbily conducted, and they began to raise basic questions about the validity of
conclusions drawn from such work, questions that have not yet been satisfactorily
resolved (Billings 1992).

From the standpoint of human origins, however, the controversies surrounding
DNA fingerprinting or an egregious social program like eugenics are about heredity
per se, but not really about systematics. I introduce them to illustrate the fact that
genetic data are fallible; or more specifically, interpretations of genetic data are
fallible. This has direct relevance for anthropological systematics.

Genetics in Racial Anthropology

Physical anthropology in pre-1960 days centered around the question of identify-

MOLECULAR ANTHROPOLOGY 169

ing the single-digit number of basic forms into which the human species could be
subdivided. These forms, of course, were called races, and their differences were
thought to be the source of the bulk of the hereditary variation in Homo sapiens.
Fieldwork led anthropologists to the conclusion that races were themselves exceed-
ingly heterogeneous; studies of immigrants showed that much of the anatomy that
had been considered fundamentally racial, such as head shape and other aspects of
body form, was in fact strongly influenced by the environment.

The alarm call in racial studies was answered by the study of blood. Blood, of
course, is a dominant metaphor for heredity, and in this case one could study the blood
groups of different peoples and compare them over one tiny portion of their hereditary
makeup.

Now, let us cheat a bit. There are three major alleles, A, B, and O, and pretty much
all populations have all three alleles. Geneticists call this a polymorphism (Table 1).
In fact, that is paradigmatic for the study of human genetic variation: nearly all
populations have nearly all alleles. Virtually everywhere, O is the most common
allele. A is very common in all populations, except among Native Americans. B is
uncommon in all populations, but more common among Asians than among most
others. Some Native American groups seem to have lost both the A and B alleles,
being almost totally O. The differences we encounter among ABO frequencies across
populations are intergrading, not discrete, and it seems unreasonable to expect that
they would shed much light on the discrete differences that anthropologists wished
to identify as being racial.

Nevertheless they did, according to geneticists of the 1920s and 1930s. The initial
ABO frequency data collected by Hirschfeld and Hirschfeld (1919) during World
War I managed to divide populations into three categories: European, Asio-A frican,
and Intermediate. In other words, it partitioned the human species pretty nicely into
“white” and “other.” Since the ABO blood group says nothing of the sort nowadays,

TABLE |. ABO Allele Frequencies from Representative Populations.
Taken from Mourant et al. (1976)

———_—_—— Allele Frequency— : —

Aboriginal Population A B O
America Chippewa .06 00 94
Kwakiutl 10 00 90
Europe Denmark 27 08 66
Bulgaria 31 12 56
Ukraine ZU 16 57
Asia Kazakhstan 25) a2, 48
Pakistan .20 25) 55
Japan 29. 16 54
Oceania Australia 18 04 78
Africa Efe Pygmies 26 21 53
Angola 16 11 72

Sierra Leone. 16 =) Ie) 69

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it stands to reason that those conclusions tell us more about the researchers’ mindset
than it does about genetics.

But that was not all, for there was prehistory to reconstruct. The presence of three
diagnosably different kinds of blood substances (A, B, and O) made it, in the words
of those researchers, “very difficult to imagine one single place of origin for the
human race” (Hirschfeld & Hirschfeld 1919:679). Consequently, they proposed an
ancestral “O” human species, subsequently invaded by “two different biochemical
races which arose in different places” (ibid.). In other words, polymorphism and
heterozygosity were the result exclusively of racial invasions.

Encountering almost wholly type-O blood in the New World led genetic serolo-
gists a few years later to the conclusion that Native Americans diverged from the rest
of humanity early on, before the invasions of the A and B people in Europe, Asia,
and Africa and the differentiation of those populations from one another (Coca &
Diebert 1923). That this interpretation agreed with virtually nothing from the field of
anthropology did not seem to matter.

In 1925 and 1926 the blood group serologists, apparently dissatisfied with the
“white/other” classification, used ABO to divide humanity into seven “types”:
European, Intermediate, Hunan, Indo-Manchurian, Africo-Malaysian, Pacific-
American, and Australian (Ottenberg 1925; Snyder 1926). These were at some
variance from the groups anthropologists tended to see when they divided up the
human species, but this was genetic data, and there seemed no good reason even to
try to reconcile it to anthropology.

Actually, however, there was no real division of these types strictly on the basis
of their ABO allele frequencies. What the researchers had done was just basically to
divide the world’s populations into large para-continental groups, impose the ABO
data upon them, and describe the results. Consequently, several populations assigned
to one “type” actually had ABO frequencies that fell within the ranges of other human
“types.” Conversely, in some cases diverse people happened to have too similar a
distribution of alleles. This produced a number of inconsistencies. For example, the
people of Senegal, Vietnam, and New Guinea ended up together. Likewise did the
people of Poland and China. America’s leading physical anthropologist, Harvard’s
Earnest Hooton, whose interest lay in isolating pure racial (pheno)types, felt that any
method that put together such a motley group of people was basically worthless
(1931:490).

By 1930, serologist Laurence Snyder had abandoned the seven race-type system,
but still argued “forcibly [for] the value of the blood groups as additional criteria of
race-classification” (1930:132). Snyder now had the peoples of the world carved up
into 25 (unnamed) clusters, based on different criteria than anthropologists used, but
harmonious to some extent and disharmonious to some extent. His prediction that "in
the future no anthropologic study will be complete without a knowledge of the blood
group proportions under discussion” (ibid.) could be considered optimistic, given the
specious reasoning and conclusions that had accompanied its use thus far. Indeed,
the fact that apes have ABO alleles, which strongly suggests that the polymorphism
is ancestral to the origin of the human species, was demonstrated in 1925, but the

MOLECULAR ANTHROPOLOGY 17]

population dynamics of a primitively polymorphic system does not seem to have been
invoked as an explanation for the ABO distribution in humans before William Boyd
(1940).

Where there was concordance between genetic and phenotypic analyses, obvi-
ously no difficulties arose. Where there was discordance, however, the assumption
that results derived from the blood must be fundamentally more reliable, no matter
how they were generated or how poorly understood they were, remained a justifica-
tion for using the serological data to carve up the human species. It took decades of
mulling over these data to appreciate the basic nature of the patterns being encoun-
tered in the human species. And the basic pattern was what only Hooton recognized:
if you were interested in establishing discrete phenotypic groups of people, the
genetic data were pretty much irrelevant.

Ultimately, the major original contribution of serological data in racial anthropol-
ogy was to promote the Basque people of the Pyrenees of Spain to a separate race,
equivalent to “Africans” or “American Indians” (Boyd 1950:268). Of course, it’s not
as if they had green skin and square heads; they simply speak a strange language and,
more importantly, have allele frequencies somewhat different from their neighbors.
And that is enough, if you believe in the existence of discrete races and in the power
of genetics — just a little bit of genetics — to reveal them.

So the study of blood group genetics, cited since the early 1970s as undermining
the concept of race, was consistently interpreted within it, and certainly as supporting
it. The races revealed were sometimes concordant with traditional anthropological
ones (especially when the genetic data were largely imposed on geography); when
they were discordant, the genetic data were assumed to be simply better. There were
no good scientific reasons for this, just good old cultural ones.

Probably the most interesting claim for the hereditary study of our species was
published in the American Journal of Physical Anthropology in 1927 by a Russian
named Manoilov, who reported that a series of simple chemicals added to a sample
could distinguish Russian blood from Jewish blood. Following this, Poliakowa
(1927) reported that Manoilov’s test permitted her to distinguish among the bloods
of various Euro-Asian countries. The test turned the blood of Russians reddish, of
Jews blue-greenish, and of various other peoples various other colors. Again, Amer-
ica’s leading student of human diversity as race, Earnest Hooton, found this claim
difficult to swallow (1931:491).

In other words, this study of “blood” — again, a dominant metaphor for “heredity”
— was producing conclusions at considerable variance with what anthropologists
already knew. Races, whatever they were, were certainly not the same as nations, and
it was hard to believe that they would each have diagnosably different blood
structures. The notable aspect of this critique is that it is not based on any methodo-
logical flaw in the work, but simply on the conclusions, which could only have been
a reflection of the investigators’ prejudices or expectations. The work of the Russian
hematologists was rejectable because in their ignorance they failed to appreciate that
known patterns of human variation invalidated their work a priori; in their arrogance,
they thought they were going to revolutionize anthropology with it. The work was

172 MARKS

scientific, it involved strict hereditary factors, it was reviewed and published, and it
came to foolish conclusions that were dismissible independently of the allure of the
hereditary substance they studied.

Ina follow-up publication also in the American Journal of Physical Anthropology,
Manoilov (1929) reported the ability to distinguish the blood of men from women,
and discussed a colleague whose application of these techniques could distinguish
the blood of homosexuals from heterosexuals. And it worked just as well on plants,
in spite of the biological difficulty posed by extracting blood from them. | would
suggest that if these workers had made identically idiotic claims from measuring the
width of the shoulder blade, their manuscripts would never have made it past the
secretary’s desk. The fact that they were studying blood, the fact that they were
studying deep heredity, gave their work greater power and validation than it actually
merited.

Manoilov’s work was far from obscure, for it was discussed at the highest levels
in the genetics community — by T. H. Morgan and C. B. Davenport — and was the
subject of several publications in Science and the Proceedings of the National
Academy of Sciences. It also found its way into genetics textbooks of the era (Schull
1931; Sinnott & Dunn 1932). Interest among the cognoscenti had begun to wane after
a biochemist reported privately that Manoilov’s blood test did not actually even
require blood; it worked just as well on urine (K. George Falk to C. B. Davenport, 9
December 1926, C. B. Davenport Papers, American Philosophical Society). To this
day we do not know what the test was actually testing — quite possibly a figment of
geneticists’ imaginations, yielding essentialized differences among groups presumed
to be essentially different.

The Trichotomy: Molecular Anthropology’s Gordian Knot

The undisputed triumph of molecular work in anthropological systematics was
Morris Goodman’s demonstration (1962) that humans and chimpanzees and gorillas
were more closely related to each other than any was to an orangutan. Not only that,
but genetically — if no other way — humans, chimpanzees, and gorillas were virtu-
ally indistinguishable from one another. They appeared to form a genetic
“trichotomy.” (The de-hominization of the fossil taxon Ramapithecus (Sarich &
Wilson 1967), often hailed as a triumph of molecular systematics in anthropology
(e.g., Lewin 1987), was actually a dispute over rates of molecular evolution, and its
implications for systematics were thus indirect. Nevertheless, for those with a short
memory, it seemed to bring the score to Molecules 1, Morphology 0.)

In the 1980s, however, it emerged as threatening that the ostensibly potent
molecular data were apparently unable to resolve this three-way split into two
sequential two-way splits. An extraordinary amount of effort has been thrown into
the question of genetically resolving this trichotomy — as if a three-way split were
impossible, and as if genetic data, like the Delphic Oracle, must be capable of
answering all questions put to them.

The gross comparison of ape DNA, by DNA hybridization, shows a three-way

MOLECULAR ANTHROPOLOGY 173

TABLE 2. DNA hybridization values from two studies, mean distances and
standard deviations. Column (A) is the numbers given by Sibley ef al.
(1990), without the impermissible data alterations used, and not reported,
in their prior publications. Column (B) is calculated from the Appendix to
Caccone & Powell (1989), without the alteration based on the indefensibly
precise measurement of DNA fragment length. These are the most
comparable sets of numbers; see Marks (1991).

Unaltered ATm Values

(A) (B)
Human-Chimpanzee 1.4+.8 2441.1
Chimpanzee-Gorilla Lic: 4 3.0+ 6
Human-Gorilla 1.8+.8 4141.1

split, with large error margins (Table 2). This technique, it turns out, only resolves
the trichotomy when you tinker with the numbers; for example, by substituting
controls across experiments, or moving correlated points into a regression line (Sibley
etal. 1990), or precisely changing the measured values on the basis of a DNA smear
from which the DNA fragment length is precisely extracted to the nearest single
nucleotide (Caccone & Powell 1989), which users of this technique admit they did
(Marks 1991). The fact is you could resolve anything with any set of data if taking
such liberties were legitimate. It is not, and general interest and use of this technique
has precipitously declined on that basis. That a few zealots still defend it (Lowenstein
1993; Ruvolo 1995) actually speaks more to sociology-of-science than to molecular
anthropology. At best, the work represented the Manoilov blood test of the 1980s.

DNA sequencing studies fall fairly neatly into two categories. The first comprises
those in which the split is too close to call, and its resolution depends heavily on the
method of outgroup rooting and clustering technique. The second category comprises
those in which a specific pairwise linkage is argued to be favored, contradicting other
data sets in which a different pairwise linkage is favored (Marks 1992).

This raises fascinating questions about the epistemology of molecular evolution.
For example, although three data sets of mitochondrial DNA fall into the first
category (Ferris e¢ a/. 1980; Brown et al. 1982; Hixson & Brown 1986), a fourth was
claimed to have resolved the trichotomy into human-chimpanzee (Horai e¢ a/. 1992).
The reasoning is simple: these 4900 bases yield approximately 180 phylogenetically
informative nucleotide sites (i.e., those in which two character states are found across
human, chimpanzee, and gorilla, and one of them is also in the outgroup, the
orangutan). Approximately 85 of these link human-chimpanzee, 55 link chimpanzee-
gorilla, and 40 link human-gorilla. Since the favored pairing here is human-chimpan-
zee, the link is taken as proved.

But evolutionary history is not like a Democratic primary in which the candidate
with the plurality of votes wins. For if those 85 bits of data are giving the “right”
answer, then the 95 other bits of data (55 + 40) in that same set are giving the “wrong”
answer. The argument for human-chimpanzee, then, boils down to accepting 47% of

174 MARKS

the informative data, and rejecting 53%. Seen this way, it does not constitute a
particularly strong scientific argument in favor of resolution of the trichotomy.

The key recognition here undermining the claim of “resolution” lies in considering
the efficiency of this molecular evolutionary system. To judge the phylogeny as
“resolved” implies that this system is inefficient, or un-parsimonious, enough to
generate 53% “wrong” answers, if we assume that the 47% showing human-chim-
panzee are “right.” But paradoxically, it also implies that this system is so efficient
that it could not be generating 70% “wrong” answers and only 30% “right” answers
(i.e., if chimpanzee-gorilla were “right”). In other words, the assumption is that this
system is maximally parsimonious, although it is obviously not very parsimonious at
all.

In my opinion the best interpretation is actually neither of these. Rather, it 1s that
these data reinforce the trichotomous nature of the relations among these three
lineages. If it were indeed the case that the late Miocene stem lineage effectively split
simultaneously into three lines, we would expect those 180 informative sites to
distribute themselves as about 60-60-60 in favor of each of the three pairwise
linkages, and thus only 25 of them, or 14%, are “wrong.”

The second category, datasets pointing one way and contradicted by others
pointing a different way, represents much of the DNA data from the nucleus (Marks
1992). Most of our data here come from the beta-globin cluster, of which bits and
pieces have told various stories at various times (Miyamoto & Goodman 1990),
although generally tending to point to human-chimpanzee (Bailey er a/. 1991). The
gene fora skin protein called involucrin seems to link chimpanzee and gorilla (Djian
& Green 1989). The immunoglobulin genes yield all three permutations (Ueda er al.
1985; Ueda et al. 1989; Kawamura et a/. 1991). Best of all, the little bit of DNA where
the X and Y chromosomes pair up, known as the pseudoautosomal region, slightly
favor chimpanzee-gorilla with the X, and chimpanzee-human with the Y (Ellis e¢ al.
1990).

The trouble here in gene-land is actually very fundamental. It is the absence of
population genetics, of a consideration for the processes of microevolution that might
impact upon the clarity of discernible macroevolutionary patterns (Rogers 1993) —
not terribly unlike the early racial serology.

In one of the most important, but unheralded, studies of recent years in molecular
anthropology, Ruano er al. (1992) actually looked at the extent of within-species
diversity in the apes, in relation to the phylogenetic information extractable from the
DNA sequence they were studying. They looked at a stretch of a couple of hundred
nucleotides from the homeobox cluster of chromosome 17. Finding it to be absolutely
invariant across a diverse sample of humans from all over the world, they then studied
16 homologous chimpanzee sequences and found two alleles, and twenty gorilla
sequences and found four alleles, one of which was very divergent (Figure 1). Their
important conclusion was that, despite a single DNA base difference superficially
linking the human to the two chimpanzee sequences, the amount of polymorphism
present, reflecting the breadth of the gene pool, swamps any attempt to extract a
reliable phylogenetic inference here.

MOLECULAR ANTHROPOLOGY 175

4
b sorilla |
w = (
<x i |
5 . o ? Orang
i) fae FUMAN te
> ae |
D
C3

<== Ulversity ==>
FIGURE |. Extensive diversity in African ape DNA, drawn from very heterogeneous gene
pools and undermining the prospects of “resolving the trichotomy” from single representatives
of each species.

There are two important theoretical reasons why polymorphism is necessary to
sample ina problem like this. The first involves the simple discordance between the
phylogenetic history of three species and of three DNA sequences when the three
DNA sequences are taken to represent the three taxa (Figure 2). If the dark allele
gives rise to the intermediate allele, and the intermediate allele to the light allele, and
all three co-exist in the ancestral species, they may segregate into descendant taxa in
a manner that reflects not the sequence of speciation events (or the species tree), but
only the descent of the DNA sequences from one another (or the gene tree). This can
hopefully be overcome by sequencing many unlinked loci, which would presumably
not all be segregating in such a fashion (Pamilo & Nei 1988).

The second problem is more formidable and stems from the fact that the budding

A B Cc

Species tree

(

—/
ee

B
oN oes
se

Gene tree

FIGURE 2. A gene tree might not replicate a species tree, due to the segregation of ancestral
polymorphism. See text for explanation. (After Marks 1992)

176 MARKS

of anew species from an old, speciation by the founder effect, which is probably very
common, results in paraphyly in the parent species. Paraphyly is a relationship
wherein all members of a biological group are not one another’s closest relatives,
because one or more that should be in there have been excluded.

In Figure 3, we have a cosmopolitan species, A, which varies genetically over a
geographical gradient, as any species in nature will. From some part of this species,
a new species, B, forms. B forms from members not just of species A, but from a
particular segment of species A, and then obtains its own biological identity. Species
A is now paraphyletic because, regardless of who can mate with whom, which ts
usually what we mean by species, species B is genetically more closely related to one
part of species A than two parts of species A are to one another. Now, species A and
species C are still one species. Species C forms some time later, from another segment
of species A. When we draw the relationships based on this simple history, we would
therefore draw it with A and C sharing a unique chunk of biological history, not shared
by B. Thus, A and C are closest relatives.

8 buds from A Parapnyly’ Some parts of species A are more closely
related to parts of species B
than to ther own species,
despite reproductive capabilities

A and nascent C share
history separate from 8

C buds from A

\ Ys Actual species
oe relationships

Noy
4

FIGURE 3. Founder effect speciation in a variable ancestral population produces paraphyly.

But if we try to reconstruct that history from a single piece of DNA from each
species —— no matter how much DNA — we run into a problem (Figure 4). If the
representative of species A that we choose is from the left, we may find B and C to
be closest relatives; if it is from the center, we may find A and B to be closest relatives.
We would really have to be lucky and choose a specimen from the right to come up
with the historically correct answer. In other words, you need several specimens of
species A in order to have any kind of a fair chance of reconstructing the biological
history of this group, and the chances of doing so will be affected by variables like

MOLECULAR ANTHROPOLOGY La

Apparent relationships
dependent upon sample used of species A

AZ ABC DC
[ED

FIGURE 4. Paraphyly produces phylogenetic ambiguities.

the time between the two divergences and the extent of gene flow within the parental
species.

We can add another fairly simple twist to this example. Say that species C is very
successful, out-competes part of species A, and expands its range at the expense of
species A (Figure 5). This could quite simply wipe out your chance of recovering the
correct relationships altogether. All the more reason why I would expect molecular
studies of the apes to understate the strength of their claims to have resolved the
trichotomy in the absence of information on intra-specific variation, but generally
they do not. There is, after all, something of a lack of humility often characterizing
molecular research generally. It feeds off our cultural values of what we think is
important and fundamental and revelatory — it is a glimpse of deep heredity, al-
though sometimes in the absence of a sound theoretical framework for understanding
or interpreting it.

It is of some interest in this regard that the sets of genetic data which have actually
attempted to sample intraspecific variation generally tend to link chimpanzee to
gorilla, in harmony with traditional interpretations of the anatomy. These are gener-
ally qualitative studies as well: the involucrin gene sequence (Djian & Green 1990);
the dark bands at the chromosome tips of chimpanzees and gorillas (Marks 1993a);
as well as other DNA sequences (Dangel et a/. 1995; Livak et al. 1995; Meyer et al.
1995). One quantitative study examining intraspecific variation and linking chim-
panzee to human has also been reported (Ruvolo 1994), but its proper interpretation
is unclear (Marks 1995a; Green & Djian 1995; Rogers & Comuzzie 1995). The
strongest molecular evidence in support of human-chimpanzee is from the hemoglo-

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li C competitively
Jl excludes A

Correct relationships
cannot be discerned

FIGURE 5. Under some simple circumstances phylogeny may not be accurately recoverable.
See text for discussion.

bin genes on chromosome 11, which is all-too-familiar to anthropologists as the site
of strong selection for genetic diversity leading to malaria resistance — although no
polymorphism has been sampled in the phylogenetic research here.

Paradoxically, in this arena the studies making the most extravagant claims often
emerge to have been based on the weakest data. One widely-publicized study claimed
“resolution” of the trichotomy based on 692 nucleotides of DNA, with no examina-
tion of intra-specific variation, and even omitting the orangutan from the analysis

MOLECULAR ANTHROPOLOGY 179

(Ruvolo et al. 1991). Significantly, this was also based on mitochondrial DNA, which
has a significant liability in the reconstruction of specific biological history. MtDNA
is contributed by the egg at fertilization, such that a child is a clone of mother and
unrelated to father, in contrast to the equal relationship of the child to both parents in
nuclear Mendelian genes. Imagine a medieval village invaded by Crusaders who
make — shall we say — unsolicited contributions to the gene pool. The offspring
would be half-Crusader, but that would not be detectable by a mtDNA analysis. There
would thus be a significant discordance between biological relationships discernible
by mitochondrial and by ordinary nuclear DNA. Indeed, subsequent analyses have
found this genetic region to be unreliable in preserving biological history faithfully
(Adkins & Honeycutt 1994; Honeycutt et a/. 1995).

Quite possibly, then, the scientists who authored the study of the 692 mtDNA
bases were using the word “resolution” in a new and heretofore unknown sense.

So (1) it is not at all clear that there are in fact two chronologically distinct
speciation events to be resolved here; and (2) if there are, it 1s not clear that we would
be able to tell with the molecular approach in common use now. In a different area
of molecular anthropology the sampled polymorphism really is the central focus,
namely the data on mitochondrial DNA as it might relate to human origins.

The New Molecular Anthropology: Mitochondrial Eve

The original Cann, Stoneking, & Wilson paper (1987) was a landmark of molecu-
lar anthropology, but for a more subtle reason than is generally appreciated. That
work was molecular in nature, but didn’t cast itself as being “versus morphology.”
Rather, it contrasted two hypotheses from the literature of morphology or paleoan-
thropology, subjected them to a test, and sided with one, the “Out of Africa” model.
In other words, the researchers self-consciously were using their “molecular” data to
try to distinguish between alternatives posed within the "morphology" literature. So
the battle lines here are not molecules versus morphology, but molecules plus
morphology versus morphology.

The problem with the study is that the authors carried out a fairly standard analysis.
That is, they threw their data into a computer, cranked it through a program called
PAUP, took the output, and ran with it. It is now clear that the output, the tree they
ran with, is sub-optimal ( Vigilant et a/. 1991; Maddison 1991; Templeton 1992, 1993;
Hedges ev al. 1992). Nevertheless the data and subsequent studies of genetic diversity
show a consistent pattern. For example, the study by Merriwether ef a/. (1991) broke
a human sample up into continental groups, and then asked the computer just to find
the breadth of diversity within each group (Figure 6a). They do not find Asia, Africa,
and Europe to contain roughly equal amounts of genetic diversity; rather, they find
the African sample to contain far more diverse variants than either the European or
the Asian. This in turn suggests that the genetic diversity being sampled has been
accumulating in Africa longer than elsewhere, as the geographically pooled data
imply (Figure 6b).

Cann et al. (1987) calculated that this diversity had been accumulating for about

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fa)
a
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io)
oy
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ab) =
nn, oO
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Africa Asia Europe

A mtDNA sequence
diversity

1 60) Sil eects

from all over the world
including Africa

exclusively from Africa

FIGURE 6. (A) General pattern of diversity in human mitochondrial DNA, broken down by
continent (based on Merriwether et al. 1991). (B) Pooled data.

200,000 years. Now, how does this relate to the origin of anatomically modem
humans? Unfortunately, not terribly clearly. Mitochondrial DNA can be treated as if
it were a single gene. You can trace the diversity in any gene across the human species
and find the date at which the diversity in that gene originated (Figure 7). Mitochon-
drial DNA sequences seem to be around 200,000 years old, which may well coincide
with the origin of anatomically modern humans. However, the diversity in histocom-
patibility genes, the ones that encode factors that determine whether skin grafts take,
predates the divergence of humans and chimpanzees, so is on the order of 10 million

MOLECULAR ANTHROPOLOGY 181

AGO oresent diversity

mtDNA HLA (3-globin

FIGURE 7. Different microevolutionary processes govern the spread of genetic variation.
Tracking the time of origin of contemporary human diversity yields different answers for
various DNA segments.

years. The breadth of beta-globin diversity is generally taken to be historically tied
to agriculture in the Old World — standing water, mosquitoes, malaria, sickle cell
anemia — and probably is on the order of thousands of years. So what we have is
genetic diversity for different genes, spreading by different microevolutionary proc-
esses, having originated at different times. I see the 200,000 year date as a coincidence
at best.

On the other hand, the late Allan Wilson, godfather of this research, initiated it
with characteristic insight. In 1981, he published a paper actually studying the
amounts of intra-specific genetic diversity encountered in the apes, relative to the

far more genetic diversity detectable in their mitochondrial DNA than humans. Now,
since the chimpanzee, gorilla, and human lineages were roughly as old as one another
(because they originated around the same time — the trichotomy), there had to be a
secondary reason for the human species appearing to be so relatively depauperate in
genetic diversity as sampled.

Presumably there was something in the demographic history of our species that
caused us to lose the genetic diversity retained by our closest relatives. What might
that be? The best way to lose genetic diversity is in founder-effect speciation (Figure
8). Ifa species originates as a small bud from an ancestral population, then you would
anticipate the new species to be considerably more genetically homogeneous than
the ancestor.

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sage of ee
res

Gorillas

Time

FIGURE 8. Humans, chimpanzees, and gorillas have been accumulating mtDNA diversity
for the same amount of time, so a secondary demographic process must be invoked to explain
why humans are so much less diverse.

So there are a lot of “ifs” here, but if there really is less genetic diversity in the
human species than in chimpanzees or gorillas, and if that is a result of the founder
effect operating on the demographic history of our group, and if Africans really are
more diverse than Europeans or Asians, then it is entirely possible that we may be
sampling the result of a founder effect in Africa marking the origin of our lineage,
anatomically modern Homo sapiens, a couple of hundred thousand years ago.

Obviously there are other alternatives, but it seems to me that their supporters are
preoccupied at the present time with explaining away these data.

The prospects for molecular anthropology lie in its ability to be self-critical. In the
phrase “molecular anthropology,” “molecular” is just an adjective. It only modifies
“anthropology”: it helps us tackle old problems with new kinds of data. But these
data, while transcending some of the difficulties of traditional datasets, have many
others of their own. Because of its mysterious nature, we’re obliged to be more critical
of molecular anthropology than of traditional anthropology. | think the history of the
endeavor bears this out well: without the context of the anthropological framework
into which they must fit, molecular data consistently prove to be almost valueless.

Ultimately, if molecular anthropology is not anthropology, what can it ever be?
The very phrase “molecular anthropology” itself, after all, was coined by a chemist
(Zuckerkandl 1963). I believe that molecular anthropology is a viable and indeed a
vital inter-disciplinary field, with a critical role in mediating the domains of genetics
on the one hand and anthropology on the other. Molecular anthropology thus can and
should serve to elevate genetics on anthropological issues and to elevate anthropology
on genetical issues.

MOLECULAR ANTHROPOLOGY 183

On one side, we have The Bell Curve (Herrnstein & Murray 1994), invoking
genetics para-scientifically to explain group differences in behavior — should not
molecular anthropology be crucial to this debate? On the other, we have the Human
Genome Diversity Project, proposed externally to anthropology (Cavalli-Sforza et
al. 1991), which has been represented to revolutionize or even to supplant anthropo-
logical knowledge and research (Anonymous 1995a). But without a sound anthropo-
logical framework — such as acknowledging the differences between constructed
cultural categories and natural biological categories, and the contact and histories of
indigenous peoples and their rights (Marks 1995b, 1995c; Anonymous 1995b) — the
HGDP has paradoxically begun to raise fundamental doubts about the role of genetics
vis-a-vis anthropology.

The issues that confront molecular anthropology today are vexingly similar to
those that have always faced those interested in applying genetic data to anthropo-
logical issues. In any inter-disciplinary endeavor there are reciprocal intellectual
responsibilities incurred, although disappointingly rarely met in molecular anthro-
pology. Our prospects involve continuing to make anthropology better in its integra-
tion of molecular research and, more importantly, to make molecular research better
as anthropology.

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Index

189

Index

ABO allele frequencies 170

adaptive radiation 10, 74,97, 103, 150

Africa 3, 6-7, 11, 14-15, 21, 23, 26-28, 32-33,
36-37, 76, 78, 81, 87-88, 93, 100-104, 107,
112, 115, 119-121, 125-126, 130-133, 135,
143-144, 147-150, 152-159, 161-163, 165,
170, 179, 182; See also Chesowanja; See
also East Africa; See Florisbad; See also
Irhoud; See also Kabwe; See Koobi Fora;
See also KRM (Klasies River Mouth); See
also Kromdraai; See also Makapansgat;
See also Nariokotome; See also Olduvai;
See also Olorgesailie; See alsoOmo; See
also Peninj; See also South Africa; See also
Sterkfontein; See also sub-Sahara; See also
Swartkrans; See also Taung; See also Tigh-
enif; See also Turkana

African origins (models of; recency of) 23-24,
26-28, 31, 35, 184

AHRM; See African origins (models of; recency
of)

Allen’s Rule 149

Alu insertion 22

anagenesis 22, 34,59

anterior dentition; See dentition

anthropophagy 16

AOAM; See African origins (models of; recency
of)

apes; Africa 5, 106, 135

apomorphy 16-20, 24, 62, 65-66, 70, 94, 116-
117, 121, 124-125, 127, 129-130

Arago (Spain) 16-17, 121, 125

archaic Homo sapiens 121, 126, 133, 136, 151,
159

Ardipithecus 3,80; ramidus 3, 80, 82, 89

Asia; See Dali (China); See Hathnora (India);
See India; See Indonesia; See Jinniushan
(China); See Maba (China); See Narmada
Valley (India); See Yunxian (China); See
Zhoukoudian (China)

Asian Neanderthals 127-128

Atapuerca (Spain) 9, 16-17, 118, 125-126, 131,
133, 139, 145, 152-153, 155; Gran Dolina
16; Sima 9, 16, 131, 152

Aurignacian assemblages 149-150, 152-153, 165

Australia 12, 118, 120, 147-149, 157, 160, 170

australopithecine; gracile 78, 99, 109; robust
71, 77-81, 84, 86-88, 99, 102, 104, 142: taxa
14, 110

Australopithecus 5-6, 9, 50, 78, 80-82, 87-89,
93-104, 106, 110-111, 113, 135-136, 138,
142-143, 157-160, 162; aethiopicus 78, 80-
87, 92-93,96; africanus 5, 78-84, 86-89, 92,

96-97, 99-100, 104-105, 110-111, 160: ana-
mensis 80,82; boisei 78, 80-84, 86, 88-89,
96,102; robustus 78, 80-84, 86,92,96; See
also Homo africanus, See also Paran-
thropus,; See also Paranthropus robustus

basicranial flexion 82, 84, 86, 146

biogeography 11, 76, 161

biotic subregions; lowland tropical forest 28;
Saharan 11, 28; Sahelian 28; — sa-
vanna/grasslands 28

bipedality 80, 97, 105-106, 110-111, 113, 137-
138, 141, 159-161, 163, 165

birth interval; See demographics

Black Skull (WT 15000) 78, 84

blood groups 2, 21, 169-171, 183, 185-186

bone chemistry; See isotopes and strontium

bottlenecks 26, 31, 38

brain size; See endocranial capacity

brain/body-size ratio 141

Broca’s area 142-143

Broom, Robert 5, 87, 93-96, 101

carnivores 138, 140-141, 146-147

caves 15, 132, 141, 144-145, 154, 160

cheek teeth; See dentition

Chesowanja (Africa) 94, 144

chimpanzee 5, 21, 36-37, 80, 82, 155, 172-174,
177, 180-182, 186; See also Pan

China; See Dali; See Jinniushan;
See Yunxian; See Zhoukoudian

chronocline 62-66, 69

chronometric dating 4

cladistic analysis 4-5, 12, 36-37, 51, 55-56, 62.
66, 69-71, 73, 75-76, 79-80, 105, 111, 117,
121,135, 155

cladistics 38, 55, 73-75

cladogenesis 10, 59, 118, 124

cold-adaptation 124

cosmetics; mineral pigments 146;
ornaments

cranial vault; See cranium, vault

craniometrics 12, 36

cranium 14-16, 18, 33, 81, 87, 94, 97, 99-100,
102, 106-107, 110, 112, 119, 131, 147, 155;

See Maba;

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