MAN IN THE MODERN WORLD

from his simian ancestors that ideas as to the influence of climate on
this phase of his history are highly speculative. It can scarcely be
doubted, however, that the progressive desiccation of the world that
took place in the late Cenozoic Epoch helped to drive our ancestors
down from the trees and out into the plains. We know that the
Himalayas were elevated at this time; and it has been plausibly
suggested that man originated to the north of them. For, as the land
here grew drier, the forests shrank southward, where they were met
by the impassable mountain barrier, and disappeared from Central
Asia. Their anthropoid inhabitants were therefore forced either to
disappear too or to become adapated to the new conditions, growing
more terrestrial and more carnivorous. However this may be, men of
a sort were undoubtedly in existence befpre the beginning of the Ice
Age, over half a million years ago. But until we shall have found
more traces of Eolithic and Lower Paleolithic man in other parts of
the world than Europe (which was doubtless a mere outlier of human
development) we shall not be able to piece together the fascinating
story of the influence of the different advances and retreats of the ice,
or the slow progress of Old Stone Age man. Pekin man and recent
discoveries in Africa show how complex the picture was.

When the ice of the glacial period was still in the early stages of its
last retreat, the storm belt must have lain over North Africa, making
what is now the Sahara green and fertile. It was through Africa, and
perhaps eventually from southern Asia, that Europe received its
modern men, perhaps about 20,000 B.C. (Until about 4000 B.C. our
dating must be regarded as provisional only; for the most part the
chronology of Peake and Fleure, in their series, The Corridors of Time,
is here followed.)

Gradually, as the ice withdrew northward, the belts of climate
followed it up. The Sahara began to come within the limits of the
dry belt. To-day, in certain parts of the Sahara, crocodiles and
certain fresh-water fish exist in scattered oases. But these oases are
isolated, without possible connections with other bodies of water.
The water beasts that inhabit them are living in the sparse remnants
of the well-watered, and indeed probably swampy, expanse of ver-
dure that once spread over the Great Desert. This drying of the
Sahara must have sent wave after wave of migrating men out of it, both
northward and southward.

Meanwhile the zone of greatest fertility and greatest human vigour
came to lie along the Mediterranean, through Mesopotamia and
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