Page:Early Man in Britain and His Place in the Tertiary Period.djvu/151

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The Pleistocene mammalia might reasonably be expected, from the manner in which the Asiatic migration took place, to have been in Europe before, during, and after the Glacial period. As the ice advanced southwards it pushed the arctic mammalia southwards, and caused them to encroach on the temperate and southern mammalia. When it retreated northwards the animal life swung northwards. These considerations, necessary from the facts brought forward in the preceding pages, will be found in the next chapter to be proved by a critical examination of the river deposits and the contents of caverns.

From the large percentage of living species which we have noted in the preceding chapter, we might have inferred that the time was at hand for the arrival of man. The greater part of the living European mammalia were present, and the world was then in the stage of evolution in which man might be expected to play his part. In the next two chapters we shall see at what stage of the Pleistocene age he appears, and we shall examine the evidence from which it may be concluded that there were two races—the River-drift men and the Cave-men—in Europe during the long series of ages represented by the Pleistocene period.