The origin of man from an ape-like ancestor[9] is generally admitted, but owing to the incompleteness of the palæontological record we are still in ignorance as to the circumstances, while the place is generally put vaguely as somewhere in Asia, and the time as the late Tertiary (Prof. Elliot Smith places it near the Siwalik hills in the Miocene). For this early period we are reduced to speculation, in which we may reasonably utilize the facts which we have gained about climatic variation.
The chief problem to be explained is why man’s arboreal ancestor left the safe shelter and easy food supply of his primæval forest and ventured forth into the plains. An article by Professor J. Barrell,[10] of Yale University, gives a plausible account of the change, putting it down to necessity, and not to choice. His theory is that the human ancestor lived in the forests spread over Asia, then a vast well-watered plain, during the middle-Tertiary period. Then the gradual uplifting of the Himalayas and other mountain ranges caused a decrease in the rainfall of central Asia, so that ultimately the forests were unable to thrive, and gradually gave place to steppe conditions. The change was slow enough to give the less specialized inhabitants of the forest time to change their habits and evolve into forms suitable to a terrestrial life, and the chief of the animals which took advantage of this period of grace was the pre-human. Forced to live on the ground, with a diminishing food supply, only the most progressive individuals were able to survive, and evolution was rapid. The changing type was saved from being submerged in the great mass of the original type in the forests which continued to exist further south by the impassable wall of mountains. Major Cherry[11] considers that there is sufficient evidence to prove that a portion of this evolution took place on the seashore, an environment which would have been much more favourable to a small ape-like animal than the open steppe would have been. It is quite likely that the earliest migrations, such as that which carried Pithecanthropus to Java, took place along the shore. But after a time, when increasing brainpower and the use of primitive stone implements enabled man to take the offensive against the larger animals, the centre of activity changed to the steppes. A familiar view of the early development of man was advocated by W. D. Mathew,[12] who writes: “In view of the data obtainable from historical record, from tradition, from the present geographical distribution of higher and lower races of men, from the physical and physiological adaptation of all and especially of the higher races, it seems fair to conclude that the centre of dispersal of mankind in prehistoric times was central Asia, north of the great Himalayan ranges, and that when by progressive aridity that region became desert it was transferred to the regions bordering it to the east, south and west. We may further assume that the environment in which man primarily evolved was not a moist tropical climate, but a temperate and more or less arid one, progressively cold and dry during the course of his evolution. In this region and under these conditions, the race first attained a dominance which enabled it to spread out in successive waves of migration to the most remote parts of the earth.”
We do not know anything of the migrations of the Eolithic and earlier Palæolithic races, except that they spread rapidly over a considerable portion of the earth. Both migration and evolution, especially mental evolution, must have been accelerated by the great changes of climate which were taking place. In the Mindel-Riss interglacial period we know of two types, the Piltdown man (Eoanthropus dawsoni) and the Heidelberg man (Homo heidelbergensis), the latter a true man, though probably not on the direct line of evolution of Homo sapiens. The stress of the succeeding second Glacial period was too great for Eoanthropus, which appears to have died out, but Homo, probably an Asiatic or African type similar to H. Heidelbergensis, survived. The next form, associated with Mousterian implements, is Neanderthal man (H. neanderthalensis), who closely resembled modern man, and all the remains of races which lived subsequently to the last glaciation are those of modern man (H. sapiens), including the magnificent Cro-Magnards and the negroid Grimaldi race. Thus each glaciation has been marked by a step upwards in the scale of humanity; does this mean that the coming of the super-man is contingent on another glacial epoch?
BIBLIOGRAPHY
Barrell, J. “Probable relations of climatic change to the origin of the Tertiary Ape-man.” Scientific Monthly, New York, 4, 1917, p. 16.
Mathew, W. D. “Climate and evolution.” Annals New York Acad. Sci., 24, 1915, p. 212.
London, British Museum. “A guide to the fossil remains of man....” London, 1918.
CHAPTER XIX
CLIMATE AND HISTORY
It is a remarkable fact in human history that civilization began in regions which are at present inhabited chiefly by backward races, and the centres of progress have shifted from one country to another with the passage of time. Many accidental factors—position on trade-routes, possession of special mineral advantages, and so on, have undoubtedly played a part in this, but it will not be difficult to show that climatic fluctuations have also had their share.