What then is the relation of the palæolithic hunter of reindeer in France and Britain to the glacial period? Is he pre- or postglacial? The only evidence on the point is that offered by the associated mammalia which occupied France, Germany, and Britain before and after the point of minimum temperature was reached in these latitudes. Man may have inhabited the caves not merely of France, but of Devonshire and Somerset, at any time during that long period. The position of the palæolithic refuse-heap discovered by Prof. Fraas at Schussenreid, resting on a moraine of the extinct glacier of the Rhine, proves that the palæolithic Eskimos lived in Suabia after the retreat of the glacier when the temperature became warmer, towards the close of the pleistocene age or in the later glacial stage. The same conclusion has been arrived at by Mr. Prestwich as to the sojourn of palæolithic man (of the river-bed type) in Bedfordshire and Suffolk, the gravels in which the implements are found being of a later age than the boulder-clay of those districts. We have therefore proof that man lived in Germany and Britain after the maximum glacial cold had passed away, and we may also infer with a high degree of probability that he migrated into Europe along with the pleistocene mammalia in the preglacial age.
Test of age of contents of caves in Glaciated Districts.
The probable date of the introduction of the contents into ossiferous caves in glaciated areas may be ascertained by an examination of the river deposits. If the animals found in the caves inhabited the surrounding country after the melting of the ice, their remains will occur in the postglacial gravels. If they are not found, it may be inferred that they had retreated from the district, before the latter were deposited. It is obvious that they could not have lived in any district while it was covered with ice or by the sea. It may therefore be concluded that their remains in the caves were most probably introduced before the glacial conditions had set in. Preglacial deposits in a cavern would be protected from the grinding of the ice-sheet, the action of the waves in the depression, and re-elevation of the land, and the subsequent glacial erosion which would inevitably destroy nearly all the fluviatile ossiferous strata. By this test the pleistocene strata in the Victoria Cave, near Settle, may be considered preglacial, as well as the hyæna-den at Kirkdale, which has always been referred by Prof. Phillips to that age. If this be allowed, the small fragment of human bone found by the Settle Cave Exploration Committee in the former cave in 1872 establishes the fact that man lived in Yorkshire before the glacial period. The man to whom it belonged was probably devoured by the hyænas which dragged into their den the woolly rhinoceros, reindeer, and other creatures whose gnawed bones were strewn on the floors.
CHAPTER XII.
CONCLUSION.
Classification of Pleistocene Strata by means of the Mammalia.—The late, middle, and early Pleistocene Divisions.—The Pleiocene Mammalia.—Summary of characteristic Pleiocene and Pleistocene Species.—Antiquity of Man in Europe.—Man lived in India in Pleistocene Age.—Are the Palæolithic Aborigines of India related to those of Europe?—Palæolithic Man lived in Palestine.—Conclusion.
The animals inhabiting the caves have been enumerated in the last three chapters, and we have discussed the inferences drawn from their distribution as to the pleistocene climate and geography of Europe. It remains for us now, in conclusion, to define the pleistocene, and to see in what relation it stands to the pleiocene period.
Classification of Pleistocene Strata by means of the Mammalia.
The pleistocene period was one of very long duration, and embraced changes of great magnitude in the geography of Europe, as we have seen in the [ninth] and [tenth] chapters. The climate, which in the preceding pleiocene age had been temperate in northern and middle Europe, at the beginning of the pleistocene gradually passed into the extreme arctic severity of the glacial period. This change caused a corresponding change of the forms of animal life; the pleiocene species, whose constitutions were adjusted to temperate or hot climates, yielding place to those which were better adapted to the new conditions. And since there is reason for the belief that it was not continuous in one direction, but that there were pauses or even reversions towards the old temperate state, it follows that the two groups of animals would at times overlap, and their remains be intermingled with each other. The frontiers also of each of the geographical provinces must naturally have varied with the season; and the competition for the same feeding-grounds between the invading and retreating forms must have been long, fluctuating, and severe. The passage, therefore, from the pleiocene to the pleistocene fauna might be expected to have been extremely gradual in each area. The lines of definition between the two are to a great extent arbitrary, instead of being marked with sufficient strength to constitute a barrier between the tertiary and post-tertiary groups of life of Lyell, or between the tertiary and quaternary of French geologists. The principle of classification which I have proposed[267] is that offered by the gradual lowering of the temperature, which has left its mark in the advent of animals before unknown in Europe; and according to it I have divided the pleistocene deposits into three groups.