706 THE ICE AGE IN NORTH AMERICA. 



Conclusion. In the discoveries narrated above of man's 

 relation to the glacial epoch the study of every class of glacial 

 phenomena becomes invested with all the higher interest of 

 historical research. Signal changes were introduced into the 

 world's history by the conditions which accompanied the 

 Glacial epoch. In America as well as in Europe this advent 

 of northern cold greatly disturbed the conditions of animal 

 life, and, we may well suppose, directly led to the extinc- 

 tion of many animal species. In North America the camel, 

 the hippopotamus, the rhinoceros, the tapir, the mammoth, 

 the horse, the mastodon, were abundant at the opening of 

 the Quaternary age. Their complete extermination is one 

 of the most startling facts in geology. But, as Darwin has 

 so well shown, the effects of a glacial advance are by no 

 means limited to the region directly reached by the ice. In 

 pushing southward the plants and animals of the northern 

 part of the continent, the struggle for life in the more 

 crowded quarters of the decreasing congenial portions of the 

 country became more and more intense, and thus doubtless 

 was brought about much of the extinction of species which 

 the geologists have to record as having taken place in the 

 early part of the Quaternary period. The evidences of 

 man's existence in North America before the close of the 

 Glacial period would indicate that he too shared in the sharp 

 struggle which ensued with the new and rapidly changing 

 conditions of that time. Did he also, like so many of his 

 companions among the larger animals, share in this extinc- 

 tion ? The sharpness of the transition from the palaeolithic 

 to the neolithic type of implements, as we pass out from the 

 Trenton gravel into the shallow soil above it, would seem to 

 indicate an absolute distinction between the two succeeding 

 races. But even so, whether the first became extinct from 

 natural causes, and the other simply came in later as colonist, 

 or whether the latter as conqueror exterminated the first, 

 may always remain a doubtful question. It is possible that 

 the Eskimo is the lineal descendant of preglacial man in 

 America, and the conditions of life with which the Eskimo 



