674 



THE PLEISTOCENE PERIOD 



inherent evidence of considerable antiquity. The European cave 

 evidence seems to have no strict counterpart in America. 



The association of man with extinct animals is a phenomenon 

 that may mean the extension of man's presence backward, or the 

 extension of the animals' presence forward; and to this double- 

 faced problem research has not yet furnished a final key. Obviously, 



Fig. 547. A gravel bluff formed by the undercutting of the adjacent river. 

 (After Holmes.) 



Fig. 548. The same at an early stage of talus formation. 



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Fig. 549. The same at a late stage, when the slope has become nearly stable. 



however, the larger the number of animal types not known to have 

 lived this side the last glacial stage whose remains are commingled 

 with human relics, the stronger the presumption of man's presence 

 before the close of the glacial period. From this point of view, 

 the European case seems to be strong. 



There is one further feature in the European case that is, at 

 least, suggestive. Two climatic groups of animals are associated 



