CRITERIA REQUISITE TO A GLACIAL AGE 65 



a more important matter to us, it is the more important that its 

 evidence be sound. The notion that the life-history of one 

 grand division is to be "brought into accord" with that of 

 another is a perilous guide. In certain general aspects, the life- 

 history of the several subdivisions may indeed have points of 

 accord, but in its special phases divergence is quite as much the 

 rule as concordance. In any given case, the probabilities are 

 that a given form originated in one grand division rather than 

 in all, and that more or less time elapsed before it migrated to 

 distant regions. There is therefore no presumption that all the 

 early stages of evolution will be found on all the continents. 



Nor do I see any good scientific reason to desire one result 

 rather than another. I see no scientific grounds for a predis- 

 position to match European antiquity by American antiquity, 

 or the European stages of evolution by American stages of 

 evolution. It is quite as much in the interest of ethnological 

 science, so far as I can see, to limit the duration of the human 

 species on the western continent as it is to extend it. Given three 

 or four great divisions of the earth's surface in which a species 

 may develop in measurable independence, probably as much, 

 and perhaps more, can be learned from the introduction of the 

 species into these several divisions at different and rather widely 

 separated intervals, as can be learned by its introduction into all 

 of them simultaneously, or in close succession. Evolution 

 through periods of different lengths in the different divisions 

 would probably show at least as much, if not more, of the rate 

 and nature of development as would evolution for equal periods 

 in all the divisions. We shall probably learn quite as much of 

 the great lessons of human evolution if it shall be shown that 

 the American races have developed since the glacial period, so 

 far as they are endogenous, as if it shall be shown that the period 

 reaches back to one or another of the interglacial epochs or to 

 the preglacial period. In any case, to the ideal scientist, it is 

 purely a question of fact to be settled by demonstrative evidence. 

 Our concern here is what constitutes demonstrative evidence. 



Evidefice to be sought in the glacial formations themselves. — 

 Grounds for assigning man to a glacial period are to be sought 



