148 EVOLUTION OF THE EARTH 



nian in the age of Pericles was as much superior to the average 

 Englishman of today as the Englishman is superior to the 

 African. Although a few students still claim that all races 

 possess equal possibilities if given equal opportunities, their 

 conclusions lack statistical foundation. Judged by their 

 achievements and by all the exact tests yet available, races 

 differ as do individuals, although not to so great an extent. 



What causes these racial differences? We cannot answer 

 until the biologists give us more light on the origin of the new 

 forms called mutants. If it be asked, however, what pre- 

 serves the mutants and thus gives rise to new racial qualities, 

 we can answer with considerable certainty. Environment by 

 means of natural selection allows some types to perpetuate 

 themselves indefinitely, while it rigidly exterminates others. 

 Among the various environmental factors, climate is appar- 

 ently the most important. As Professor Lull has said in a 

 previous lecture: "Changing environmental conditions stimu- 

 late the sluggish evolutionary stream to quickened movement. 

 Whenever it has been possible to connect cause and effect, 

 the immediate influence is found to be generally one of 

 climate." 



Inherent mental capacity. The American Indians seem to 

 furnish one of the best examples of the influence of climate 

 upon mental capacities. 1 Practically all authorities agree that 

 the Indian is endowed with a relatively conservative type of 

 mind. He has great powers of observation, of patience, of 

 endurance, and also of action when some crisis suddenly stirs 

 him. He is lacking, however, in originality, in the power of 

 adaptation, and in the quick insight and inventiveness which 

 make the Japanese so competent in seizing what they want in 

 European civilization. It seems probable that the Indians 

 owe much of their mental status to the fact that they appar- 



1 For a fuller discussion of this matter see "The Red Man's Continent," Yale 

 University Press, 1918. 



