1 68 ORGANIC EVOLUTION 



of the factors of evolution, he is still subject to them and 

 is still being modified by them to-day. Disease and unfavor- 

 able climate kill those who are unable to resist them, while 

 the stronger survive. Men fail in the struggle for existence 

 and become submerged and disappear. Natural selection 

 is constantly removing those who are unable to resist the 

 pressure of the adverse conditions of life. This is the same 

 process we have seen among the lower animals and the 

 plants, and has the effect of making man more fit for his 

 surroundings by eliminating the less adapted. 



Sexual selection also is operative, more so among man- 

 kind than in any other group of animals. There is closer 

 scrutiny and more careful choice is exercised in human 

 marriage than in the mating of any of the lower animals. 

 There is an important difference to notice. Among human- 

 kind, at least among more highly civilized men, choice in 

 marriage is based more largely upon intellectual and moral 

 attractions and less upon physical attractions than is the case 

 among lower animals. Among lower forms sexual selection 

 secures chiefly ornamentation or fine voice. Among men it 

 is more those of good intellect, of pleasing disposition, of 

 right character, who are chosen; sexual selection thus serving 

 to increase and perpetuate these characteristics. 



Segregation also is an important factor in human evolu- 

 tion. The fact that the Chinese live in Asia and the negroes 

 in Africa, has prevented intercrossing between these two 

 races, which, if it had taken place, would have changed the 

 character of both races. In any community there are many 

 important segregating factors. There is in America a well- 

 nigh universal distaste toward marriage between negroes and 

 Caucasians, and this has had an important effect upon the 



