EVOLUTION OF MAN 169 



development of the two races. Intermarriage between those 

 of different social strata is unusual, culture and wealth thus 

 effecting segregation. Religious belief has had an important 

 effect in causing segregation in marriage. It would be im- 

 possible to enumerate all the efficient causes of segregation 

 among humankind. 



Let us look a little further at man's relation to natural 

 selection and sexual selection. First as to natural selec- 

 tion : While man, like all other animals, is subject to natural 

 selection, he is less so than any other species, so far as physi- 

 cal factors are concerned. Our great intellectual develop- 

 ment enables us to escape from many phases of the struggle 

 for existence. We build houses which protect us from the 

 inclemency of the weather. We have fires to protect us 

 from the cold of winter. We cook our food, thus largely 

 escaping the internal parasites which so commonly infest the 

 lower animals. W r e have physicians who enable us to sur- 

 vive diseases which otherwise would destroy us. By cultiva- 

 tion of the soil and by raising flocks and herds we increase 

 the productiveness of the earth, making it support a far 

 greater population than would otherwise be possible. When 

 crops fail in certain localities, whole nations are saved from 

 extermination by the great development of our means of 

 transportation, which bring food from distant regions to save 

 the starving. In thousands of ways we are relieved by our 

 greater intelligence from much of the stress of the struggle 

 for existence. Natural selection plays a less prominent part 

 among men than among plants and the lower animals. 



Of course this partial elimination of natural selection is a 

 very great advantage, producing inestimable good to man, 



