240 SOCIAL HEREDITY AND SOCIAL EVOLUTION 



race that fails to preserve a goodly number of chil- 

 dren to adult life is doomed to extermination, no 

 matter how rapidly it reproduces. Families are 

 ever disappearing through lack of reared offspring. 

 Even races are vanishing from the same cause. This 

 principle affects races all over the world. There is 

 a constant elimination of human families and races. 

 The savage races are everywhere being extermi- 

 nated, the barbaric races are disappearing under 

 conditions that we can hardly understand. Even 

 the Negro race in the United States, at least in the 

 larger cities, in spite of the rapidity of multiplica- 

 tion, appears, according to recent statistics, to be 

 undergoing a decrease in numbers, which, appar- 

 ently, indicates an extermination. 



Selection Among the Lower Classes. — These processes 

 are slow, and we can hardly understand what factors 

 contribute to the success or failure of a family or 

 race to perpetuate itself in modern civilization. A 

 few factors, however, may be referred to as most 

 important, and in their consideration it must be 

 borne in mind that we are discussing the ability to 

 rear offspring, not simply to produce them. The 

 checks to this power of leaving productive offspring 

 act quite differently in the different strata of society. 

 People at the bottom of the scale generally produce 

 more children than the higher classes; but even here 

 the reproductive efficiency, especially the power of 

 rearing children, is reduced by many causes. First, 

 we have excessive work, for it is a well-known fact 

 that excessive physical labor is destructive of the 

 ability to leave numerous offspring. Second, the 

 evils of sensuality remove a large number from the 

 reproductive class. But more important than such 



