GENETICS AND EUGENICS 



839 



Data on Human Heredity — Cont'd 



Mating-s Among Defectives 



It is obvious that persons who have inherited scaly skin, lobster 

 claws, amputated hands and feet, exostotic bones, or who might have 

 any of many other inheritable defects that incite pity or repulsion 

 will find difficulty in securing mates. When these abnormalities occur 

 as mutations, the afflicted persons are not likely to marry on their 

 own social level, but will probably mate with others who are of lower 

 grade mentally or who have other abnormalities that make them ob- 

 jectionable to normal people. Thus there is a tendency for defective- 

 ness to be precipitated to a social group that can clearly be called 

 dysgenic. By her process of eliminating the unfit who could not sur- 

 vive the fierce struggle for existence. Nature formerly kept this group 

 at minimum size. Today its numbers are being added to, not only by 

 recruits from higher groups who have a poor heredity either by un- 

 fortunate segregation of undesirable genes or by the occurrence of 

 such mutations as have been mentioned, but also by increased repro- 

 duction by the members of the dysgenic group itself. 



The Differential Birth Rate 



Nature keeps her creatures fit by giving reproductive advantage to 

 the best members of each species. Various dioecious animal forms 

 produce from dozens to millions of young per pair from which, on an 

 average, two individuals are selected to replace the parents. As a rule, 

 the two selected are the ones that are strongest and the most free of 

 defects — these are usually the ones that are best adapted to their en- 

 vironment. Man has, in the case of his own kind, preserved the weak 

 and defective individuals that Nature would have eliminated. This has 



