404 HEREDITY AND ENVIRONMENT 



into such relations to natural laws that he can 

 profit by them. 



1. Selective Breeding the only Method of 

 Improving the Race. — It is surely not possible 

 to improve on nature's method of eliminating 

 the worst lines from reproduction. This has 

 been the chief factor in the establishment of 

 races of domesticated animals and cultivated 

 plants, though as we have seen it has probably 

 had nothing to do with the origin of mutations. 

 The history of such races shows that evolution 

 may be guided to human advantage by intelli- 

 gent elimination and selection, and probably 

 any hereditary improvement of the human race 

 must be accomplished by this means, though of 

 course such elimination and selection can ap- 

 ply only to the function of reproduction. The 

 method of evolution by the elimination of per- 

 sons, the destruction of the weak and cowardly 

 and antisocial, which was the method practiced 

 in ancient Sparta, is repugnant to the moral 

 sense of enlightened men and cannot be al- 

 lowed to act as in the past; but the worst 

 types of mankind may be prevented from pro- 

 pagating, and the best types may be encour- 



