120 MAN, THE ANIMAL 



human characters that are in part inheritable. 

 This has led thinkers along this line to advocate 

 certain restrictions for the physically unfit which 

 raises such a question as the following: Is it right 

 for an imbecile to beget children when we know 

 that imbecility is inherited as a unit character and 

 is usually dominant even if but one parent suffers 

 from this malady? In some states laws have been 

 passed prohibiting the marriage of mental de- 

 fectives. 



If all of these traits are inherited, then the 

 characteristics upon which character is built are 

 heritable. This leaves to man the problem of 

 training, developing and unfolding but not of 

 creating characteristics. Man possesses a com- 

 paratively simple digestive system which we have 

 found to exhibit a low degree of efficiency. On 

 the other hand, he has a remarkably specialized 

 nervous system which enables him not only to 

 control his own physical destiny but also his 

 environment. Both of these organs are heritable 

 qualities in man and always will be. The in- 

 heritance of normal man is limited in that he is 

 never very tall or very short — other charac- 

 teristics are similarly restricted. There is no 

 record of marked change in historic time in the 

 physical and mental traits of mankind. There 

 will always continue to be chance combinations of 

 genes as the chromosomes fuse in fertilization that 



