252 



ESSENTIALS OF ZOOLOGY 



Matings 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 

 Avill 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 



Fig. 83. — Family from Brazil showing hereditary absence of hands and feet. 

 The man at the right rear is the uncle of the children shown. The father, who is 

 dead, had the same deformity. Of the twelve children born, six were normal and 

 six were deformed. (From Holmes, Human Genetics and Its Social Import, 

 McGraw-Hill Book Company, Inc.) 



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 



