UPON THE FORMATION OF A DEAF VARIETY OF THK IIIMAN RACE. 



A PAPElt I'BEtiENTEI) TO THE NATIONAL ACADEMY OF SCIENCES AT NEW HAVEN, NOVEMBER 13, 1883. 



Introductory Remarks. 



The influence of selection in niodifjing our bieetls of domestic animals is inost marked, and it 

 is reasonable to suppose that if we could apply selection to the human race we could also produce 

 modifications or varieties of men. 



Uut how can we ascertain the susceptibility of the human race to variation produced by selec- 

 tion? We cannot dictate to men and women whom they shall marry, and natural selection no 

 longer influences mankind to any great extent. 



We can see around us everywhere evidences of the transmission by heredity of characteristics, 

 both desirable and undesirable, but at first sight no general selective influence appears to be at 

 work to bring about the union in marriage of persons possessing the same congenital peculiarities- 

 On the contrarj', sexual attraction often appears to operate after the manner of maguetical attrac- 

 tion — " unlike poles attract, like poles repel." Strong, vigorous, and robust men naturally feel 

 a tenderness for weak, delicate, and fragile women, and are generally repelled by physical strength 

 and masculine traits in one of the opposite sex. Even in such characteristics as the color of the 

 hair and eyes, it often appears that uulikes attract. 



Certain diseases are known to be liable to transmission by heredity. But we do not find epi- 

 leptics marrying epileptics, or consumptives knowingly marrying consumptives. Even though 

 persons afflicted with the same hereditary disease were to intermarry for a number of successive 

 generations, it is doubtful whether any i^ermanent variety oi" the race could be formed in this way, 

 for the increased tendency to disease inherited by the oftspring would probably cause a greater 

 tendency to premature death and ultimately occasion the extinction of the variety. 



On the other hand, it is reasonable to suppose that the continuous intermarriage of persons 

 possessing congenital defects not associated with diminished vitality or vigor of constitution would 

 result after a number of generations in the production of a vigorous but defective variety of the 

 race. For instance, the absence of coloring matter from the skin and hair is a defect occasionally 

 found among human beings, and we may learn from the success of attempts to propagate Albinism 

 among animals, that we would probably produce a [)ink-eyed, white-haired variety of the human 

 race by causing Albinos to marry one another ; but this is only speculation. We cannot control 

 the marriages of men as we can the breeding of animals, and at first sight there seems to be no 

 way of ascertaining how far human beings are susceptible of variation by selection. 



179 



