Page:Memoir upon the formation of a deaf variety of the human race (microform) (IA cihm 08831).pdf/8

 UPON THE FORMATION OF A DEAF VARIETY OF THE HUMAN RACE.

A PAPER PRESENTED TO THE NATIONAL ACADEMY OF SCIENCES AT NEW HAVEN, NOVEMBER 13, 1883.

Introductory Remarks.

The influence of selection in modifying our breeds of domestic animals is most 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.

But how can we ascertain the susceptibility of the human race to variation produced by selection? 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 contrary, sexual attraction often appears to operate after the manner of magnetical attraction — "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 unlikes attract.

Certain diseases are known to be liable to transmission by heredity. But we do not find epileptics 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 permanent variety of the race could be formed in this way, for the increased tendency to disease inherited by the offspring 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 pink-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.