GENETICS IN THE SERVICE OF MAN — GLASS 311 



Negro population, it will take approximately 2,000 years before assim- 

 ilation becomes complete. Of course, the process will undoubtedly 

 accelerate as the two populations become less distinguishable, and the 

 gene flow from the Negro into the white population, till now negligible 

 in amount, will some day become appreciable. Meanwhile, it is im- 

 portant to realize what a disastrous increase in the proportion of 

 hereditarily afflicted persons would result if our present populations 

 were for any reason — say, as the aftermath of another world war — 

 to be broken up again into small units. 



By surrounding himself with a social environment, mankind has 

 unwittingly modified the rigor of natural selection in many ways. 

 The price we must pay, in the end, for the mercies of medical care and 

 surgical aid is the dysgenic increase in the frequencies of certain detri- 

 mental genes whose effects we have learned to ameliorate. Thousands 

 upon thousands of diabetics who in a former day would have died 

 early in life are now saved by insulin to live relatively normal lives, 

 and, of course, to pass on the gene responsible for their diabetes to 

 their descendants. Myopia is no longer a grave handicap in life; 

 hearing aids alleviate certain types of deafness. Probably no one 

 would have it otherwise. Yet to contemplate a future population 

 composed largely of persons who must wear both glasses and hearing 

 aids, and must start the day by inserting their false teeth and taking 

 first an insulin injection in one arm and then allergy shots in the other, 

 is none too pleasant. To say the least, medical science is steadily 

 increasing the load it must carry. 



Another instance of the unconscious direction of human evolution 

 lies in the differential reproduction of economic and cultural groups. 

 The differential reproduction of the several races may be passed over, 

 since there is no valid evidence that any known hereditary differences 

 between races alter viability or fertility, or affect any eugenic desidera- 

 tum, such as intelligence. But there is little doubt that there is some 

 positive correlation between intelligence and economic and cultural 

 level, in such countries as the United States and Great Britain. In 

 these countries the reproductive rate varies inversely with income. 

 Theoretically, this should result in a decrease of those genes contribut- 

 ing to high intelligence, although the decrease may be slow. Yet the 

 only extensive study on the subject, that of the I. Q.'s of virtually all 

 Scottish school children over a 15-year period, 1932 and again in 1947, 

 has revealed no decline whatsoever. 



The various measures of positive and negative eugenics may now be 

 considered. The former comprises four methods, all in use in certain 

 States or countries. 



The method most widely used is that of segregating males and fe- 

 males in separate institutions, such as prisons, mental hospitals, or 



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