302 ANKTUAL REPORT SMITHSONIAN INSTITUTION, 1941 



As scientific knowledge improves, we learn more and more about 

 inherited susceptibility, or predisposition, toward certain diseases, 

 as well as resistances or even immunities. We learn that some types 

 of illness formerly supposed to be hereditary are only partially or 

 not at all in this category, while in other cases inherited character- 

 istics are found to predispose an individual toward a given disease. 

 Among those in which inheritance is a definite factor are rheumatic 

 fevers in childhood, a few rare types of cancer, color-blindness, a 

 number of disorders of the eye, baldness, and albinism. Certain 

 sorts of feeble-mindedness are hereditary. The geneticists are in- 

 creasingly reluctant to draw a hard and fast line between environ- 

 mental and hereditary factors; yet in regard to 10 of the 12 most 

 serious diseases, environment on the whole seems more important 

 than heredity. 



These recent scientific revelations have enormously altered our 

 conception of eugenics. We understand now for tlie first time how 

 mutations occur, through destruction or alteration of the genes. 

 From the individual's point of view, there are good and bad genes, 

 but the good ones enormously outnumber the bad. Since nearly all 

 changes in the genes are destructive, and consist in taking something 

 away, under the law of averages most mutations are undesirable. 

 They produce an organism limited in some respects, in comparison 

 with its parent, and therefore probably somewhat less fitted to cope 

 with its environment. 



In a state of nature, this does not matter greatly, for it is offset 

 by natural selection — the survival of the fittest. Mutations that are 

 disadvantageous tend to die out ; good ones help the organism to sur- 

 vive and to transmit its desirable "symphony of genes" to the next 

 generation. But unfortunately civilization as it has existed for the 

 past few centuries tends to reverse this process. We are moving in 

 the direction of keeping everyone alive, the unfit as well as the fit, 

 and permitting nearly all of them to transmit their genes to their 

 children. Many of the leading geneticists of the world believe that 

 this process, continued long enough, would so reinforce the morbid 

 genes as to bring about the degeneration of the race. 



To say this is not, however, to accept the theories of those who are 

 demanding wholesale compulsory sterilization of the unfit. The 

 geneticists realize better than the amateur enthusiasts what an 

 enormously difiicult and complicated subject this is. They advocate 

 sterilization in certain definite cases of proved hereditary feeble- 

 mindedness and insanity, partly to put an end to bad genes and partly 

 because people of low or unstable intelligence bring up their children 

 badly. In other cases of undesirable heredity, the experts recom- 

 mend voluntary abstention from parenthood. 



