GENETIC EFFECTS 23 



Nevertheless the increase in gene frequency, in defects that are undesirable merely from a 

 personal standpoint, due to mutations of class B, must certainly be given weight in appraising 

 the effects of increase in ionizing radiations. There is already much evidence on rare family 

 traits that probably belongs here. 



As far as burden to society is concerned, class 6, antisocial behavior, probably comes 

 first. A priori one might suppose that selection would have been redirected especially into the 

 channel of social adaptability since the advent of civilization made certain types of behavior, 

 that had been highly adaptive in primitive life, highly disadvantageous to society. This, how- 

 ever, is on the assumption that heredity is involved to a sufficient extent to give a handle to 

 such temperamental traits as egotism, aggressiveness, impulsiveness, and their opposites, but 

 disentanglement from the effect of social training makes appraisal extraordinarily difficult. 

 The effect of increased radiation in increasing character defects that lead to antisocial behavior 

 is not likely to be determined soon. 



Category 7, socially burdensome subnormal physical constitution, brings us to the heart 

 of the problem of appraisal. It is possible, on the one hand, that most defects of this sort are 

 due to heterozygous effects of mutations of class B with the consequence that most of the social 

 burden must be included in a genetic burden that is expected to rise with increased radiation. 

 On the other hand, most of it may be either accidental or due to mutation of class A and thus 

 not subject to appreciable increase with increased radiation. In the last case, the current bur- 

 den is the price that society must pay for the diversity in categories 1 to 4 that is essential for 

 modern civilization. The problems for investigation are thus those of the heritability of devi- 

 ations in this category and the proportion of the heritable portion that is due to mutations of 

 type B, especially Bl. 



The situation is the same with respect to category 8, the burden from subnormal intel- 

 ligence. A considerable portion is certainly non-genetic (effects of birth injury, early infec- 

 tion, etc.). Another portion is probably the price that must be paid for a distribution of intel- 

 ligence with a peak best adapted for performance, without too much boredom, of the great 

 bulk of the work needed in the present imperfect state of society, but an upper tail of suffi- 

 ciently high intelligence to furnish necessary leadership. Under multifactorial heredity this 

 implies a somewhat corresponding tail of low intelligence. Some of the burden is undoubtedly 

 due to mutations of class B. Again we have the problem of heritability and apportionment of 

 the heritable portions to classes A and B for investigation. 



The case of category 9 ( burden from physical breakdown, after maturity but before the 

 debt to society has been paid) is also similar. Here accidental causes probably play a greater 

 role than in feeblemindedness but it is reasonably certain that genetic factors are of consider- 

 able importance in such matters as susceptibility to tuberculosis and other infectious diseases, 

 diabetes, circulatory diseases, and cancer. The problems are the same as before. 



In the case of mental breakdown (category 10), heredity undoubtedly plays a very im- 

 portant role. Huntington's chorea is due to a dominant gene with 100% penetrance for all 

 who live long enough. It is definitely due to a mutation of class Bl and does very consider- 

 able social (and personal) damage. 



The most important part of the burden in this category is, however, that due to the major 

 psychoses, schizophrenia, and manic depressive reaction. Penrose, in the report of the British 

 Medical Research Council, adopts Kallmann's interpretation of a recessive predisposition to 

 schizophrenia. He assumes a 1 % incidence of homozygous recessives in the population and that 

 10% of these are chronically incapacitated with a reduction in fecundity of 50% (s = 0.05). 



