RETROSPECT AND PROSPECT 



energy, even for peacetime purposes, the problem will become very im- 

 portant of insuring that the human germ plasm— the all-important material 

 of which we are the temporary custodians— is effectively protected from 

 this additional and potent source of permanent contamination." 



The Future of Man. The physical future of man is, of course, the least 

 predictable of all of the topics discussed in this chapter. No new attempt 

 at prediction will be made, but rather the predictions of bolder authors 

 will be presented. Speculation has taken two broad alternative courses: on 

 the one hand, it has been assumed that the physical evolution of man has 

 reached an end point, but that much future evolution may be expected in 

 terms of the development of more efficient and peacable societies; others 

 have accepted the probability of further physical change, and they have 

 attempted to guess the character of these changes from past trends and 

 apparent selective forces now operative upon man. Some excellent papers 

 have been published upon the basis of the first alternative, but, as these 

 are primarily sociological in character, they are outside the scope of the 

 present work. 



Since the beginning of recorded history, predictions of the imminent 

 degeneration of mankind have been frequent. In our time, these are often 

 based upon the premise that man, through his benevolent institutions, has 

 arrested the action of natural selection. Mankind is burdened with the 

 unfit, and their genes, which would be eliminated by natural selection in 

 other species, are perpetuated. Hence biological disaster is inevitable. 

 This idea has not gone unchallenged. Many selective agencies are cur- 

 rently operative in man. An example may be mentioned. We live in a high- 

 speed, mechanized society, a thing unprecedented in history. Hence people 

 who are physically and mentally adapted to live in such a society should, 

 in the long run, have a selective advantage. This should put a premium 

 upon the ability to think quickly and accurately, and to make precise, 

 skillful movements. The effects of selection are obtained not onlv throuo;h 

 the difficulties of providing for a family in the absence of such abilities, 

 but also through the much higher accident rate among those who are mal- 

 adjusted to modern life. Accidents may "just happen," but every careful 

 study of accidents has indicated that they are caused, and they may prop- 

 erly be regarded as a highly eflFective source of selection pressure in mod- 

 ern society. Many other examples could be cited. The case was summarized 

 by Dobzhansky * as follows: "The eugenical Jeremiahs keep constantly 

 before our eyes the nightmare of human populations accumulating reces- 

 sive genes that produce pathological effects when homozygous. These 

 prophets of doom seem unaware . . . that wild species . . . fare no better 

 . . . than man . . . , yet life has not come to an end on this planet. The 

 eschatological cries proclaiming the failure of natural selection to operate 

 in human populations have more to do with political beliefs than with 

 scientific findings." 



A few writers have treated the future of man without Jeremiads. 



' Dobzhansky, Th., "Genetics and tlie Origin of Species," Lst Ed., Columbia Uni- 

 versity Press, 1937. 



334 



