VALUE OF NEGATIVE EUGENICS 



Measures That Are Possible Are Decidedly Worth Taking but Must Not Be Ex- 

 pected to Cause Any Great Amount of Race Betterment Difficulties 

 in the Way of Constructive Eugenics' 



Edwin G. Conklin 

 Professor of Biology, Princeton University, Princeton, X . J. 



NO WE LL-informcd person doubts 

 that the i)rinciijlcs of heredity 

 and evolution ajjply to man as 

 well as to the lower organisms 

 and in spite of much controversy with 

 respect to the importance of natural 

 selection in evolution, I make bold to 

 assert that no other principle has yet 

 l)een suggested of equal importance 

 with this, and that the elimination of 

 the unfit affords not only the only 

 natural explanation for the existence of 

 fitness, but also the only means by 

 which breeders have been able to im- 

 prove domesticated animals and culti- 

 vated plants. The only possible control 

 which mankind can exercise over the 

 l^roduction of improved races of lower 

 organisms or of men lies in the elimina- 

 tion from reproduction of the less 

 favorable variations which are furnished 

 by nature. For it has become more 

 and more clear in recent years that, 

 while environment exercises a great in- 

 fluence over the development of the 

 individual, its influence on the germ 

 plasm or the hereditary characteristic 

 of the race is relatively slight and in 

 general is not of a definite or a specific 

 character. Probably environment may 

 under certain circumstances modify the 

 germ plasm, but there is no evidence 

 that good environment will i^roducc 

 good modifications, and bad environ- 

 ment bad modifications in this heredi- 

 tary substance. Consequently, the only 

 method which is left to man for improv- 

 ing races is found in sorting out the 

 favorable varieties from the unfavor- 

 able ones which are furnished by nature. 

 If the human race is to be permanently 

 improved in its inherited character- 



istics, there is no doubt lliat it must be 

 accomplished in the same way in which 

 man has made improvements in the 

 various races of domesticated animals 

 and cultivated plants. 



Fortunately, or unfortunately, the 

 methods which breeders use cannot be 

 rigidly applied in the case of man. It is 

 possible for l)reeders to eliminate from 

 reproduction all except the very best 

 stocks, and this is really essential if 

 evolution is to be guided in a definite 

 direction. If only the very worst are 

 eliminated in each generation, the 

 standard of a race is merely maintained, 

 but the more severe the elimination is, 

 the more does it become a directing 

 factor in evolution. This may be illus- 

 trated by a diagram in which \'ariations 

 in all directions are represented by lines 

 radiating from a central point. These 

 lines may be thought of as being indi- 

 vidually distinct, as in the "jjure line" 

 concept. If only those lines are blocked 

 which lead in one direction, the center 

 of radiation or "mode" would be but 

 slightly changed in successive genera- 

 tions. But if all lines are blocked l)ut 

 those which lead in one particular 

 direction, the mode will be rapidly 

 shifted in that direction in succeeding 

 generations. Therefore the value of 

 selection as a directing factor in evolu- 

 tion dejjcnds on its se\'erily. 



M.AINTAINlNll THE LliVKL 



In the case of man, however, even 

 the most enthusiastic eugenicists have 

 never ])roposcd to cut off from the 

 ])ossibility of reproduction all human 

 stocks except the very best, and if only 

 the verv worst stocks are thus elimin- 



' PajKT rc-ad lifforc the EuKinics Siction, American Assotiiition for the Study and Prevention 

 of Infant Mortality, Philadel])hia, Pa., November 11, 1915. 

 538 



