CHAPTER VIII 



NATURAL SELECTION IN MAN 



"The conception of the destruction of the less fit as a beneficent 

 factor of human growth must become part of our mental atmosphere, 

 we must look upon it as a chief cause of the mental and physical 

 growth of mankind in the past, not as a blind and hostile natural force 

 carelessly crushing the single life, but as the source of all that we 

 value in the intellect and physique of the highest t5rpe of mankind 

 to-day." — Karl Pearson, The Groundwork of Eugenics. Eugenics 

 Laboratory Lecture Series, II. 



According to the Darwinian theory the evolution of life is 

 mainly the result of the operation of natural selection or the 

 preservation of favored races in the struggle for life. Opinions 

 diHer greatly concerning the extent to which natural selection 

 acts in the human species. Mr. Darwin considered the factors of 

 human evolution at some length in his Descent of Man and while 

 he has recognized the potency of sexual selection and the trans- 

 mission of the effects of use and disuse of parts, he lays great 

 stress upon natural selection, both in the preservation of the most 

 favored individuals and in the selection of the most efficient 

 social groups in intertribal and inter-racial conflict. "The early 

 progenitors of man," he says, ''must have tended, like all other 

 animals, to have increased beyond their means of sustenance; 

 they must, therefore, actually have been exposed to a struggle for 

 existence, and consequently to the rigid law of natural selection. 

 Beneficial variations of all kinds will thus, either occasionally or 

 habitually, have been preserved and injurious ones eliminated." 

 Mr. Darwin emphasizes the importance of variations in the direc- 

 tion of greater intelligence and the development of those social 

 instincts which lead mankind to cooperate for mutual defense. 

 These traits which are so characteristic of man would therefore 

 tend to be developed by natural selection during the entire course 

 of human development. 



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