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 type of mankind 
to-day.”’—Karl Pearson, The Groundwork of Eugenics. Eugenics 
Laboratory Lecture Series, IT. 
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 
differ 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 codperate 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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