64 ADAPTATION AND PROGRESS 



outcome of the process of natural selection. In this discussion 

 Darwin pays tribute to Herbert Spencer and agrees with his 

 doctrine of use-inheritance taken from Lamarck. Man's 

 development, he holds, is in every case homologous with that of 

 the lower orders.^ 



In discussing the rate of increase in population our author fol- 

 lows Mai thus rather than Spencer, holding that " there is reason 

 to suspect . . . that the reproductive power is actually less in 

 barbarous than in civilized races." ^ Mai thus is criticized for not 

 giving sufficient emphasis to infanticide as a check among 

 primitive people. 



Passive adaptation which gave man the prehensile thumb, 

 erect posture and added brain capacity, is shown to have been the 

 one supreme factor in making possible those later differentiations 

 which are the crowning glory of the human race.^ 



In conclusion, he says: — 



As all animals tend to multiply beyond their means of subsistence, so it 

 must have been with the progenitors of man and this will inevitably have led 

 to a struggle for existence and to natural selection. This latter process will 

 have been greatly aided by the inherited effects of the increased use of parts; 

 these two processes incessantly reacting on each other. It appears, also, as 

 we shaU hereafter see, that various unimportant characters have been 

 acquired by man through sexual selection. An unexplained residuum of 

 change, perhaps a large one, must be left to the assumed uniform action of 

 those unknown agencies which occasionally induce strongly-marked and 

 abrupt deviations of structure in our domestic productions. 



With strictly social animals, natural selection sometimes acts indirectly 

 on the individual, through the preservation of variations which are beneficial 

 only to the community. A community, including a large number of well- 

 endowed individuals, increases in number and is victorious over other and 

 less well-endowed communities; although each separate member may gain 

 no advantage over the other members of the same community.* 



In Chapter V of the Descent of Man we find developed the 

 doctrine phrased in this paper as active material adaptation. 

 Following Wallace our author shows how important was the 



^ Ch. IV. It is noteworthy that both Wallace and Weismann differed from 

 Darwin as to the explanation of the evolution of mental and moral faculties by 

 natural selection. Wallace, Darwinism, p. 461. 



2 Descent of Man, p. 127. 



» Ihid., ch. IV. * Ihid., p. 149. 



