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 Malthus rather than Spencer, holding that “ there is reason 
to suspect . . . that the reproductive power is actually less in 
barbarous than in civilized races.”? Malthus 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 shall 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 
1 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. 
3 [bid., ch. IV. 4 Ibid., p. 149. 
