The Making of Species 
males, or those provided with the best weapons, 
have prevailed under nature, and have led to 
the improvement of the natural breed or 
species.” 
“With mammals,” says Darwin (oc. czz., 
p. 763), ‘“‘the male appears to win the female 
much more through the law of battle than 
through the display of his charms.” 
In the case of birds, however, feminine prefer- 
ence comes more into play. It is well known 
that cocks display their charms to the hens at 
the breeding season, and Darwin believed that 
the hen selected the most beautiful of her rival 
suitors. 
“Just as man,” he writes (p. 326 of Zhe 
Descent of Man, new edition, 1901), ‘‘can give 
beauty, according to his standard of taste, to his 
male poultry, or, more strictly, can modify the 
beauty originally acquired by the parent species, 
can give to the Sebright bantam a new and 
elegant plumage, an erect and peculiar carriage, 
so it appears that female birds in a state of 
nature have, by a long selection of the more 
attractive males, added to their beauty or other 
attractive qualities.” 
Thus the theory of sexual selection is based 
on three assumptions. Firstly, that there is in 
all species competition among the males for 
females with which to mate. Secondly, that 
this results in either “the law of battle” among 
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