SEXUAL SELECTION, ASSORTATIVE MATING, ETC. 223 
the male in meeting the hazards of battle. The brilliant plumage 
of male birds, their powers of song and their instincts for display- 
ing their charms during courtship would probably long ago have 
been eliminated by natural selection had it not been for their 
appeal to the esthetic appreciation of the females. 
It is the part of Darwin’s theory of sexual selection which 
implies the potency of female choice which has incurred the 
greatest amount of adverse criticism. It is undeniable that in 
man, who is the only creature we are directly concerned with at 
present, female selection is capable of operating much as Darwin 
supposed it to act among less highly developed animals. How far 
this fact suffices to account for the differences in the appear- 
ance of the two sexes is a difficult problem. Some of these, such 
as the greater size and strength of man, his broader shoulders and 
the greater development of his pugnacious instincts may be in 
part the result of the “law of battle” during the early stages of his 
evolution, though they may be in part also the outcome of strug- 
gles which had no direct relation to mating. That sexual selection 
in the sense of preferential mating has played any important 
part in producing the relatively hairless condition of the human 
body or the development of beards in the male sex is open to grave 
doubt. In fact, it would be hazardous to assert that any particu- 
lar feature of either sex owes its existence wholly or even mainly 
to sexual selection. Nevertheless this factor can scarcely fail to 
have exerted some influence on racial development at all periods 
of human history. It is perhaps safe to say that unattractive 
women have always been at a discount, and that, notwithstanding 
their subordinate position among primitive peoples, women have 
in one way or another exercised a certain degree of choice in the 
selection of their mates. Undoubtedly the rigidity of tribal 
custom has greatly restricted the operation of sexual selection by 
women, and in many cases practically eliminated it altogether. 
Darwin, however, cites many illustrations of the fact that ‘with 
savages the women are not in quite so abject. a state in relation to 
marriage as has often been supposed. They can tempt the men 
whom they prefer, and can sometimes reject those whom they 
