Page - 101 - in The Origin of Species

SEXUAL SELECTION 101 If the numbers be wholly kept down by the causes just indi- cated, as will often have been the case, natural selection will be powerless in certain beneficial directions; but this is no valid objection to its efficiency at other times and in other ways; for we are far from having any reason to suppose that many species ever undergo modification and improvement at the same time in the same area. SEXUAL SELECTION. Inasmuch as peculiarities often appear under domestica- tion in one sex and become hereditarily attached to that sex, so no doubt it will be under nature. Thus it is rendered pos- sible for the two sexes to be modified through natural selec- tion in relation to different habits of life, as is sometimes the case ; or for one sex to be modified in relation to the other sex, as commonly occurs. This leads me to say a few words on what I have called Sexual Selection. This form of selec- tion depends, not on a struggle for existence in relation to other organic beings or to external conditions, but on a struggle between the individuals of one sex, generally the males, for the possession of the other sex. The result is not death to the unsuccessful competitor, but few or no offspring. Sexual selection is, therefore, less rigorous than natural se- lection. Generally, the most vigorous males, those which are best fitted for their places in nature, will leave most progeny. But in many cases, victory depends not so much on general vigour, as on having special weapons, confined to the male sex. A hornless stag or spurless cock would have a poor chance of leaving numerous offspring. Sexual selection, by always allowing the victor to breed, might surely give in- domitable courage, length to the spur, and strength to the wing to strike in the spurred leg, in nearly the same manner as does the brutal cockfighter by the careful selection of his best cocks. How low in the scale of nature the law of battle descends, I know not ; male alligators have been described as fighting, bellowing, and whirling round, like Indians in a war-dance, for the possession of the females: male salmons have been observed fighting all day long; male stag-beetles sometimes bear wounds from the huge mandibles of other