Sexual selection

“ With respect to the slight individual differences which are common, in a greater or less degree, to all the members of the same species, we have every reason to believe that they are by far the most important for the work of selection. Secondary sexual characters are eminently liable to vary, both with animals in a state of nature and under domestication.187 There is also reason to believe, as we have seen in our eighth chapter, that variations are more apt to occur in the male than in the female sex. All these contingencies are highly favourable for sexual selection. ”

“ The reason of my being so much interested just at present about sexual selection is, that I have almost resolved to publish a little essay on the origin of Mankind, and I still strongly think (though I failed to convince you, and this, to me, is the heaviest blow possible) that sexual selection has been the main agent in forming the races of man. ”

“ The theory of sexual selection is based upon the assumption that choice is exercised by the female, and this exercise of choice must go hand-in-hand with a corresponding development of the critical faculty in regard to the comparative merits of different males, which again would involve a power of taking a liking, or a dislike, to any one of them. How are we to reconcile all this with that quiescent, waiting-to-be-spoken-to frame of mind which we assume to be that of the hen bird in regard to the cock, during the season of courtship? A decided preference should show itself in actions. ”

“ The best equipped males will thus crowd out the less well-equipped in the matter of reproduction, and thus the relevant characters will be increased and perfected through sexual selection. It is, of course, a necessary assumption that these secondary sexual characters may be transmitted to the female, although perhaps in rudimentary form. ”

“ In either case sexual selection must have acted on the male when he had to compete with rivals for the possession of the female; and in both cases the characters thus acquired have been transmitted to both sexes and all ages. But these characters, if acquired by the males when adult, may have been transmitted at first to the adults alone, and at some subsequent period transferred to the young. ”

“ Now, why should one sex enjoy such comparative immunity from the results of practices that are producing such disastrous effects upon the personal appearance of the other? The answer, I take it, is to be found in a cause which Mr. Darwin claims to have been the chief factor in all cases where the purely ornamental qualities of a species are concerned—sexual selection. ”

“ To sum up on the means through which, as far as we can judge, sexual selection has led to the development of secondary sexual characters. It has been shewn that the largest number of vigorous offspring will be reared from the pairing of the strongest and best-armed males, victorious in contests over other males, with the most vigorous and best-nourished females, which are the first to breed in the spring. ”

“ Going beyond Wallace, Groos denies conscious sexual selection, but, as he points out, this by no means involves the denial of unconscious selection in the sense that "the female is most easily won by the male who most strongly excites her sexual instincts." ”

“ In such cases it may be suggested with more plausibility, that there has been a double or mutual process of sexual selection; the more vigorous and precocious females selecting the more attractive and vigorous males, the latter rejecting all except the more attractive females. But from what we know of the habits of animals, this view is hardly probable, for the male is generally eager to pair with any female. It is more probable that the ornaments common to both sexes were acquired by one sex, generally the male, and then transmitted to the offspring of both sexes. ”

“ It is a safer conclusion that, as vocal and instrumental organs are of special service only to the males during their courtship, these organs were developed through sexual selection and their constant use in that sex alone—the successive variations and the effects of use having been from the first more or less limited in transmission to the male offspring. ”

“ And as no other function can be assigned to it than that of charming the female when it is erected in courtship, the peculiarity of form and mechanism which it presents—like the elaboration of patterns in cases where colour only is concerned—virtually compels us to recognise in sexual selection the only conceivable cause of its production. ”

“ It is clear then that, granting the biological premises of our author that the lowest sexual organisms are virtually female and that in the hermaphrodites the female element predominates; that in the earliest forms of bi-sexuality the fertilising or male element was merely an offshoot of the female trunk and that this offshoot develops, mainly by means of sexual selection on the part of the female, into an organism similar to the latter; that not until we reach the higher vertebrates, the birds and the mammals, do we find any traces of male superiority ”

“ The process of the development of the male sex is by means of the sexual selection of the female. From being a mere fertilising agent, gradually, as evolution proceeds, it assumes the form and characteristics of an independent organism like the original female trunk organism. But the latter continues to maintain its supremacy in the life of the species, by means chiefly of sexual selection, until the human period, i.e. more or less (!) , for Mr Ward is bound to admit signs of male superiority in the higher vertebrates—viz. birds and mammals. ”

“ With primeval man under the favourable conditions just stated, and with those savages who at the present time enter into any marriage tie, sexual selection has probably acted in the following manner, subject to greater or less interference from female infanticide, early betrothals, etc. ”

“ By sexual selection we mean union by choice among males and females. In the vertebrates, the female chooses much more commonly than the male, the latter being more disposed to pair with all the females than the females with all the males. ”

“ If he accepts these conclusions, he may, I think, safely extend them to mankind; but it would be superfluous here to repeat what I have so lately said on the manner in which sexual selection has apparently acted on both the male and female side, causing the two sexes of man to differ in body and mind, and the several races to differ from each other in various characters, as well as from their ancient and lowly-organised progenitors. ”

“ Darwin himself believed thoroughly in what he called sexual selection. It is the essence of this idea that the males and females have grown unlike, more technically have developed secondary sexual characters, through the choice of the mating pair. ”

“ We are, however, here concerned only with sexual selection. This depends on the advantage which certain individuals have over others of the same sex and species solely in respect of reproduction. When, as in the cases above mentioned, the two sexes differ in structure in relation to different habits of life, they have no doubt been modified through natural selection, and by inheritance limited to one and the same sex. So again the primary sexual organs, and those for nourishing or protecting the young, come under the same influence ”

“ Hence we may conclude, that it is the object of the male to induce the female to pair with him, and for this purpose he tries to excite or charm her in various ways; and this is the opinion of all those who have carefully studied the habits of living birds. But there remains a question which has an all important bearing on sexual selection, namely, does every male of the same species equally excite and attract the female? ”

“ As variations which give to the male a better chance of conquering other males, or of finding, securing, or charming the opposite sex, would, if they happened to arise in the female, be of no service to her, they would not be preserved in her through sexual selection. We have also good evidence with domesticated animals, that variations of all kinds are, if not carefully selected, soon lost through intercrossing and accidental deaths. ”