Origin of Species Variorum

attended to birds in confinement well know that they often take individual preferences and dislikes: thus Sir R. Heron has described how one pied peacock was eminently attractive to all his hen birds. It may appear childish to attribute any effect to such apparently weak means: I cannot here enter on the .. necessary details; but if man can in a short time give elegant carriage and beauty to his bantams, according to his standard of beauty, I can see no good reason to doubt that female birds, by selecting, during thousands of generations, the most melodious or beautiful males, according to their standard of beauty, might produce a marked effect. ... Some well-known laws, with respect to the plumage of male and female birds, in comparison with the plumage of the young, can be explained through the action of sexual selection ↑ on variations occurring at different ages, and being transmitted to the males alone or to both sexes at a corresponding age; but I have not space here to enter on this subject.

Thus it is, as I believe, that when the males and females of any animal have the same general habits of life, but differ in structure, colour, or ornament, such differences have been mainly caused by sexual selection: that is, by individual males having had, in successive generations, some slight advantage over other males, in their weapons, means of defence, or charms; and having transmitted these advantages to their male offspring. Yet, I would not wish to attribute all such sexual differences to this agency: for we see peculiarities arising and becoming attached to the male sex in our domestic animals (as the greater development of the wattle in male carrier-pigeons, horn-like protuberances in certain fowls, &c.), which are in no way useful. We see analogous cases under nature,— for instance, the tuft of hair on the breast of the turkey-cock, which cannot be useful and can hardly be orna- mental;—