OCR Text |
Show 294 DARWINISM CIIAl'. train that has led to the broadening of the feath_ers at the ends, and the consequent production of the magmficent eyespots which now form its crowning ornament. The display of these plumes will result. from the_ same causes which led to their production. Just 111 proportwn as the feathers themselves increased in length and abundance, the skin-muscles which serve to elevate them would increase also i and the nervous development as well as the supply of blood to these parts being at a maximum, the erection of the plume:-; would become a habit at all periods of nervous or sexual excitement. The display of the plumes, like the existence of the plumes themselves, would be the chief external indication of the maturity and vigour of the malo, and would, therefore, be necessarily attractive to the female. Wo have, thus, no reason for imputing to her any of those resthetic emotions which are excited in us, by the beauty of form, colour, all(l pattern of these plumes; or the still more improbable msthctic tastes, which would cause her to choose her mate on account of minute differences in their forms, colours, or patterns. As co-operating causes in the production of accessory ornamental plumes, I have elsewhere suggested 1 that crm;ts and other erectile feathers may have been useful in making the bird more formidable in appearance, and thus serving to frighten away enemies; while long tail or wing feathers might serve to distract the aim of a bird of prey. But though this might be of some usc in the earlier stages of their development, it is probably of little importance compared with the vigour and pugnacity of which the plumes arc the indica,tion, and which enable most of their possessors to defend themselves against tho enemies which are dangerous to weaker and more timid birds. Even the tiny humming-birds arc said to attack birds of prey that approach too ncar to their JJ c.'Ls. The Effect of Female Pr·efer·ence will be Neutmlised by N atuml Selection. The various facts and arguments now briefly set forLh, afford an explanation of the phenomena of male ornament, 1 Trop'ical Nat1t1·e, p. 209. In Chapter V of this work th e view. here advocated were first set forth, and the reader is referred there for further details. x COLOURS AND ORNAMENTS CHARACTERISTIC OF SEX 295 as being due to tho general laws of growth and deYclopmen~, and make it unnecessary to call to our aid so hypothetiCal a cause as the cumulative action of female preference. There. remains, however, a general argument, arising from the actwn of 11atural s lcction itself, which renders it almost inconceivable that female preference could have been effective in the way suggested; while the same argument strongly supports the view here set forth. Natural selection, as we have seen in our earlier chapters, acts perpetually and on an enormous scale in weeding out the "unfit" at every stage of existence, and preserving only those which arc in all respects the very best. Each year, only a small percentage of young birds survive to take the place of the old birds which die; and tho survivors will be those which are best able to maintain existence from the egg onwards, an important factor being that their parents should be well able to feed and protect them, while they themselves must in turn be equally able to feed and protect their own offspring. Now this extremely rigid action of natural selection must render any attempt to select mere ornamcnt·uttcrly nugatory, unless the most ornamented always coincide with "the fittest" in every other respect ; while, if they do so coincide, then any selection of ornament is altogether superfluous. If the most brightly coloured and fullest plumaged males arc not the most healthy and vigorous, have not the best instincts for the proper construction and concealment of the nest, and for the care and protection of the young, they arc certainly not the fittest, and will not survive, or be the pa-rents of survivors. If, on the other hand, there is generally this correlation-if, n,s has been here argued, ornament is the natuml product and direct outcome of superabundant health and vigour, then no other mode of selection is needed to account for tho presence of such ornament. The action of natural selection docs not indeed disprove the existence of female selection of ornament as ornament, but it renders it entirely ineffective; and as the direct evidence for any such female selection is almost nil, while the objections to it are certainly weighty, there can be no longer any reason for upholding a theory which was provisionally useful in calling attention to a most curious and suggestive body of facts, but which is now no longer tenable. |