490 THE DESCENT OP MAN. 



the same family,'" should for any special purpose, have been ren- 

 dered pure white and thus made conspicuous to their enemies; 

 or that the adults of one of these two species should have been 

 specially rendered white during the winter in a country which is 

 never covered with snow. On the other hand we have good rea- 

 son to believe that whiteness has been gained by many birds as a 

 sexual ornament. We may therefore conclude that some early 

 progenitor of the Ardea asha and the Buphus acquired a white 

 plumage for nuptial purposes, and transmitted this color to their 

 young; so that the young and the old became white like certain 

 existing egrets; and that the whiteness was afterwards retained 

 by the young, whilst it was exchanged by the adults for more 

 strongly-pronounced tints. But if we could look still further back 

 to the still earlier progenitors of these two species, we should 

 probably see the adults dark-colored. I infer that this v/ould be 

 the case, from the analogy of many other birds, which are dark 

 whilst young, and when adult are white; and more especially 

 from the case of the Ardea gularis, the colors of which are the 

 reverse of those of A. asha, for the young are dark-colored and 

 the adults white, the young having retained a former state of 

 plumage. It appears therefore that, during a long lino of descent, 

 the adult progenitors of the Ardea asha, the Buphus, and of some 

 allies, have ■ undergone the following changes of color: first, a 

 dark shade; secondly, pure white; and thirdly, owing to another 

 change of fashion (if I may so express myself) , their present slaty, 

 reddish, or golden-buff tints. These successive changes are in- 

 telligible only on the principle of novelty having been admired by 

 birds for its own sake. 



Several writers have objected to the whole theory of sexual 

 selection, by assuming that with animals and savages the taste 

 of the female for certain colors or other ornaments would not 

 remain constant for many generations; that first one color and 

 then another would be admired, and consequently that no per- 

 manent effect could be produced. We may admit that taste Is 

 fluctuating, but it is not quite arbitrary. It depends much on 

 habit, as we see in mankind; and we may infer that this would 

 hold good with birds and other animals. Even in our own dress, 

 the general character lasts long, and the changes are to a certain 

 extent graduated. Abundant evidence will be given in two places 

 in a future chapter, that savages of many races have admired for 

 many generations the same cicatrices on the skin, the same hlde- 



"« The young of Ardea rufescens and A. coerulea of the U. States 

 are likewise white, the adults being colored in accordance with their 

 specific names. Audubon ('Ornith. Biography,' vol. ili. p. 416; vol. iv. 

 p. 58) seems rather pleased at the thouglil that this remarkable change 

 of plumage will greatly "disconcert the systematists." 



