164 Rev. J. T. Gulick on Divergent Evolution 



ditions is necessary to divergent evolution. No suggestion is 

 given that through the action of sexual selection divergent 

 species may be produced that are not at all dependent on 

 differences in the environments, still there can be no doubt 

 that this was Darwin's view. Though he does not directly 

 discuss this problem in any passage I have been able to dis- 

 cover, he clearly expresses the opinion that the differences 

 between the different races of man, and between man and the 

 lower animals, are in no small degree due to sexual selection, 

 and he never speaks of difference in sexual selection as depend- 

 ing on difference in the environment, though, at the close of 

 the twentieth chapter of ' The Descent of Man,' he speaks of 

 sexual selection in man as having probably " exaggerated " 

 the " characteristic qualities " " which are of no service to " 

 the tribes and races that possess them. The differences, how- 

 ever, in the races of man are attributed to sexual selection, 

 not because of any lack of difference in their environments, 

 but because the characters in which they differ do not seem 

 to him to be related to the environment. The colour of the 

 skin, hair, and eyes, and the different forms of the head and 

 face, do not seem to be adapted to different conditions in the 

 environment, while they are undoubtedly occasions of attrac- 

 tion or aversion for those seeking partners. He has not, 

 however, shown whether the change of taste precedes the 

 change of form and colour or the reverse. Differences between 

 the sexes of the same species in secondary sexual characters 

 are for weighty reasons attributed to sexual selection ; but he 

 does not show how this divergence between the sexes leads to 

 the production of new species. This production of difference 

 of character between the sexes, being in no way dependent on 

 the prevention of crossing between the divergent sexes, must 

 be a wholly different process from the production of races and 

 species, which is absolutely dependent on prevention of cross- 

 ing between the divergent races and species. There is never- 

 theless every reason to believe that when the representatives 

 of a species capable of sexual selection are for many genera- 

 tions separated into groups that never cross, diversity of tastes 

 is one of the forms of diversity that inevitably arises ; but that 

 the psychological divergence is the cause of the other corre- 

 lated divergences is not so certain. The theory of divergence 

 in races because of divergence in the forms of sexual selection 

 seems to rest on the assumption that a psychological divergence 

 may be accumulated and rendered permanent in a new and 

 definite form without being subjected to selection ; but if this 

 is true of a psychological divergence, why may it not be true 

 of any form of divergence ? The difference in the ideals of 



