THE EVOLUTION OE SEX. 



or overcome their less endowed competitors, he termed "sexual 

 selection." It is only fair, however, to state Mr. Darwin's case by- 

 direct quotation. 



Sexual selection ' ' depends on the advantage which certain indi- 

 viduals have over others of the same sex and species solely in respect 

 of reproduction." ... In cases where " the males have acquired their 

 present structure, not from being better fitted to survive in the struggle 

 for existence, but from having gained an advantage over other males, 

 and from having transmitted this advantage to their male offspring 

 alone, sexual selection must have come into action." . . . "A slight 

 degree of variability, leading to some advantage, however slight, in 

 reiterated deadly contests, would suffice for the work of sexual selec- 

 tion." ... So too, on the other hand, the females "have, by a long 

 selection of the more attractive males, added to their beauty or other 

 attractive qualities." . . . " If any man can in a short time give 

 elegant carriage and beauty to his bantams, according to his standard of 

 beauty, I can see no 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." 

 . . . "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 shown 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. If such females select the more attractive, and 

 at the same time vigorous males, they will rear a larger number of 

 offspring than the retarded females, which must pair with the less 

 vigorous and less attractive males. So it will be if the more vigor- 

 ous males select the more attractive, and at the same time healthy 

 and vigorous females; and this will especially hold good if the male 

 defends the female, and aids in providing food for the young. The 

 advantage thus gained by the more vigorous pairs in rearing a larger 

 number of offspring, has apparently sufficed to render sexual selec- 

 tion efficient." Another sentence from Darwin's first statement of 

 his position must, however, be added. " I would not wish," he says 

 in " The Origin of Species," "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, which we can not believe to 

 be either useful to the males in battle or attractive to the females." 

 Had Darwin seen another interpretation of the facts, he would thus 

 doubtless have given it frank recognition. 



