474 THE HISTORY OF BIOLOGY 



and maintains that even amongst wild tribes only social virtues are respected. 

 He has no interest in individual soul-life — a lack of interest which he like- 

 wise shared with many scientists of his age and which involves him in 

 anthropomorphitic interpretations of purely instinctive phenomena, not to 

 mention the credulity that he shows towards the statements of other owners 

 of domestic animals regarding the purely human intelligence manifested by 

 their four-legged friends. As to the time and place of the first appearance of 

 the human race he expresses himself with a certain amount of caution, as he 

 does also in regard to the racial problem. 



Sexual selection 

 By far the greater portion of the work under discussion deals, however, 

 with another question — namely, the origin of the secondary sexual char- 

 acters. To these Darwin considers that the theory of natural selection 

 in the ordinary sense cannot be applied; he does not believe he can use it 

 to explain the origin of such features as the horns of the stag-beetle and 

 the males of other coleopters, the brilliant coloration of male butterflies, 

 the cock's-comb, the horns of the stag, and other similar characteristics. 

 He considers rather that these features have arisen as a result of special 

 sexual selection; the males have competed for the favour of the females, 

 and the most attractive or the strongest have gone off victorious and been 

 allowed to propagate and to transmit their characteristics by inheritance 

 to their offspring. He finds proofs of this in the playing and the fighting 

 that takes place between the males in the mating-season; the butterflies' 

 sport in the air, the combats of cocks and stags, the song of the nightingale 

 and the lark, the play of the wood-grouse, and the stately mating-dance of 

 the cock of the rock. But it is not only the male qualities, but also certain 

 common characteristics that he attributes to this kind of selection, as for 

 instance the coloration of the butterflies, which he believes to have arisen 

 owing to the females' also having acquired their share of the inheritance 

 of sexual selection. This doctrine of sexual selection was rejected even earlier 

 than the general theory of selection and is nowadays embraced by hardly any 

 true scientists, although popular literature shows traces of it. What really 

 brought about its rejection is the increased knowledge of internal secretion 

 and the connexion of the secondary sexual characters with it; both sexual 

 coloration and mating-play have their explanation in this. That Darwin 

 knew nothing of this cannot, of course, be laid at his door, but even apart 

 from this fact, the sexual-selection theory certainly gives strong evidence of 

 his tendency to attribute without criticism purely human ideas to the ani- 

 mal kingdom, to believe in "beauty competitions" among butterflies and 

 beetles, fishes and newts, or that grasshoppers and crickets have a musical 

 ear. It has also been pointed out that it is purely physical strength and not 

 beauty at all that makes cocks and stags successful with the females, 



