172 PROBLEMS OF EVOLUTION 



Sexual Selection plays the part of a skilled breeder. It mates 

 the best with the best, while Natural Selection only fixes a 

 survival line and lets those who come above it pair indiscriminately 

 obviously an inferior method. But while we admit this we 

 must bear in mind that in wild nature Sexual Selection is always 

 subordinate to Natural Selection. No characters are developed 

 by it that are injurious. Even the plumes of the peacock are 

 only a contrivance, so to put it, for increasing the vigour of the 

 species. For it is partly owing to these charms, if Darwin's 

 view is correct, that only the most vigorous males leave any 

 offspring behind them. 



Circum- In species where polygamy obtains, the males are very pug- 

 Bunder nac ' ous an ^ fight among one another. The cock of the farm- 

 which yard must depend for his supremacy mainly on his own prowess, 

 P Arises however much feminine admiration of his decorations may assist 

 him. But male pugnacity does not as a rule lead to polygamy. 

 For in most species of birds, the cocks are very fond of fighting 

 and the habit of pairing continues in spite of it. It may often 

 happen that no blood is shed and that the vanquished leaves the 

 field only half humbled and ready as soon as opportunity offers 

 to reassert his claim. This leads us to inquire as to the weapons 

 of offence. Among the polygamous species the males are 

 generally armed with spurs. The capercaillie (Tetrao urogallus) 

 and the blackcock (T. tetrix) have none, yet their fights are no 

 mere bloodless sparrings ; they have beaks and claws to fight 

 with. It is among the polygamists, with the doubtful exception 

 of the ruffs, that the fights are most desperate and most deadly. 

 It would seem that the pugnacious tendencies are somehow held 

 in check where pairing has become the rule. 



If we turn to mammals we find the facts are the same. Even 

 in what are accounted timid species, male pugnacity breaks out 

 in the breeding season. Male hares have been known to fight 

 till one of the combatants has been killed. But it is among the 

 polygamists that the fighting propensity is strongest. Every- 

 where there is the same tendency to masculine self-assertiveness, 

 but in most species an imperious necessity keeps it in check. 

 The young must be fed and defended ; that is the supreme need 



