44 THE GENETIC AND THE OPERATIVE EVIDENCE 



Darwin realized this difficulty and tried to meet it by another 

 assumption, viz, that the better endowed males would also be more 

 likely to have more offspring. How could this be made probable? 

 Darwin suggested that the strongest males would be in position to 

 mate with the first females to reach maturity, and if these were more 

 likely to have offspring, either because of maternal endowments that 

 made them also more prolific or because the earlier broods would have 

 a better chance of getting food, etc., then the successful competitor 

 would sooner or later impress his advantages on the race. 



At other times Darwin suggested that the exceptional vigor that 

 led to the greater development of the character in question would 

 itself be of value and through transmission to the offspring lead to 

 advance in the development of the other character in question. But 

 here the argument shifts to another field of inquiry and survival is 

 ascribed to greater vigor, while the secondary sexual character is carried 

 along in its wake as a sort of correlated effect. 



It will be conceded, I think, that such pleading does not help the 

 argument, but exposes rather its inherent weaknesses. There is, 

 however, a line of defense that is permissible. If monogamy is not the 

 rule, if the male captures or attracts several females and keeps a harem, 

 as do the fur seals and walruses, or rules a herd as does the bull, or has 

 a flock as does the cock, or mates more frequently with random females 

 than do some other males, then the advantage of his more developed 

 weapon might lead to more offspring. If it could be shown that such 

 intraspecific weapons prevail more frequently within polygamous spe- 

 cies, a fair argument for natural selection might be made. I do not know 

 whether such a census has been taken as yet, but it is true, I think, 

 that in most polygamous groups we find weapons of offense very highly 

 developed. The fur seal has a harem and the male is greater in size, 

 in strength, and in the development of his tusks than is the female. 

 Similarly for the walrus. The bull drives away rival bulls from the 

 herd until through age or injury, or through the development of a 

 better fighter, he is replaced. If the better endowment is due to a 

 genetic factor, we should expect natural selection to keep the race at 

 the highest possible level that variation supplies material for. If, then, 

 we confine the application of natural selection to cases of this sort, the 

 explanation is as valid as is the theory in other fields. Such a con- 

 clusion becomes weakened when an attempt is made to apply it to 

 other groups of animals in which it appears improbable that the 

 secondary sexual characters of the male have any obvious value as 

 organs of offense. There are families of beetles, for example, in which 

 the development of the horns of the male are as striking as are those of 

 the ram or the stag. The males of these beetles are not known to fight 

 with each other, nor are they polygamous. It may seem that we must 

 look here for some other explanation, which, if found, might suffice to 



