286 THE DESCENT OF MAN 



would probably bave disappeared; and, sucb as tbey are, 

 would bardly suffice to lead to effective sexual selection in 

 a state of nature. Nevertbeless, in the cases of some few 

 wild animals, as sbown in tbe supplement, tbe proportions 

 seem to fluctuate eitber during different seasons or in differ- 

 ent localities in a sufficient degree to lead to sucb selection. 

 For it sbould be observed tbat any advantage gained during 

 certain years or in certain localities by tbose males wbicb 

 were able to conquer their rivals, or were tbe most attractive 

 to tbe females, would probably be transmitted to tbe off- 

 spring, and would not subsequently be eliminated. During 

 tbe succeeding seasons, wben, from tbe equality of tbe sexes, 

 every male was able to procure a female, tbe stronger or 

 more attractive males previously produced would still have 

 at least as good a cbance of leaving offspring as tbe weaker 

 or less attractive. 



Polygamy. — Tbe practice of polygamy leads to tbe same 

 results as would follow from an actual inequality in tbe 

 number of tbe sexes ; for if eacb male secures two or more 

 females, many males cannot pair; and tbe latter assuredly 

 will be the weaker or less attractive individuals. Many 

 mammals and some few birds are polygamous, but with 

 animals belonging to the lower classes I have found no 

 evidence of this habit. The intellectual powers of sucb 

 animals are, perhaps, not sufficient to lead them to collect 

 and guard a harem of females. That some relation exists 

 between polygamy and the development of secondary sexual 

 characters appears nearly certain; and this supports tbe view 

 that a numerical preponderance of males would be eminently 

 favorable to tbe action of sexual selection. Nevertheless, 

 many animals wbicb are strictly monogamous, especially 

 birds, display strongly marked secondary sexual charac- 

 ters; while some few animals which are polygamous do not 

 have such characters. 



"We will first briefly run through tbe mammals, and then 

 turn to birds. Tbe gorilla seems to be polygamous, and the 



