CHAPTER XXIX 



SECONDARY SEXUAL CHARACTERS (continued) 



Theories of the Origin of Secondary Sexual Characters 



WHEN Darwin proposed his theory of natural selection in 

 1859 he brought forward also at the same time his theory of 

 sexual selection to account for the origin of secondary sexual 

 characters. "This form of selection depends not on a struggle 

 for existence in relation to other organic beings or to external 

 conditions, but on a struggle between the individuals of one sex, 

 generally the males, for the possession of the other sex. The 

 result is not death to the unsuccessful competitor, but few or no 

 offspring." Darwin believed that the secondary sexual char- 

 acters have arisen in either of two ways: either as a result of a 

 contest between the males that has led to the development of such 

 structures as the horns of the stag and the spur of the cock; 

 or as the result of selection by the females of the most adorned, 

 or brilliantly colored, or highly scented male individuals. This 

 latter form of selection has brought about the development of 

 such characters as the color, the ornaments, the song, and the 

 scent glands of the males. 



Of these two forms of sexual selection the first is merely an 

 extension of the principle of natural selection applied to the male 

 individuals of the same species ; while the second form of selec- 

 tion depends on the aesthetic taste of the females. 



In 1871 Darwin developed his theory of sexual selection much 

 more fully in his book on "The Descent of Man." Here he 

 appears at times to give the theory precedence over the theory 

 of natural selection itself, and attempts even to account for the 

 development of color and ornamentation, when it exists in both 

 sexes, by assuming that through the selection of the female it 



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