CHAPTER VI 
DARWIN'S THEORY OF SEXUAL SELECTION 
SEXUAL SELECTION 
Tue theory of sexual selection was formulated by Darwin, 
even in the first edition of the “Origin of Species,” but was 
developed at much greater length in “The Descent of Man.” 
“This form of selection depends, not on a struggle for exist- 
ence in relation to other_organic beings or to external condi-_ 
“tions, but ona struggle between. the individuals. of one Sex, 
generally thé males, for the possession of the other sex. The 
result is not death to the ‘unsuccessful competitor, | _ but few or 
no~ offspring. Sexual selection is, therefore, less rigorous 
than natural_selection. Generally the most vigorous males, _ 
those which are best fitted for their place in nature, will leave 
most progeny. But in many cases victory depends, not so 
much on general vigor, as on having special weapons, con- 
fined to the male sex. A hornless stag or spurless cock 
would have a poor chance of leaving numerous offspring. 
Sexual selection, by always allowing the victor to breed, 
might surely give indomitable courage, length to the spur, 
and strength to the wing to strike in the spurred leg in 
nearly the same manner as the brutal cock-fighter by the 
careful selection of his best cocks.” It is important to no- 
tice that the theory of sexual selection is admittedly an 
extension of the selection principle into a new field. Having 
accounted for domesticated animals and plants by artificial 
selection, and for the adaptations of wild species by natural 
selection, there remained only to account for the second- 
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