THE STABILITY OF SPECIES 43 



to discover whether there is such a thing as sexual 

 selection — what we may call unconscious selection — 

 among human beings. His experiments tend to show 

 that there is. 



If we take a thousand married men whose stature is 

 not less than six feet, and a thousand also who are none 

 of them taller than 5 ft. 8 in., we shall find that the 

 average height of the wives of the former is greater 

 than that of the wives of the shorter men. 



If wild animals display a similar characteristic, it is 

 evident that to say that intercrossing swamps variation 

 and causes species to remain stable is not altogether 

 accurate ; for, if like select like as partners, we should 

 expect a number of races to rapidly arise, or, at any 

 rate, three races — a large, medium, and small one. So 

 far, however, as we can see, species display no such 

 tendency. We are therefore driven to the conclusion 

 either that there is among species in a state of nature 

 no tendency for like individuals to select like as their 

 partners, or, if there be such a tendency, there is some 

 force at work which counteracts it. 



It may be thought that the case of the peafowl in 

 the Lahore " Zoo " tends to show that among animals 

 it is dissimilarity, not similarity, that attracts, for the 

 coloured hens mate with white cocks in preference to 

 those like themselves. 



As a matter of fact the hens select the white 

 cocks, not because they are white, but because of 

 the strength of the sexual instincts of these latter. 

 The white cocks continually show off before the hens ; 

 the sexual desire is developed more highly in them 



