138 PHYSICAL BASIS OF CIVILIZATION 



own incompleteness, associated with a belief that the 

 qualities which are lacking can be found in the other. 

 Let it be remembered that this refers to mental and 

 aesthetic faculties only. 



Therefore, must an individual of one sex, on the 

 average, become mentally and aesthetically attract- 

 ive to the other, nearly in the same degree as he or 

 she possesses the special sex qualities of his or her 

 own sex. In other words, a man will be attractive 

 to women proportionate to his manliness, and a 

 woman attractive to men in proportion to her 

 womanliness in matters mental and aesthetic. In 

 this way has sexual selection aided natural selection 

 to increase and accentuate mental and aesthetic sex 

 traits in the human race, widening the difference 

 between the sexes. 



Now observe that these special sex qualities, 

 although, in the unending chain of cause and effect, 

 the remote results of reproductive activities, were 

 yet, from the very beginning, separate and inde- 

 pendent of the instinct and of the attraction origin- 

 ated by it. Note further, that from generation to 

 generation, under the influence of natural selection 

 and sexual selection, aided by the process which 

 Herbert Spencer calls "Multiplication of Effects," 

 this differentiation of the sexes has reached wider 

 and wider fields of human interest, in the realms of 

 actions, thoughts, and feelings, until in this age 

 there seems to remain hardly a thing, the reactions 

 of which on men do not more or less differ from its 



