The couple is only possible with a dimorphism, real but moderate. There must be a difference, especially of strength, in order for there to be a true union, that is to say subordination. A couple formed of equal elements, like a society of equal elements, would be in a state of permanent anarchy; two creatures suffice for anarchy, as for war. A couple formed of elements too unequal, would, by the crushing of the weaker, find itself reduced to tyrannized unity. Man and woman, as is the case with other primates and the carnivora (for most herbivora are polygamous) represent two sexes made to live united and to share jointly in the cares for their offspring. The state of couple, demanding a certain dimorphism, assures by it, its perpetuity. When the couple is dissolved, be it by polygamy or by promiscuity, as has happened among Mohammedans, and among Christians (a religion, long powerful, functions both as race and as milieu) the dimorphism is accentuated, each of the elements escapes, in some measure, the strict influence of the other sex. Likewise if, in consequence of identical education, the psychologic dimorphism is attenuated, even slightly--it never is attenuated more than slightly--or if physical games reduce a little the physical differences, the couple is less easily formed and grows less stable: hence adultery, divorces, excess of prostitution. In all monogamous society, prostitution is the strict consequence: it diminishes more or less in polygamous societies where the free women are rarer, it would only disappear completely in promiscuity, that is to say in universal prostitution.
Polygamy, apart from its indirect influence, has, by the internment of women, a direct one on the dimorphism. Set apart from the active life of the outer world, and even from the air and light, the female of the male polygamous human becomes whiter, whatever may have been her initial colour, fatter, heavier, and also more stupid and more addicted to all sorts of onanism. Among Indian Mussulmen the man and woman appear to belong to different species, the man being so tanned, and the woman so colourless. Shut-in prostitutes of the Occident also lose colour, and one would with difficulty recognize two sisters in the soft, bleached whore and the sun-reddened, hardy cow-girl. Woman's liberty also accentuates the dimorphism but by another process. Freed from the bridle of necessity, from the need of pleasing, woman escaped from the couple, exaggerates her feminism, she becomes again the female in excess, since it is in being more and more female that she has most chances of seducing the male, who is insensible to all other merit. And, inversely, a woman having man's education is, given equal beauty, less than any other a seductress.