Tuesday I complained that the main argument against polygamy (men with multiple wives), that it creates more unmarried and hence unhappy  men, also argues for polyandry (women with multiple husbands), female prostitution, stronger punishment of wife affairs, and for forbidding women who never marry.  Many complained that I neglected to consider intrinsic gender asymmetries, which would induce more polygamy than polyandry, and more gays than lesbians.  Then there is Steven Landsburg:

Robin has it completely backward: When the wife of a 30 year old man (who is well past the prime age of violence) has an extramarital affair with an 18 year old, she is alleviating the problem, not contributing to it. Besides, most extramarital affairs do not deprive the husband of a long term sex partner.

Well there are several factors here to disentangle.  If the problem was just that some men never got any sex, well then yes women having more partners couldn’t hurt.  And if the problem was instead inequality in male sex, and if women had affairs with random men, then that couldn’t hurt either.  But if the problem is sexual inequality and if women are hypergamous, preferring the very best men, then we should expect it to be the same few, most likely married, men who repeatedly benefit from affairs.  An affair-occupied wife tends give less sex to her husband, which increases male sex inequality.

Now if you assume that women who want affairs, lesbian relations, or husband sharing would, if denied their favorite option, simply refuse to have sex with anyone, then allowing these things can’t reduce any guy’s sex. But allowing such things can make a difference when women would substitute other options.

So yes, banning polygamy could be part of a larger coherent strategy to reduce male sexual inequality, to resist natural female hypergamy.  But banning polygamy and also polyandry and prostitution, while allowing lesbian relations and preventing natural punishment of wife affairs, well that looks nothing like a coherent strategy to reduce male sexual inequality.  We should look elsewhere to explain our pattern of what we ban and what we allow.