Morals: They’re nothing but a coded survival instinct! - Theodore Sturgeon

(...) my preoccupation in a larger sense is the optimum man. The question of establishing an internal ecology, where the optimum liver works with the optimum spleen and the optimum eyeball and so forth. Now, when you get to the mind — not the brain, but the optimum mind — then you have the whole inner space idea; my conviction is that there’s more room there than there is in outer space, in each individual human being. Love of course has a great deal to do with that, as a necessary coloration and adjunct to everything that we do — to love oneself, to love the parts of oneself, to love the interaction of the parts of oneself, and then the interaction of that whole organism with those of another person. Which is as good a definition of love as you can get, I think.

So it is easily seen that the sexual insignes are nothing in themselves, for any of them, in another time and place, might belong to both sexes, the other sex, or neither. In other words, a skirt does not make the social entity, woman. It takes a skirt plus a social attitude to do it.
But all through history, in virtually every culture and country, there has indeed been a “woman’s province” and a “man’s province,” and in most cases the differences between them have been exploited to fantastic, sometimes sickening extremes.
Why?

No man can rob successfully over a period of years without pleasing the people he robs.