According to the Book of Genesis, God first created man. Woman was not only an afterthought, but an amenity. For close on two thousand years this holy scripture was believed to justify her subordination and explain her inferiority; for even as a copy she was not a very good copy. There were differences. She was not one of His best efforts.
There is a line in an old folk song that runs: 'I called my donkey a horse gone wonky.' Throughout most of the literature dealing with the differences between the sexes there runs a subtle underlying assumption that woman is a man gone wonky; that woman is a distorted version of the original blueprint; that they are the norm and we are the deviation.
It might have been expected that when Darwin came along and wrote an entirely different account of the Descent of Man, this assumption would have been eradicated, for Darwin didn't believe she was an afterthought: he believed her origin was at least contemporaneous with man's. It should have led to some kind of breakthrough in the relationship between the sexes. But it didn't.
Almost at once men set about the congenial and fascinating task of working out an entirely new set of reasons why woman was manifestly inferior and irreversibly subordinate, and they have been happily engaged on this ever since. Instead of theology they use biology, and ethology, and primatology, but they use it to reach the same conclusions.
Elaine Morgan, The Descent of Woman, 1972