It is oppression that creates sex and not the contrary. The contrary would be to say that sex creates oppression, or to say that the cause (origin) of oppression is to be found in sex itself, in a natural division of the sexes preexisting (or outside of) society.
Monique WittigA materialist feminist approach to women's oppression destroys the idea that women are a 'natural group' . . . What the analysis accomplishes on the level of ideas, practice makes actual at the level of facts: by its very existence, lesbian society destroys the artificial (social) fact constituting women as a 'natural group.' A lesbian society pragmatically reveals that the division from men of which women have been the object is a political one . . .
Monique Wittig