Prelapsarian, Postdiluvian

So, "race" is immutable, but "gender" is fluid?

That is almost literally bollocks.

To which the solution is an almost literal reading of something else: the Book of Genesis.

Human beings have always had the same two sexes, and they always will have.

But they are in fact all members of the same race, and time was when even the distinctions within that did not exist.

Ever since they have emerged, then those distinctions (not only the cultural responses to them, but the biological distinctions themselves) have been changing all the time.

Whereas the biological distinction between the two sexes, in itself and not only in terms of the cultural responses to it, has never changed, and it never will.

This is the basis, both of consolidating the gains of women in the face of their increasing erasure, and of consolidating the anti-racist movement in the face of the rise of the Alt-Right.

That basis is an almost literal reading of the Book of Genesis.