I don't think people 4000 years ago had access to the feminist writing developed in the past few decades, so they do not have the same basis for understanding gender. People didn't even speak any modern language, so it is a rather extraordinary claim to suggest that they would understand any academic sociological, political, scientific concept in exactly the same terms as we do.
I would say that modern feminist writing is drawing a conclusion about gender from the same basis of understanding as the ancients, though not necessarily the same conclusions they drew.
And I'm not claiming an understanding in exactly the same terms we understand it. I'm saying I wouldn't be surprised of their approach to the question was, as a society, functionally similar to ours, regardless of the terms they used.
And I question the whole premise that we've recently discovered something objectively (scientifically) true about gender that was unknown to the ancients and changes everything we thought we knew about it.
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In fact, I'd say it's probably the other way around. We've inherited our gender roles in society from the ancients via thousands of years of tradition and social evolution. It seems pretty clear that the ancients had a good grasp of the physical disparities between the two sexes, and evolved gender roles in society accordingly. Hence the taboo against striking a woman, the emergence of chivalry as a moral framework, and the convention against sending women into combat.
Not that these stereotypical gender roles are necessarily good things. But you can see a link back to biological reality in them. Hell, even customs like the chador make sense, if you couple awareness of the biological reality with a particularly cynical view of the depravity of human nature.
Modern "science" seems to be more concerned with denying the biological reality, or imagining that gender roles in society can and should be entirely decoupled from it. Up to and including gender roles that are entirely and directly based on that biological reality. Competitive sports leagues, for example.
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Anyway, I'm less interested in the science of terminology, and more interested in the science of human rights.
Do you have any (non-wikipedia) citations of scientific literature that describes what rights transsexuals are entitled to, that they don't already enjoy?