Sex and gender identity is a modern issue. That was the first thing that came to my mind after reading the articles.
Is it because all the readings were written within the 20th and 21st centuries? Well, yes. That is a part of the reasons. Yet, what I want to express is that the issue itself is a reflection of an advanced human cognitive level.
It is because, we now think of individuals of significance, so that we pay attention to the differences within individuals. Thus medical and social studies of these differences came around and as a result, more and more of us noticed the importance of the existence of such differences. And all of these, depend on the fact that as a modern society, we human beings do not need to worry about keeping the breed of human species. Or else we would be forced back to the matrilineal society, where, you know the female took the charge! =P
Finding one's identity however, started way earlier, which can be traced back to Socrates. As Adrienne Rich mentioned, "we are studying the history of MAN" from that page on. In the course of history, we were seldom reminded of how the things were done by the males and yet, whenever the emperor or scientist was a woman, the writer seemed to be exciting as he/she thoughtlessly emphasized the fact that "SHE is a woman!"
So another question is raised. Given most of historical celebrities were "guys" and some of them were "gays", was there any transgenders/agenders that contributed greatly to the civilization of mankind? Or simply lesbians? Or other groups of people? Hell yes! They were the ones burned to death in the old stories!
Sex and gender identities are still controversial issues that needs time for us to reach a point of balance. It is hard for us to define everything and put everything in order within very short time. Lucky enough, we now noticed the importance of this kind of equilibrium and are working on it fighting for the rights of all individuals.