rosesandflowers: It's a modern translation to describe one of the original genders of ancient Native Americans. Two genders has always been a ridiculously simple construct and so the Native Americans had more - 7, I believe, though I might be wrong. Unlike most ancient societies, which almost always had terms for genderfluidity, they were held in great esteem and seen as very special by the Native American people.
So you're not just ignorant about modern identities - but of history and other culture! wink Good going.
Let's have a think about this one. One can take two perspectives on a given culture's belief system - a kind of "internal one" (what do they say about their own beliefs) and an "external one" (what would an anthropologist/sociologist say about the work this particular belief system is doing in providing a kind of social glue to keep that society together and working smoothly). You're adopting an internal viewpoint - "they say this about themselves and who am I to criticise", whereas one can equally say "they say this about themselves, and I don't share that belief set, but it's interesting to ask where it comes from and why."
I've had many a chat with a friend who's a professor of anthropology about this one. She says that gender roles (old style social sciences meaning of gender as "set of behaviours, clothing, occupations, etc. deemed by a society to be appropriate to one biological sex or the other") are ubiquitous. But they are interesting. They can be either variable across cultures (Medieval Iceland: weaving is a woman's job; Medieval England: weaving is a man's job), or fairly constant. Where they are fairly constant, there's also usually a fairly obvious reason rooted in biological function. So across almost all cultures, looking after small children falls to women, because only women lactate. Handling heavy draft animals, big game hunting (not small game - both sexes typically do this to a lesser or greater degree), being a warrior fall to men because they are physically bigger, stronger and faster on average.
Next comes the society's attitude to transgressing gender roles (in this old-school social sciences sense of "roles attributed by society to one sex or the other"). Some are what she calls "flexible" (she is very insistent that fluid is the wrong word), whereas other societies are "rigid" and have strong sanctions against transgressing gender roles. I guess it's this situation: a widow needs her fields ploughed, borrows her neighbour's ox, and does it herself. Is the reaction "She's a bit of an odd-ball, but needs must I suppose" or is it "unnatural woman, burn the witch"?
Now for where this intersects with trans issues. Third genders/two spirit people/allowed cross dressing like Bacha Posh or Sworn Virgins are much more common as a sociological phenomenon in societies with a rigid attitude to gender boundaries. What they seem to do is provide a safety valve for people who just don't fit. Whereas a society with a flexible attitude to gender can say "well, Freda's just a bit odd, but it's not really doing anyone any harm", a rigid society says "Freda can only do this if she becomes Fred."
So for an anthropologist, the observation that some (not all by any means) Native American cultures have Two Spirit people isn't evidence that there really are people out there with two spirits, it's simply evidence that this is a belief set which works for this society in terms of keeping things ticking over and allowing for fairly rigid gender (sex-role meaning of gender) boundaries to be maintained while giving an escape route to the people really made unhappy by these roles.