This is one of those questions to which I always have to answer "I just don't know". For a long time, I believed gender was completely artificial; however, I've met many people who felt for many years so certain that they were assigned the wrong gender that I've had to wonder if it is in fact "a thing" after all. Just to confuse things, what's true for one person may not be true for another - while one person might be male, female or even both, another might not have a gender at all.

In other words: I have absolutely no idea.

In both ancient India, and the indigenous people of this continent realized that both gender and "sexual orientation" are on a spectrum, and they just accepted this in their societies. A person could be at one end or the other of that spectrum, or somewhere in between. People were allowed to be whomever they identified without prejudice or discrimination. Then in both cases, England came along and ruined everything. I imagine their self-righteous Christianity didn't help.

Yes gender is a thing. Just because a man can make himself look like a woman doesn’t make him a woman because he won’t be able to carry a child for nine months in a womb like a woman. The same goes for a woman who makes herself look like a man but she will not produce sperm to impregnate a real woman. If some people are so fixated on changing their gender then they should study frogs that are capable of actually changing their gender and make a drug or something that gives the same results as when these frogs change their gender.

I think it is a thing although I do get confused by it a lot. It is based on sex but as there are only two of those it isn't really. The best I can describe it is that it is based on predetermined make up of the mind since it does not seem to change from the point of first self expressed sexuality of the child, seems that we are not born blanks when it comes to sexuality. I know that for as long as I can remember I thought of myself as male and interested in the opposite sex even when I didn't know why, I suspect that this is no different for any human being regardless of which sex they identify as or which sex or sexes they are interested in.