Thank you for the excellent explanations, BowlofBabelFish.
Mumtobe I think you may have got a bit muddled by the reputation mumsnet has among trans activists, as being a place filled with mums whose only thought processes are about prams and Waitrose, who vote Tory and clutch their pearls and have 2.2 children conceived by pulling our flannelette nighties up round our waists in the dark for second-Saturday-in-the-month think-of-England sex in the missionary position, children who we are then worried will "catch the trans" from being exposed to brave and campaigning teachers like yourself.
In fact, as you may be beginning to realise, the truth is rather different. There are all sorts of people on here - mums, scientists, academics, former prostitutes (I know the term is a term of contention, but several exited prostitutes on here prefer that term to dressing up the harsh reality of what they experienced as "sex work"), civil servants, lawyers, business women, transwomen. There are straight women and lesbians and women who are bi, women who like make-up and fashion, women who never "perform femininity", women who vote Labour, Lib Dem, Tory, even Marxists.
When it comes to arguing about biology I'm afraid you're a bit out of your depth. I'm coming at this from 30+ years of university/research (admittedly in the physical rather than biological sciences) and there's a certain way people who are really on top of their material talk and explain things. I can tell that Bowl knows her stuff and you do not - you come across as an undergraduate who just got through her degree by the skin of her teeth and didn't actually understand a lot of what she was taught. Stick around though, and read back through Bowl's posts, and you might learn something.