I find all this talk of biological sex fascinating, but it doesn't always help in real life situations.
I've been asked to leave women-only space because of my failure to pass as a woman (I don't dress as a man, but I'm not exactly feminine-looking), and I don't know whether I could easily prove what sex I was assigned at birth. I frequently get called 'Sir' or am referred to as 'that chap' or similar.
Apparently some people can't always tell by looking whether someone is a man or a woman, or they just don't look closely. I wear women's clothes, but my body shape and size apparently suggest 'man' to many people. Even though my hair is shoulder length and I always carry a handbag. Maybe some people think I'm a trans woman. I've no idea.
Do people usually ask whether someone is a man or a woman? What kind of evidence would be acceptable, short of requiring someone to take off their underwear or provide a blood sample? Should I take my birth certificate with me if I want to access women-only spaces? Genuine question - it never occurred to me to worry before because I always assumed that if I say I'm a woman people will accept that. But from recent threads here, I'm no longer sure that's the case!