Agree with BlindYeo "Brain biology is such a red herring, I don't care if there is some difference in their brain that makes them think they're a woman. If I am competing against a TIM in sport their lady brain is of no relevance to me. It's their superior size and strength that makes things unfair. Having a pink brain, even if there were such a thing, doesn't suddenly make pregnancy, abortion, breastfeeding, menstruation or endometriosis an issue for them. So they still don't merit the same biological category as me."
The brains thing is a massive red herring. I am female, and was a girl and am now a woman. Based on when I was born people spotting a vulva and saying "it's a girl", then socialising me as such (clothes, treatment) and then at puberty I grew breasts and got periods and then it was time for an additional layer of socialisation of my place as a member of the sex class.
It is all about biology and how people treat you, for me the way men treated me after puberty affected me particularly strongly.
This brain stuff is what? what even is it. Sex has been about biology and gender role. The sex is observed and the gender role is enforced. That is it.
What even would this pink brain stuff mean? Is it flowers and kittens? Deference? Personality of a laydee? A desire to be sexually dominated? Liking of the trappings of femininity? Many people feel that their bodies are wrong, it doesn't mean that they literally ARE.
Massive massive red herring.