[amanaplanacanal]

This is clearly nonsense. You are taking about sex, not gender. There are a millions of baby girls born with Y chromosomes that aren't discovered until adolescence when they don't get their period, or even adulthood when they can't get pregnant.

See: Androgen Insensitivity Syndrome.

[mrec]

Well, "baby girls born with Y chromosomes" is very clearly begging the question, and I'm not sure where you're getting your "millions" figure from. Even the upper estimates of CAIS have it around 1 in 20,000 XY individuals, which would put global numbers in the order of 200,000.

[amanaplanacanal]

My mental arithmetic was bogus . The point is the same though. These are children who were assigned female at birth, their parents think they are girls, they think they are girls, and then in teens or adulthood they find out about the genetic issue. Calling them men seems ridiculous.

[mrec]

"Seems ridiculous" is a very subjective thing, though, and very dependent on context. It can seem ridiculous that a boxer with male physical advantage since puberty (i.e. 5-ARD) can beat the ** out of a female boxer while the world's media looks on and applauds, but here we are.

Personally I'm sympathetic to the idea that CAIS individuals should be a reasonable exception, i.e. they're still biologically male, but in most social contexts there's no obvious gain to treating them as such. I can see why many people have arrived at a hardline "XX or GTFO" position given the absolute state of activism on the other side, but yes, there's definitely room for nuance. On the other hand, obviously, testicular cancer doesn't care what you were "assigned at birth"; there is a fact of the matter, and it matters.

Appreciate the civil discussion, btw. It's a rarity in this subject.

[amanaplanacanal]

The problem with the genetic definition is that it means that nobody knows whether anyone is a man or a woman until they get tested. Nobody pre-genetic testing ever knew. Most people alive today don't know. And that's clearly not how society works, or ever has worked.

[mrec]

I think we're in severe danger of spiralling toward epistemology here, but there's a huge difference between "nobody knows" in the sense you're using it and "nobody has any idea". Society (or more broadly biology) doesn't need us to get it right 100% of the time; these are very, very rare conditions. Going off secondary sexual characteristics is going to get you the right answer as near as dammit every time, especially in premodern contexts, and society has always been happy to work with tiny or even not-so-tiny uncertainties. (Is that kid really mine? Is the accused really guilty?)

The way I see it, the sex binary is fundamentally about reproduction. It's why we can use the same concept for everything from pondweed to platypuses. All across nature, male=small gametes, female=large gametes. In humans that's driven (with the potential for things to go haywire occasionally, sure, but still driven) by the XX/XY system, so that strikes me as a reasonable thing to base a definition on.

Side note re "nobody knows whether anyone is a man or a woman until they get tested" - I'd say that giving birth or fathering a child is a pretty big clue. AFAIK the only cases where that doesn't line up perfectly with genetic sex relate to mosaicism, where I'll freely admit my intuition goes completely kablooie.

[amanaplanacanal]

Unfortunately, all the political noise is about gender rather than sex. Reproduction doesn't even ever the conversation. It's all about which restroom you should use or which sports team you should be on.