I'm saying that for a lot of people the "technical" definition of sex is really blurry. You could look at chromosomal sex, but even that can get weird. You hav

I'm saying that for a lot of people the "technical" definition of sex is really blurry. You could look at chromosomal sex, but even that can get weird. You have Kleinfelter's people (XXY), people who are XX but male because they have the SRY gene on one of their X chromosomes (XX Male/ de la Chappelle syndrome). You have people who have a Y chromosome but develop female because of androgen insensitivity. You can even have people that are chimeras that literally have both XX and XY genes in their body; there is a report of somebody who was 94% XY giving birth. There's a whole spectrum of intersex possibilities and ambiguous genitalia. Historically, doctors would pick which sex was surgically easiest to assign to the baby if their genitalia were ambiguous, and that was kind of disastrous because it's not just a societal construct and not just something you can flip at birth. Biologically speaking the presence or absence of SRY is kinda the closest thing to technical that you can get; that is the gene that causes the ovotestis to develop into testicles and start secreting testosterone and anti-mullerian hormone. Pretty much all the other changes in sexual development are keyed by levels of sex steroids. But as mentioned even if you have that, all kinds of things can cause that go weird; from your body not making testosterone, to it not being responded to correctly, to the womb environment introducing other chemicals that alter brain development. And especially with brain development, we don't really know how it works. There's studies that look at - if you take a baby mouse, and remove its ovaries/testes, and give it hormone X, then it acts this way towards other mice that looks more male or female. However, humans aren't mice and a lot of our sexual behaviors are pretty unique to the species (like face to face sex), and even then, our brains are way more complicated and complex. The difference between gender and orientation is almost impossible to see in an animal model (usually they look at things like, does the mouse try to mount female mice when they are receptive, does it exhibit lordosis posture, etc). > However this would be a massive overhaul to our entire society. Depends on the age involved but it really doesn't change anything the first few years. We'd have to get over the obsession with blue for boys and pink for girls and painting the rooms and gender reveal parties... but not much else. I mean historically (young) boys and girls wore basically the same clothes (just so more didn't need to be made/bought) and were treated the same because it really doesn't make any difference. Bathrooms are kinda the first thing but really what other difference is there? Especially before puberty? And let's not forget that even then, you're always going to have people who are ambiguous or fall between the cracks. Gender nonconforming, genderfluid, genderqueer - people who just don't feel one label fits them all the time. Even within the two-gender framework you have effeminate gay men, tomboys, and all sorts of other perfectly valid identities.