Here are some things I thought I understood about gender which turned out to be wrong.
- Myth: "Sex" and "gender" are the same thing – that is, The body's sex (biological reproductive role) is the same thing as the individual's gender.
- Myth: Gender identity is almost entirely socialized – that is, we're taught to be "girls" or "boys" by how we're treated. Your brain doesn't have an innate gender.
- Reality: It turns out that certain brain structures/wiring are different depending on whether you're male or female – and where gender identity differs from your biology, these differences correlate more closely to identity than to body type.
- There was a time when I didn't want this to be true, because I thought if brains were different then that would mean my brain would be different from a girl's brain, and that made me sad. It turns out that actually, it means my brain is more like a girl's brain and less like a boy's brain, which makes me happy. (It also fits with, and explains, decades of personal experience.)
- Myth: Gender and sex are either/or – you're either a boy or a girl; you can't be something in between.
- Reality: Gender is multidimensional, and each dimension is a continuum. There are strong correlations between the dimensions, but many individuals clearly do not fit the pattern. Even on a physical level, some individuals have ambiguous genitalia, or chromosomes that do not match their (natural) appearance.
- This is commonly known as the gender binary myth.
- More reading: gender/101 (on HTYP) has a more detailed explanation.
- Myth: Primary and secondary sexual characteristics are caused by genetics. XX chromosomes make you grow a female body and XY chromosomes make you grow a male body.
- Reality: Actually, they're determined entirely by hormones – which, normally, are determined by what type(s) of gonads you have (ovaries or testes), which are normally determined by developmental factors while in utero which are mostly (again) hormones, which are at some point usually determined by whether you have XX or XY chromosomes. (I'm probably explaining this wrong – but the point is that genetics only plays a role very early on in a long sequence of events, and a lot of things can happen to change the outcome.)
- There are some hormonal effects which are also hormonally reversible (switch to opposite hormones and it goes the other way), some which can be corrected surgically, and some which simply aren't fixable with current technology. See hormones for more details.