Me/gender misconceptions

Here are some things I thought I understood about gender which turned out to be wrong.

• 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: 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.
  • There are some hormonal effects which are hormonally reversible (switch to opposite hormones and it goes away), some which can be corrected surgically, and some which aren't fixable. Some things caused by hormones include:
    • Male hormones:
      • deeper voice: Not reversible by hormones; surgery is available but relatively new.
      • upper body muscles: reversible
      • If skeleton is still growing (not reversible except as noted):
        • skull bump in the back of the head
        • "Adam's apple": can be surgically reduced
        • certain facial skeletal features: can be surgically "feminized"
    • Female hormones:
      • more subcutaneous fat: reversible
        • This tends to make facial and body contours more "curvy" and lightens the skin tone in light-skinned people.
      • chest protrusions: irreversible except by surgery
      • If skeleton is still growing (not reversible):
        • wider hips
          • This is the other part of what makes female bodies more "curvy".
        • shorter stature