Race is, however, physically evident.
Not really. Humans have intermixed for thousands of years, and the genetic boundaries between, say, Africans and Arabs and Whites and Asians aren't really well-defined. Most of us have a cut-off point in our own mind of what an African person looks like, but it's entirely invented and not actually based on well-defined genetic traits.
On the same token, if someone has tits, dresses female, talks characteristically 'female', but also has a richard, isn't it physically evident that they're transgender?
