Crossdressing a lifestyle choice or genetic?

[ElaineB]

All normal brains are built in exactly the same way with the same number of folds arranged in the same pattern in the same places.

I think you are carrying your argument too far. It has been proven beyond doubt that brain structure is partly determined by heredity and not everyone has the same basic brain. Twins separated at birth tend to have the same personality traits. Those traits can also run in families even in clear cases where they could not have been taught ... my own case is one such. My father and I (and most of the men in that side of my family) have very similar personalities but he did not raise me. Then there are the many studies tracing conditions like schizophrenia, ADHD, bipolarity through families ... which show that some of those clearly are linked to genes.

So it is quite conceivable that there are such inborn differences between male and female brains, even though it is hard to separate those differences from the ones that develop from the influence of sex hormones.

I was referring specifically to the genetic conditions raised by Batty which are abnormal because they are not present in the population in general. I use the word for its technical meaning not to infer any diminutive aspect about the conditions that result.

It is not that simple, though. Abnormal is only meaningful if there is a norm. While any one person might not carry the genes that predispose us to schizophrenia or addiction or whatever, it is very likely that all of us have some genes for some rare trait. So how can it be abnormal to have any of these? That would make everybody abnormal.

Because of that phrasing, I will venture to guess that you and some others may also be making a couple errors common in discussion of evolution. Evolution is not progress. It is just an extension of adaptation. It is also not monolithic. People can evolve to develop one trait while simultaneously remaining neutral in others or even devolving. So it really is just not true that all genes are still in our coding because they were advantageous, and it does not follow that a TG gene (if such exists) would have to provide some advantage somewhere. What biological or social advantage does it provide anybody to have earlobes? None that I can see, yet they exist anyway in some people and not others.

It is hard to justify a genetic cause to transgenderism based on our current understanding.

I do agree with this, but be careful not to go too far in the opposite direction.

What biological process creates men who want to behave as women and women who want to behave as men? And considering how men and women are supposed to behave is determined by ever-changing social values, how can this be accounted for by biological means?

I think that is the really meaty question in your argument and probably the point we should stick to.