Braaaiiinnnsss…

I don’t have a body; I am a body.
– Christopher Hitchens

You might like to believe otherwise, but all the evidence says we are no more and no less than physical beings. Our thoughts, feelings, and memories are nothing more (and yet so much more) than a few millilitres of chemicals squirting around our brains.

We have no control over this. What we are conscious of is the result of chemical activity that took place just a tiny fraction of a second earlier. The way I like to describe it, we don’t have free will, but our brains might.

This is some heavy shit to be throwing down, Twist; what does this have to do with crossdressing?! I hear you cry.

Well, a fellow blogger recently drew my attention to a report of opponents of sexual reassignment surgery cherry-picking data to suit their prejudices and declare that more research was needed […to support their opinions]. (I paraphrase in my own way, of course!)

Among the problems in the report (and whatever you do, do not read the comments at the end) was a conflation of sexuality and sexual identity. These are, of course, separate issues – but we can find some interesting brain stuff where they’re concerned.

It’s time to say hello to your hypothalamus.

Sexuality
Bailey & Zucker (1995) found 63% of gay men and women don’t conform to ‘gender behaviour’ as kids (vs 10-15% of straight people not conforming) – is this because of the way they are, or the way they were brought up?

Adler (1991) and Byne et al (2001) found a cluster of nerves in the hypothalamus was largest in straight men, smaller in gay men and slightly smaller in straight women (and this develops before birth). So it seems one’s sexuality is determined by brain development before we’re born.

Garcia-Falgueras & Swaab (2010) found environment doesn’t affect sexual identity or orientation.

So nature, not nurture, determines one’s sexual orientation – and it’s not an ‘either/or’ proposition – people can be more hetero-, or more homo-sexual (think of it as a range), or simply not interested (asexual; maybe 1% of people will identify as such). It’s not a matter of whether one prefers men or women or isn’t interested, but how much one prefers men or women or isn’t interested.

Despite almost a century of psychoanalytic and psychological speculation, there is no substantive evidence to support the suggestion that the nature of parenting or early childhood experiences play any role in the formation of a person’s fundamental heterosexual or homosexual orientation.
It would appear that sexual orientation is biological in nature, determined by a complex interplay of genetic factors and the early uterine environment.
Sexual orientation is therefore not a choice, though sexual behaviour clearly is.
– Royal College of Psychiatrists

Sex in the brain
To be clear: yes, there are size differences between the average male and female brains:

So when they ask “Are men and women’s brains different?”, you can unhesitatingly say, “yes”. And when they ask “And what does that mean for differences in how they think” you can say “Ah, now that’s a different issue”.

Joel et al (2015) conducted 1400 MRI scans of brains; and sure, there are some sex/gender differences in brain and behaviour. We have unique “mosaics” of features, some more common in females, some in males, and some common in both. Regardless of whether nature or nurture causes sex/gender differences in brain and behaviour, human brains cannot be categorized as ‘male’ or ‘female’.
(This has provoked some debate in letters to PNAS.)

Returning to the hypothalamus, Garcia-Falgueras & Swaab (2008) looked at the ‘interstitial nucleus of the anterior hypothalamus’ (INAH for short; it’s a bit in the middle at the back of the hypothalamus). They found the following:

• it’s larger and more elongated in men and more spherical in women;
• male-to-female transexuals have a similar INAH to women, as do castrated males;
• could the size of the INAH determined by testosterone?
• (But their study has been criticised for a small sample size and no study of different sub-types of transexuals.)

So, it seems there’s a bit of the brain that might well tell you what gender you are?

Swaab (2007) found sex differences in your body develop early in pregnancy (the first few months), but sexual differentiation of the brain occurs later in the second half of pregnancy. This explains why, for certain transexuals, you can expect to see ‘female brain structures’ in people who would otherwise be ‘male’ (for example).

So your body’s sex and your brain’s ‘gender’ can be different. Can we really divide people into two genders? Not if we use biology, it seems!

I don’t think anyone wanting to alter their appearance to match their gender should be seen as suffering from body dysmorphia. Being trans is the result of natural development processes in the womb, not anxiety.

Anxiety might come from lack of acceptance by others, though – but that’s something imposed from without, not something that comes from within. As the tragic case of David Reimer demonstrates, if you force someone to accept a sexual identity they do not have, it cannot end well.

If any part of your body knows what your identity is – well, it’s the brain!

*No, I’m not a neuroscientist, merely a geek and a nerd. This isn’t a complete and comprehensive run-down of brain research and sexuality and sexual identity, but is the best summary I can squeeze into less than a thousand words…