riki said...
I am doing a PhD on the political and social implications of the brain sex theory of trans. My assessment is that there is certainly more evidence for that theory than for any other, but that it is far from "proven", and that many biological hypotheses have been falsified on the past (EG the HY antigen in the 70s and 80s). The psychological theories have very little evidence to support them.
I interviewed Dick Swaab, whose lab produced the BSTc research that is the strongest evidence for a neurological correlate for trans. It should be noted that one of the six MTF transsexual people in the original 1995 Zhou study had never transitioned, but insisted that they had a female gender identity. It sould also be noted that the 2002 Chung study found that the difference between males and females in the BSTc does not occur until after puberty, which poses some problems for a pre or early post natal hormonal causation theory.
Swaab thinks the BSTc is probably a part of a network in the brain involving the hypothalaumus and cortical areas.
"We only, by accident, hit on a little bit of it"
He also explicitly supported the idea that there is a biological causation for the whole range of gender identity variations:
"I think we talked about a scale like the Kinsey scale for sexual orientation – we should also have a gender identity scale. It is not either this or that; there is also something in between. The distribution will not be simple, but here will be people somewhere in the middle."
"So it is not the entire brain that is switching, it is some systems, and that may also be the explanation for the [gender identity] scale. Some systems do switch and others don’t and it depends on which systems have switched where you enter on the scale."
Other recent research (as reviewed by Zoe in earlier blogs) also supports the idea of certain sex differentiated brain areas being switched in ts or tg people while others are not.
So if that is the opinion of Swaab, perhaps the best qualified scientific researcher in the field, perhaps we can accept that tg is as likely to be biological as ts?