Popular wisdom has it that we know all sorts of things about human pheromones, including knowing that they completely drive the behavior of adolescents, are thick in the air of certain bars, and are largely why Buffy thinks boys smell nice. But a pheromone is a chemical that specifically acts as a hormone in one person’s body but is produced in another’s. (Hence the name.) And, as Wade writes, there is no firm evidence that pheromones even exist in humans: “Hopes by the fragrance industry, among others, of finding human pheromones were dashed several years ago when it emerged that a tiny structure in the nose through which mice detect many pheromones, the vomeronasal organ, is largely inactive in humans, having lost its nervous connection with the brain.”
The authors, led by Ivanka Savic at Karolinska University Hospital in Stockholm (doesn't her name make her sound like a Swedish Vulcan? I'm picturing a blonde version of the character Kirstie Alley played in the second Star Trek movie) had previously identified two chemicals, abbreviated AND and EST, as potential human pheromones. The evidence was primarily a neuroimaging study which showed different patterns of activation in heterosexual men and women. Both chemicals activated areas known as the olfactory brain in both men and women. (In case you were wondering your olfactory brain consists of the amygdala, piriform cortex, anteriori insular cortex, orbitofronto cortex and anteriori cingulate cortex. And is it just me, or is the amygdala implicated in every single brain process?) But in men, EST also activated an area of the anterior hypothalamus, and in women AND activated a slightly different region of the anterior hypothalamus.
So the current study by Ivanka Savic (wasn’t Kirstie Alley cute in the second Star Trek movie? I don’t know why people give her shit about her weight, I think she wears it well.) took 36 subjects and divided them into heterosexual male, homosexual male and heterosexual female. The breeders were all Kinsey 0’s and the queers were all Kinsey 6’s (I didn’t think such people really existed) which must mean that they were classified by an interviewing process. The subjects were exposed to three kinds of odors (AND, EST and “ordinary odors” such as lavender and butanol) as well as odorless air for a baseline comparison.) The subjects were scanned using MRI and PET, their respiratory patterns were measured and they were interviewed about their emotional reactions to the smells.
Bottom line: the gay men had brains that let up like women’s when exposed to the testosterone derivative AND. In all other respects they resembled straight men.
I think this study is interesting, but it is also easy to make too much of it, which is in fact what Wade seems to do in his write up. First of all, this says nothing about nature and nurture in sexuality. It would only be evidence for the innateness of homosexuality if you could infer innateness from distinct neuroimaging patterns. But of course you can't. People who can read look different under brainscans when exposed to text than people who can't read. But reading is not innate.
Wade outlines two possible causal relations here
The different pattern of activity that Dr. Savic sees in the brains of gay men could be either a cause of their sexual orientation or an effect of it. If sexual orientation has a genetic cause, or is influenced by hormones in the womb or at puberty, then the neurons in the hypothalamus could wire themselves up in a way that permanently shapes which sex a person is attracted to.
Alternatively, Dr. Savic's finding could be just a consequence of straight and gay men's using their brain in different ways.
Wade gives us two hypotheses: (1) homosexuality has a biological cause, either in genes or hormone exposure, and this brain pattern is a link in the causal chain between root cause and behavior and (2) homosexual behavior, however it is caused, leads brains to be organized in the way we see.
Wade simplifies too much, though. Both of his causal stories involve causation going in only one direction and coming from a single source. Also, causation here freely jumps between biological entities like hormones, to social entities like behavioral categories. More work needs to be done.
Finally, I’m distressed that Wade continues to cite the work of Simon LeVay:, who asserted that they hypothalamuses of gay and straight men were different on the basis of the examination of 41 corpses, where sexual identity was inferred from cause of death. (They gay men were the ones who had died of AIDS.) I don’t know why this study keeps cropping up. It really blew.
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