Pheromones and Homosexuality

A new study suggests that humans respond to pheromones. Not only that, but the response differs based on sexual orientation. A news summary of the study says:

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The scientists exposed heterosexual men and women and homosexual men to chemicals found in male and female sex hormones. One chemical is a testosterone derivative produced in men's sweat. The other chemical is an estrogen-like compound in women's urine.

These chemicals have long been suspected of being pheromones, molecules emitted by one individual that evoke some behavior in another of the same species. Pheromones trigger basic responses, such as sexual attraction, in many animals.

But scientists have long debated if humans respond to pheromones. The new study suggests that pheromones indeed play a part in making humans sexually attractive to one another.

In a previous study a few years ago, the Swedish researchers showed that the brain's hypothalamus region, which is involved in sexual behavior, becomes activated when men smell EST (the estrogen derivative) and women smell AND (the testosterone compound), but not vice versa.

For their new study, the scientists added a sexual-orientation element, which revealed a difference in the brain activity of gay and straight men.

The researchers found that the testosterone compound activated the hypothalamus in homosexual men and heterosexual women, but not heterosexual men. Conversely, the estrogen compound activated the hypothalamus only in heterosexual men.

I'm not a neuroscientist so I cannot analyze the paper, but I took a quick look at the conclusion section of the paper. The authors list several issues that need to be considered. First is the issue of whether the response is a result of hardwiring in the brain, sensitization, or association. Second is how the pheromone is detected; the authors think that the timing suggests detection in the nose. Third whether the concentration of the pheromones in the experiment are physiologically relevant.

The issue of why homosexuality exists is a contentious one. My own [non-scientific] opinion is that the answers are complex and cannot be easily catagorized. I'm comfortable with some having a strong biological basis for their orientation, others having a social or psychological motivation, and others being somewhere in between. Biology is resistant to pigeon-holes.