The Null Device

Ambisexual mice

Scientists in China have found that mice bred to not be receptive to serotonin have no sexual preferences for either sex:
When presented with a choice of partners, they showed no overall preference for either males or females. When just a male was introduced into the cage, the modified males were far more likely to mount the male and emit a "mating call" normally given off when encountering females than unmodified males were.
However, a preference for females could be "restored" by injecting serotonin into the brain.
The researchers have cautioned against drawing conclusions about human sexuality from the result.

The lazy takeaway from this, as seen in news sites, is that serotonin affects sexual orientation, with the suggestion that low serotonin might be the secret to the inexplicable condition known as homosexuality. I'm wondering whether a more plausible conclusion is that, with sexual selection being about competition amongst fit individuals, a prerequisite for having an active sexual preference is passing an internal test of subjective fitness, i.e., being aware that one has sufficiently high status to be picky. In other words, mice without functioning serotonin receptors perceive themselves as losers who will take anything that's warm and regard it, being more than they're entitled to, as a win.

There are 4 comments on "Ambisexual mice":

Posted by: Thu Mar 24 15:27:08 2011

Has anyone done studies on gay or bisexual human men and their levels of serotonin and their receptiveness to it?

Posted by: Thu Mar 24 15:29:49 2011

By the way, your CAPTCHA program is way, way too aggressive. I've tried to post a few times, typed the text, and been told it doesn't match, when there's simply no ambiguity about the text at all.

Posted by: Greg Fri Mar 25 09:14:58 2011

Aren't those two alternatives the same thing said differently?

I haven't followed the story up yet, so this has probably been said 1000 times on the Nature and Guardian reader forums, but the mice didn't seem to become homosexual - rather they didn't exhibit a preference for gender. Homosexuals certainly prefer one gender over the other.

I have seen interesting evolutionarily-grounded hypotheses about homosexuality which don't imply a lack of status; if anything, the opposite. For example, one I read proposes that if one has sufficiently many successfully-reproductive siblings, one will do better to become a non-reproductive priest/artist/equivalent-for-appropriate-historical-era, to bring *high* status to the family as a whole, than to merely add a couple more offspring of one's own.

I don't have a reference and am not biologist enough to have an opinion for or against the above, but I think it's good that a scientific view doesn't have to be insulting.

Posted by: acb Fri Mar 25 12:18:09 2011

It's a difference of phrasing. The BBC story seemed to suggest that low serotonin can add variety to an individual's sexual preferences; what I'm suggesting is that it doesn't add to them but knocks them out, i.e., that sexual preferences are a luxury for those who have self-perceived status above a specific cutoff point.

And this doesn't look like classic/standard homosexuality. It could perhaps be analogous to situational homosexuality in environments such as prisons or armed forces.