Nathalie Jonsson

Science Writer 

The Science of Sexual Preference

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As the 15th country in the world, the UK (or at least England and Wales) are closer than ever to allow and recognise same-sex-marriage (follow the status of the bill here).

It might be in relation to this that the Science Museum in London chose to dedicate this month’s ‘Lates’ session, held on the last Wednesday of each month, to exploring sexuality and sexual preference. Yesterday seemed jam packed with activities and lectures to discuss the role of a plastic surgeon in the a transgender person’s life, the sexual behaviour of bugs and to explain the Science of Sex.

By coincidence, Chinese researchers who have tackled that last topic in the lab released their results yesterday. They claim to have been able to change the sexual preference in mice and thereby discovered the chemical in the brain that makes some people prefer men and others prefer women. Their results showed that by completely removing the neurotransmitter serotonin (known to be involved in different behaviours like mood, appetite and sleep), male mice became willing to mount both male and female mice. When serotonin was injected into these male mice they reverted to mainly mounting females. Therefore, serotonin levels could be involved in sexual preference.

Since these results were released that conclusion has been heavily criticised. First of all, that serotonin is involved in sexual behaviour is not a new discovery. In fact, one of the side effects of certain antidepressants is a lower sex drive just because the levels of serotonin increase. And if high serotonin levels reduce the sex drive in people, it is not surprising to find that low levels of serotonin increase the sex drive in mice.
Secondly, the observation that the male mice with a high sex drive are less concerned with the gender of their partners does not necessarily say anything about their sexual preference. Perhaps, they just mount pretty much anything.

Lastly, as mention before serotonin is involved in many behavioural processes. At present, these observations do not provide enough of a basis to make any big claims about sexual preference. And in addition, since many people are taking antidepressants that do have an effect on sexual behaviour, I suspect that we would have noticed if ‘may change sexual preference’ was one of the additional side effects.

The whole thing reminds me of that ancient saying: “Beware of confusing ‘preference for sex’ with ‘preference for a particular gender’ and vice versa”

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