So a fruit fly goes to a bar ...

The news last week that scientists induced homosexual courtship in male fruit flies by changing levels of a neuro chemical was greeted with predictable headlines: "Scientists make fruit flies gay, then straight again." On science blogs, discussion raged about whether this meant that a drug altering sexual orientation would, or should, be developed by the demon Big Pharma. Others trotted out arguments about whether homosexuality was learned or genetic, and about its existence elsewhere in the animal kingdom, and then meandered into why places with large contingents of gays -- such as San Francisco and Boulder, Colo. -- are usually nice places to live.

As someone who studies animal behavior for a living, I've been at least as interested as anyone else in the emerging discoveries that many animals exhibit homosexual behavior. And, as it happens, I've become something of a go-to person on gay penguins (a subject for another day). But people seem to be missing the real reason the discovery is important, which has little or nothing to do with sexual orientation.

What David Featherstone and his colleagues at the University of Illinois at Chicago found is that male flies with a mutation -- a form of a gene called genderblind -- will court other males rather than females. What is exciting is that the researchers pinned down how and why.

They discovered that the gene controls transport of the neurotransmitter glutamate out of so-called glial cells, which are nervous system cells that do not conduct electrical signals but support other transmitter cells. Glutamate in turn can control the synapses, or junctions between other nerve cells, and synapse strength is important in determining many aspects of behavior. By experimenting with altering synapse strength chemically, independent of the mutation, the researchers homed in on exactly what was at work. Manipulating glutamate transmission, they discovered, allowed them to alter -- sometimes within hours -- whether the flies courted males or females. The altered males interpreted the odors of other flies (the primary come-hither signal) differently from their wild counterparts.

If what's sauce for the fly is sauce for the human, this could mean that chemicals in our own nervous systems are involved with sexual orientation too. And I'll admit that it's entertaining to imagine popping a pill to swing one way for a party, the other for a get-together at grandma's. But that dystopian possibility probably isn't in the cards. The truth is that chemicals no more control who we are sexually attracted to than they do anything else. Which is to say, they control everything and nothing.