A new study finds that both drugs and genetic manipulation can turn the homosexual behavior of fruit flies on and off within a matter of hours.

While the genetic finding supports the thinking that homosexuality is hard-wired, the drug finding surprisingly suggests it's not that simple.

In fact, homosexuality in the fruit flies seems to be regulated by how they interpret the scent of another.

Homosexuality is widespread in the animal world. But scientists have long debated whether, in humans a "gay gene" exists.

Previous research in humans has suggested that how we interpret scents given off by another person might impact our sexuality.

In the new work, University of Illinois at Chicago researcher David Featherstone and coworkers discovered a gene in fruit flies they call "genderblind," or GB. A mutation in GB turns flies bisexual.

GB transports the neurotransmitter glutamate to brain cells. Altering levels of glutamate change the strength of nerve cell junctions, called synapses, which play a key role in human and animal behavior.

Post-doctoral researcher Yael Grosjean found that all male fruit flies with a mutation in their GB gene courted other males.

"It was very dramatic," Featherstone said. "The GB mutant males treated other males exactly the same way normal male flies would treat a female. They even attempted copulation."

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I'm totally downloading the paper from Neuroscience right now.