Sexuality Gene?

"In the female, what we see is when we turn on this gene there, just like when it's turned on in its normal position in a male, that these females now behave like males. That is, they carry out the male courtship," Baker says. Their results show that a single gene can determine how females and males detect and respond differently to sexual cues.

So, is this new evidence that sexual orientation may be built-in to people? Baker points out that this was an experiment in flies, not humans. "Whereas I am one who believes that there's probably a genetic basis to complex behaviors in people, it's not nearly as rigid a basis as you see in a fruit fly, it's much more influenced by who we are individually, what our upbringing was and so forth," says Baker.

He says the finding is important because it's the first time a "master switch" has been proven to control a complex behavior. "We haven't known about this for any other behavior, and so it's been up in the air, how do behaviors get built into the nervous system," says Baker. "Was it by single dedicated genes like this building particularly important behaviors, or is it somehow all the genes working together and the behavior arising as some emergent property out of the complexity of our nervous systems?" In the same way certain master genes shape physical traits, like the number and location of limbs, Baker says, "This says we may be able to think about behaviors in the same way. They may have a dedicated set of genes for important behaviors that build them just as the physical parts of our body are built."

Even though people share many genes with fruit flies, the fruit fly master gene can't explain differences between men and womens' behaviors. "I wouldn't be surprised if this gene was there in people, and had a similar role, but we don't yet know," says Baker.