THURSDAY, Oct. 25, 2007 (HealthDay News) -- Sexual attraction is hard-wired into the brains of small worms called nematodes, say scientists who genetically manipulated some of the creatures to make them attracted to the same sex.
The finding might give some insight into sexual attraction generally, the researchers said.
"Our conclusions are narrow in that they are about worms and how attraction behaviors are derived from the same brain circuit. But an evolutionary biologist will consider this to be a potentially common mechanism for sexual attraction," biology professor Erik Jorgensen, scientific director of the Brain Institute at the University of Utah, said in a prepared statement.
"The conclusion is that sexual attraction is wired into brain circuits common to both sexes of worms and is not caused solely by extra nerve cells added to the male or female brain," he said. "The reason males and females behave differently is that the same nerve cells have been rewired to alter sexual preference."
Nematodes, which live in the soil and eat bacteria, have the same genes as many other animals and are often used as models for human research.
It's difficult to say what these findings in nematodes mean in terms of human sexual orientation, but "it raises the possibility that sexual preference is wired in the brain," Jorgensen said. "Humans are subject to evolutionary forces just like worms. It seems possible that if sexual orientation is genetically wired in worms, it would be in people, too. Humans have free will, so the picture is more complicated in people."
The study was published online Thursday in the journal Current Biology and was expected to be published in the Nov. 6 print issue.
The Nemours Foundation has more about sexual attraction/orientation.