Scientists at the University of Utah have obtained 'lesbian' nematode worms by flipping a genetic switch in the hermaphrodite worms' 'brain'. Nematode worms (Caenorhabditis elegans) are either male or hermaphrodite (having both male and female sexual organs). These hermaphrodite worms are commonly referred to as females, as they are basically females that can fertilize themselves, but prefer mating with males instead because they get many times more eggs and a more diverse gene pool.

The female worms are attracted by the males' scent. When scientists flipped a gene in their nervous system to be the same way as in a male worm, the females began chasing other females for mating, mimicking the sexual behavior of males. Also, other male behavioral characteristics were noticed, even if the gender remained female.

"They look like girls, but act and think like boys," Utah researcher Jamie White, who worked on the study published in the journal Current Biology, said in a statement. The gene normally influences gender, but the researchers only manipulated it in the brain.

The study, funded by the National Science Foundation, was led by Erik Jorgensen, scientific director of the Brain Institute at the University of Utah. The research is detailed online today in the journal Current Biology.

Most scientists think a wide range of factors such as genetics, hormones and environment may play a role in determining sexual orientation in humans, but there is no real answer yet. Jorgensen himself warned that findings in worms may or may not apply to humans, even if it advances understanding of homosexuality.

"For the most part they are females," Jorgensen said. "It's really hard to tell that they are hermaphrodites, but they do make these few sperm."

The most important advancement in understanding sexual orientation is that sexual attraction is wired into brain circuits common to both sexes of worms, and does not appear to be, as previously suggested, related to gender-specific pathways.

"We cannot say what this means for 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."

Caenorhabditis elegans specimens survived the Space Shuttle Columbia disaster in February 2003.