Research suggests that homosexuality may not be solely genetically programmed

“Our study offers a conceptual basis to explain how nature and nurture interact in shaping human sexual orientation,” said one of the researchers Daisuke Yamamoto, professor at Tohoku University in Sendai, Japan.

The scientists discovered that homosexual behaviour in certain groups of male fruit flies can be altered by their environment. Specifically, they showed that the sexual preferences of male fruit flies with a mutant version of a gene known to affect male sexual behaviour can vary depending on whether the flies are reared in groups or alone.

The neurons that express the fruitless (fru) gene “basically govern the whole aspect of male sexual behaviour,” Yamamoto explained.

Normal male fruit flies tap the abdomen of a female to get a whiff of her sex pheromones before pursuing her to mate. In contrast, males with a mutant version of the fru gene show no interest in females. Instead, they set off in vigorous pursuit of other males.

Yamamoto wanted to analyse the role of vision in the courtship behaviour of normal and mutant fruit flies. The researchers found that visually induced courtship behaviour in the fru mutant males can be blocked by isolating them right after their emergence from the pupa.

The finding that courtship behaviour in mutant flies can change according to how they are reared suggests that experience can shape behaviour. Yamamoto said he was “terribly surprised” by the results, because he had previously never doubted that male-to-male courtship in fru mutant males was “solely genetically programmed”.

The findings appeared in the journal Nature Communications.