Fruit flies may seem pretty innocuous, to us. But in their own little world, male fruit flies are aggressive fighters, who will headbutt and shove each other…even box. There is one thing that'll calm them down though: the female touch.

Researchers raised males with varying amounts of contact with the fruit fly fairer sex. And they found that males who'd spent an entire day hanging out with ladies—including a chance to copulate—were more peaceable than those who had lacked such contact.

The researchers thought the sex act might be the secret. But the sex alone won't do the trick. The key to peace was prolonged physical contact with females—which causes female pheromones to rub off on the males. Those chemical compounds activate about 20 neurons in the male brain, which tamp down the brain's aggression circuit, and bingo: no more fighting. The results appear in the journal Nature Neuroscience. [Quan Yuan et al., Female contact modulates male aggression via a sexually dimorphic GABAergic circuit in Drosophila]

As for human aggression, this study doesn't say much. But we do share genes with flies, and our neural circuitry has similarities. So the researchers say work on hot-headed flies could someday clue us in to why humans fly into a rage.

—Christopher Intagliata

[The above text is a transcript of this podcast.]

[Scientific American is part of Nature Publishing Group.]