Is the Brain Unisex?
Gender is hugely complex, and humans have long realised that it’s not necessarily binary and it doesn’t necessarily match up to biological sex. Research is now beginning to catch up with these ideas. In one study, researchers Gero Miesenböeck from the Oxford University and J. Dylan Clyne from Yale University looked into the neurological differences between male and female fruit flies. To attract a mate, male fruit flies ‘sing’ by sticking out one wing and vibrating it, but the 2,000 neurons responsible for this behaviour are actually present in females too—so Miesenböeck and Clyne wondered why their behaviours differed. They genetically modified the flies so a beam of light could activate the courtship neurons, then placed a female in a ‘miniature sound studio’ that could pick up any tiny noise. A pulse of light was targeted at the neurons responsible for singing, and this artificial trigger caused the female fly to stick out her wing and sing. Professor Miesenböeck comments, “When we analysed the songs, we found there were subtle differences—the pitch was a bit off, the rhythm was off, the song, overall, was less well controlled.” This is probably due to subtly different wiring, but the fact she played at all is fascinating. It suggests that the wiring for both sexes is very similar, so what determines behaviour is not the existence of a certain group of neurons, but whether those neurons are switched on. There must be some kind of “master switch” that sets the gender of the fly, or perhaps more individual switches for different groups of behaviour. The next goal is to find these switches. The brains of flies are a far cry from our own, but it’s intriguing anyway—it could help explain a lot about the gap many of us experience between gender and sex.