US and Canadian researchers have evolved a population of fruitflies that can count. The result, presented on 9 July at the First Joint Congress on Evolutionary Biology in Ottawa, Canada, supports the notion that the neural mechanisms underlying basic arithmetic skills first emerged hundreds of millions of years ago. It could also eventually offer a key to understanding why some people have problems with numbers…
During a 20-minute training period, flies were exposed to either two, three or four flashes of light — two and four flashes coincided with a vigorous shake administered by placing a electric toothbrush next to the box containing the flies. After a brief rest, the flies were returned to box and shown the light flashes. Despite a dislike for being shaken, most of the flies were not able to learn to associate the negative stimulus with the number of flashes. But 40 generations later, they could.
The researchers caution that the work is preliminary and that they do yet know what genetic changes are behind the insects’ evolved number sense.
What I find interesting is exactly how this constitutes selection pressure. The flies certainly don’t like being shaken, but that’s entirely irrelevant if there isn’t some sort of reproductive advantage to be had from recognizing when the shaking will occur. Clearly there is, and we could speculate all day long as to why flies that associate the flashes with negative stimulus pass on more of their genes than the other flies, but I would like to see some experimental data showing the details. Does shaking disorient the flies? Does it interrupt the mating process? Does it affect fertility? Perhaps the paper that comes from all this can shed some light.
Now excuse me while I go murder the fruit flies that appear to have evolved to make my kitchen just awful for the past week.