Flies Evolve to Count

Researchers breed fruit flies that, after 40 generations of conditioning, have acquired the ability to react to numbers.

Jul 12, 2012
Hayley Dunning

A team of geneticists have produced the first example of skills gained through directed evolution, by teaching fruit flies to react to a certain number of light flashes. In 20-minute sessions, flies in a container were exposed to flashes of light, with two or four flashes preceding a shake of the container. The experiment was designed to bring out what was assumed to be an innate ability to count in animals. Originally, none of the flies could anticipate the shake, but the 40th generation of shaken flies seemed to have acquired the skill to discern the correct number of flashes associated with a shake during the exercise, and prepare accordingly.

The research team, which presented its findings this week (July 6–10) at the First Joint Congress on Evolutionary Biology in Canada, says the flies can now be used to understand how we process numbers. They suspect numerical skills are rooted deeply in the animal lineage, as many animals have shown some basic capabilities, but delving into the genetic make-up of the wild type and evolved flies could pinpoint the basis for such skills. It could also reveal the genetics of disorders like dyscalculia, which affects people's ability to do basic arithmetic.

“This project was really about getting people interested in using fruit flies as a model system for understanding numerical competence and its evolution,” said study co-author Tristan Long of Wilfrid Laurier University in Waterloo, Canada told Nature. “The obvious next step is to see how [the flies’] neuro-architecture has changed.”