Fruit Flies Put Evolution in Reverse

Jan. 12, 2009 -- If you could put an animal in a time machine and send it back to live in the distant past, would its DNA evolve in reverse, returning to the genetic code of its ancestors?

The intriguing idea has been tested by scientists in Portugal and the United States, using the fruit fly (Drosophila melanogaster) as the animal, and a laboratory to recreate the conditions of the past.

Modern-day fruit flies are the distant descendants of an original group that had been harvested in the wild back in 1975.

Over the following decades, 500 generations of flies grew up in different environments.

Different groups of insects were starved, exposed to greater humidity and so on in various experiments, and as a result developed specific characteristics, molded by these conditions.

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Henrique Teotonio and colleagues put these various populations back into the ancestral environment and let them reproduce for another 50 generations.

They then took a close look at a telltale stretch of DNA, on Chromosome 3, to see whether "reverse evolution" had taken place.

The answer: Yes, it had, but only up to a point.