Once upon a time, between 2 million and 4 million years ago, the fruit fly lineage split. One sister species, known today as Drosophila simulans, kept up the parent’s habit of hanging around and consuming ripe fruit. The other, the D. melanogaster beloved by modern geneticists, took a different path. It evolved a more active alcohol dehydrogenase (ADH) enzyme, making it better suited to slurp the high-ethanol content of perfectly rotten fruit.
It’s a nice story, one that evolutionary biologists touted for decades as an illustrative example of molecular adaptation. Too bad it’s wrong.
Last year, researchers at the University of Chicago refuted that just-so scenario by resurrecting the ancient ADH enzyme from the last common ancestor of D. simulans and D. melanogaster. They replaced a modern D. melanogaster’s ADH with the prehistoric version of the protein, from before flies colonized rotten fruit, and it made no difference to D. ...
