AILSA CHANG, HOST:
The next time you swat a fruit fly in your kitchen, take heart from the fact that people have probably been struggling with these unwanted dinner guests for around 10,000 years. That's because the common fruit fly may have first shacked up with cave dwellers. NPR's Nell Greenfieldboyce reports.
NELL GREENFIELDBOYCE, BYLINE: The common fruit fly, Drosophila melanogaster, may really bug you. Scientists love it as a tool for basic biology.
MARCUS STENSMYR: They are probably the most studied organisms on the planet. We have been working on them for over a hundred years. We know a lot of things.
GREENFIELDBOYCE: Marcus Stensmyr is a biologist at Lund University in Sweden who uses fruit flies to study the sense of smell. He says what's not been known is this. Where and how did this fly originally live out in nature?
STENSMYR: So you'll find them in your kitchen. You'll find them in my kitchen. And you'll find them in everyone's kitchen. But if you go out into the forest, you simply don't find them.
GREENFIELDBOYCE: Some genetic studies suggested that their ancestral home was south Central Africa. But expeditions didn't find the flies, so Stensmyr's team made a list of all the fruits that grow in this region and looked for any that matched up with what's known about fly preferences. They hit upon the marula, a yellow fruit the size of a plum with a hard pit in the middle. The team then went to a forest in Zimbabwe.
STENSMYR: We looked for the fruit. We found the fruit quickly. And once we found the fruit, we found tons of flies.
GREENFIELDBOYCE: Tons of them. And what's more, near those forests in Zimbabwe are caves, famous painted caves where the San tribes once lived.
STENSMYR: And these guys - they really, really loved the marula.
GREENFIELDBOYCE: Inside the caves, archaeologists have found millions of marula pits, the garbage of 10,000 years ago. Stensmyr says these people must have stored enormous amounts of the flies' favorite food.
STENSMYR: So the flies basically moved into the caves.
GREENFIELDBOYCE: And adapted more to living with people. Researchers tried putting the fruit in one of the caves, and the flies did indeed go for it. The study appears in the journal Current Biology.
DEBBIE ANDREW: I really loved it.
GREENFIELDBOYCE: Debbie Andrew is a developmental biologist at Johns Hopkins University who has studied fruit flies for decades.
ANDREW: They built a good story. I mean, it's very hard to prove.
GREENFIELDBOYCE: Still, she says that old saying time flies like an arrow, fruit flies like a banana needs to be changed to time flies like an arrow, fruit flies like a marula. Nell Greenfieldboyce, NPR News.
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