Researchers study how the German cockroach spread globally

A MARTÍNEZ, HOST:

The German cockroach is the most widespread cockroach species in the world. But despite its name, it can be found on every continent except Antarctica.

QIAN TANG: Yet nobody knows where they come from.

MICHEL MARTIN, HOST:

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That is Qian Tang. He led a study on the origins of the German cockroach and how it spread globally. The study was recently published in the scientific journal the Proceedings of the National Academy of Sciences, which I guess is why we're talking about this with our morning coffee.

MARTÍNEZ: (Laughter) I'm glad we cleared that up. Now, researchers found that the German cockroach likely evolved from the Asian cockroach.

TANG: The Asian cockroach, it's natural habitat is believed to be in south Asia.

MARTIN: It was there the two species are believed to have diverged around 2,000 years ago.

TANG: That's probably the time point that their ancestors are fully adapted to the human household conditions.

MARTÍNEZ: The German cockroach fed on crops and plants made by humans, food they often found inside people's homes. Now, over time, they adapted to indoor life.

TANG: They are less cold tolerant, and they cannot really survive outdoor. But this becomes like an advantage in the modern household, when the heating over winter is constant.

MARTIN: Improved household conditions like indoor heating and better insulation meant that German cockroaches could now survive colder climates.

MARTÍNEZ: Like in Europe, which is where German cockroaches spread in the mid-1700s.

MARTIN: German cockroaches can't fly - thank goodness...

MARTÍNEZ: (Laughter).

MARTIN: ...So they hitchhiked on people. Oh, my gosh.

TANG: The German cockroach started to expand from Europe to the rest of the world.

MARTÍNEZ: Tang says tracing the origins of the German cockroach helps us understand their gene pool and why they are so resistant to 40 ingredients commonly used in insecticide.

TANG: That may help us in the future to develop effective management methods on these species, so maybe to develop some different chemicals that they will not resist so much.

MARTIN: So while humans are the reason the German cockroach is everywhere, there are still scientific mysteries to solve before we can control them?

MARTÍNEZ: I guess...

MARTIN: What?

MARTÍNEZ: ...If you can't beat them, join them?

MARTIN: No.

MARTÍNEZ: Squish them?

MARTIN: No.

MARTÍNEZ: Brush them off?

MARTIN: No.

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MICHEL MARTIN AND A MARTÍNEZ: This is NPR News. Transcript provided by NPR, Copyright NPR.