How one of the world’s most successful indoor pests took over the planet

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The cockroach that came out of the sink drain and ran under the refrigerator? The nocturnal creature was likely a German cockroach, and its ancestors bothered people more than 2,000 years ago in South Asia, a new study finds.

The research, published on May 20 in the journal Proceedings of the National Academy of Sciencesshowed that insects’ journey, from cleaning in ancient Asian civilizations to snuggling under the kitchen floor, is closely aligned with major historical shifts in global trade, colonization and warfare.

German cockroaches, scientifically known as Blattella germanica, are ubiquitous in cities across the United States and around the world. The resistant pests first appeared in scientific records 250 years ago in Europe, hence the German nickname, but little is known about their origin.

To find out how the cockroaches got there and spread to other parts of the world, study first author Dr. Qian Tang and his collaborators asked scientists and pest control experts from around the world for local specimens. The research team received 281 samples of German cockroaches from 57 locations in 17 countries and studied their DNA to trace their evolution.

“Our main goal was to show how a species can travel with humans and how genetics can make up for the missing part of the historical record,” said Tang, an evolutionary biologist who is now a postdoctoral research associate at Harvard University.

Using genomic data from the samples, Tang was surprised to learn that the lineage of the modern cockroach goes back much further than 18th-century Europe. The insect evolved from the wild Asian cockroach, scientifically known as Blattella asahinai, 2,100 years ago, according to his research.

Cockroaches and trade routes

Around this time, Tang and his colleagues speculate, people in what is now India or Myanmar began planting crops in the Asian cockroach’s natural habitat. The insects adapted – changing their diets to include human food – and then transferred their territory to human homes.

A millennium later, as trade and military activity grew between South Asia and the Middle East and, later, Europe, domesticated cockroaches spread westward, probably hitching a ride in people’s lunch baskets. soldiers and travelers. The study team’s genetic analysis places the first entry of insects into Europe around 270 years ago. This estimate approximates the date when famous Swedish naturalist Carl Linnaeus first described them in 1776, about a decade after the Seven Years’ War devastated Asia, Europe and North America. Cockroaches arrived from Europe to the Americas about 120 years ago, the study found.

“Insects are part of the fabric of human culture,” said Dr. Jessica Ware, curator of invertebrate zoology at the American Museum of Natural History in New York City, who was not involved in the research. “We have known for a long time that people are moving many pest species. And we know that transatlantic trade routes were likely to blame for the spread of German cockroaches. But seeing that actually reflected in the genetic signature of these populations was very exciting.”

Humans have been doing this at home ever since, she said. “The things that have allowed humans to thrive — indoor plumbing, indoor heating — are things that have also allowed cockroaches to thrive,” Ware said. “By creating sewers beneath our cities, we couldn’t have provided a better buffet.”

Next, Tang plans to sequence the complete genomes of his hundreds of specimens to learn how German cockroaches adapted so successfully to the human environment. “For example, the German cockroach has insecticide resistance that is not detected in many other pests,” he said. “How can they evolve so quickly? Is it something that is already in your genes, but was revealed because of anthropogenic pressures?”

Insects also demonstrate social behaviors, communicating with each other about where to find food. Tang wants to find out whether this ability is also a survival trait that cockroaches have humans to thank for.

Correction: An earlier version of this story misstated Carl Linnaeus’s area of ​​expertise.

Amanda Schupak is a science and health journalist in New York City.

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