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How cockroaches spread across the world and became the plague we know today

DALLAS (AP) — They’re six-legged, furry invaders that just won’t die no matter how hard you try.

Cockroaches are experts at surviving indoors, hiding in kitchen pipes or musty drawers. But they didn’t start that way.

A new study uses genetics to map the spread of cockroaches around the world, from humble beginnings in Southeast Asia to Europe and beyond. The findings span thousands of years of cockroach history and suggest the pests may have spread around the world by hitching a ride on another species: humans.

“It’s not just an insect story,” says Stephen Richards, an assistant professor at Baylor College of Medicine, who studies insect genes and was not involved in the study. “It’s a story about insects and humanity.”

Researchers analyzed the genes of more than 280 cockroaches from 17 countries and six continents. They confirmed that the German cockroach – a species found worldwide – actually originated in Southeast Asia and likely evolved from the Asian cockroach about 2,100 years ago. Scientists have long suspected that the German cockroach is of Asian origin, as similar species still exist.

The research was published Monday in the journal Proceedings of the National Academy of Sciences.

The cockroaches then traveled around the world via two main routes. They traveled west to the Middle East about 1,200 years ago, perhaps hitchhiking in soldiers’ bread baskets. And according to the reconstruction of scientists and historical data, they could have hidden on the trade routes of the Dutch and British East India Companies to reach Europe about 270 years ago.

Once they arrived, inventions such as the steam engine and the indoor sewage system likely helped the insects travel further and find a cozy home indoors, where they are most commonly found today.

Researchers say studying how cockroaches conquered past environments could lead to better pest control.

Modern cockroaches are difficult to keep at bay because they quickly evolve to resist pesticides, said study author Qian Tang, a postdoctoral researcher who studies insects at Harvard University.

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