How cockroaches came to rule the worldA team of scientists has found that, without humans, the most pervasive species of cockroach probably wouldn’t exist.
https://www.washingtonpost.com/climate-environment/2024/05/20/cockroach-spread-habitat-humans/
The world’s most widespread type of cockroach — a tiny, tan pest called the German cockroach — is at this moment crawling through countless buildings, hiding in the dark nooks of hotel rooms, restaurant kitchens and, if you’re unlucky, your own home — anywhere it can squeeze its little body and scavenge for the crumbs we drop.
Yet at the same time, when scientists search for its natural habitat, they can’t find it. It’s not native to any wilderness in Germany. In fact, it doesn’t seem to have any home in the wild anywhere in the world.
“Its origin has been a mystery,” said Edward Vargo, an urban entomologist at Texas A&M University. “These only exist in buildings.”
Now scientists who conducted a DNA analysis of the cockroach say they have solved that 250-year-old puzzle of where this ubiquitous bug is from.
The answer is us. We made the cockroach. The species branched off from its closest cousin only about 2,100 years ago — a blink in evolutionary time — and is adapted entirely to living in dwellings alongside humans.
“It formed as a species due to its adaptation to human-made environments,” said Vargo, who co-wrote a study on the cockroach’s genesis published Monday in the Proceedings of the National Academy of Sciences. “It’s a creation of human-made environments.”
The cockroach is a testament to the adaptability of nature, even to the most unnatural environments and in the face of hostile human roommates who try — often unsuccessfully — to trap, poison or crush the bugs to death. That adaptability has allowed the insect to crawl its way from Alaska to Antarctica and become one of the world’s most destructive pests.
The German cockroach has made its way around the world by hiding in cargo on planes, trains and automobiles. The first records of the pest popped up in Europe in the mid-18th century shortly after the Seven Years’ War, which probably allowed the insect to spread around the continent by hitchhiking with soldiers.
Europeans named the new bug after their enemies in that conflict. Russians called it the “Prussian cockroach,” naming it after the old German state, while some of Russia’s enemies called it the “Russian cockroach.”
The Swedish biologist Carl Linnaeus called it the German cockroach, and that name stuck. (Sweden fought Prussia in the war.)
“The name is truly biased, and shows a personal or national or political preference at that time,” said Qian Tang, a research associate at Harvard who led the study.
For centuries, the insect’s real birthplace remained a mystery even as it conquered the world. It reproduces more quickly than other cockroach species, supercharging its ability to evolve. One of the keys to its success is its resistance to most poisons thrown at it.
“If we can know the origin of the species,” Tang said, “we can try to identify the mechanism of this rapid evolution of insecticide resistance.”
To pinpoint the insect’s inception, Tang and his team collected nearly 300 individual cockroaches from 17 countries on six continents to map its global spread.
Analyzing the cockroaches’ genomes, Tang and his colleagues concluded the species branched off from a different species called the Asian cockroach — also an invasive species in the United States, though its primary habitat is outdoors — after moving in with people in either India or Myanmar more than two millennia ago. From there, German cockroaches hitched a ride with travelers during the Islamic dynasties and European colonialism.
Today, the health and economic cost of that spread is huge. And it goes beyond lost business at hotels and restaurants when guests see them scurrying. Cockroach infestations can trigger asthma for those allergic to their saliva and feces.
“It’s a big public health concern, especially in low-income housing where the treatments for German cockroaches leave a lot to be desired,” Vargo said.
The study was born out of Tang’s doctoral work at the National University of Singapore. Growing up in China, Tang loved to watch nature documentaries about wild animals and read books about dinosaurs. As a kid, he never suspected his interest in evolutionary biology would lead him to studying a household pest.
“I wasn’t thinking of that,” he said.
Now the researchers want to find the genes that have allowed German cockroaches to thrive in the urban jungle to better manage it and other pests.
“With the increasing urbanization of the world, this is just going to be a more common phenomenon,” Vargo said. “The urban environment is becoming a much more prevalent sort of ecosystem.”
As for that name? Tang thinks its time to drop the German moniker.
“It’s probably necessary to rename it in a more scientific fashion.”
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