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The world’s most common cockroach is ‘a monster of our own creation,’ study finds

A new study into the evolutionary history of the most prevalent cockroach shows that it's "a monster of our own creation."

The German cockroach evolved alongside humans, and its only natural habitat is inside our buildings

Closeup of a brown cockroach perched on a rock

Despite its name, the German cockroach isn't from Germany. In fact, it's not really from anywhere.

Blattella germanica, the most prevalent species of cockroach on the planet, was named for specimens collected in Germany in the 1700s. But it's not native to any one country. Its only true home is inside our homes — and our workplaces, and our schools, etc.

In fact, according to a new study, its entire evolution is tied to human history.

"It's the most widespread, yuckiest pest we can think of inside — but it's a monster of our own creation," Edward Vargo, an urban entomologist at Texas A&M University, told As It Happens host Nil Köksal.

"It's basically everywhere in the world that has buildings, but there are no natural populations of this species that we can find in nature. So it's been a mystery as to where did these come from."

Vargo and his colleagues set out to solve that mystery. Their new study, published in the Proceedings of the National Academy of Sciences, details the surprisingly rapid and successful evolutionary history of the world's most common roach.

Our constant companion for millennia

By analyzing the genes of over 280 cockroaches from 17 countries and six continents, the researchers determined the German cockroach branched off from its closest wild relative — the Asian cockroach — about 2,100 years ago.

That makes it "a relatively new species in biological time," Vargo said.

"It became adapted to human built-environments and then completely lived inside of those buildings and then spread around through military conquests and commercial activity throughout the world."

It likely spread out from southeast Asia alongside humans, the study notes, hitching rides with travelling armies, merchants and trade ships.

Smiling man with white hair and glasses

Essentially, everywhere humans have gone, the mighty cockroach has followed. And despite our best efforts, it's only getting mightier.

"They've spread very rapidly, and they developed resistance very quickly against almost all insecticides that are used against them," Vargo said.

Understanding their genes can help us fight them

Michael E. Scharf, a retired urban entomologist from the University of Florida, welcomed the research that sheds light on what he calls "one of the most important, and long-standing, invasive pests that we have."

"As the urban entomology field seeks to understand how fast insecticide resistance builds in German cockroach populations and spreads to new locations, this new knowledge provides insights into the adaptability of the roach genome that enables such rapid changes at a population level," he told CBC in an email.

Scharf, who is not involved in the research, says the next step would be "finding hotspots in the genome that give rise to mutations that cause insecticide resistance."

A cockroach specimen, labelled "Blattella germanica," pinned to a square piece of foam

In other words, understanding the roach's genes could help us keep them at bay.

That's Vargo's hope as well. Cockroaches, he says, are a huge public health concern. They contaminate food, they spread disease and they're a major trigger for asthma and allergies.

"The better we're able to control the populations and eliminate populations, especially from high-density housing [and] low-income housing areas, you know, the better wewill be able to suppress their public health effects," he said.

Vargo says the findings also show that humans aren't as separated from the natural world as we like to think.

"We're seeing urbanization occur at a rapid rate all around the world. There's enough indoor environment to be a major biome or ecological system," Vargo said.

"We don't know what's down the road as far as what species will be able to survive, and actually thrive, in these kinds of environments. So that's something I think we need to think about."

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