How Did Cockroaches Reach Global Domination?

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Earth is home to approximately 4,600 cockroach species, but none is as widespread as the German cockroach (Blattella germanica), found wherever humans live. Despite its name, the German cockroach arrived in Germany only a few decades before receiving its moniker from Swedish biologist Carl Linnaeus, who named it during the Seven Years’ War against what is now Germany. Its journey to Europe and the Americas has been a recent leg in its global spread.

Research published on May 20 in the journal Proceedings of the National Academy of Sciences USA traces the origins and worldwide spread of this common pest. The researchers attribute its geographical success to its remarkable ability to adapt to human environments.

“I’ve been looking forward to someone doing something like this,” says Dominic Evangelista, an evolutionary biologist at the University of Illinois Urbana-Champaign, who was not involved in the study. “We’re well aware of how humans affect the natural world, but we’re less aware of how organisms in nature might be adapting to us.”

German cockroaches have swiftly and specifically adapted to living with humans, says Qian Tang, an evolutionary biologist at Harvard University and co-author of the study. To understand these adaptations—and how to potentially control the cockroach—researchers need to trace its origins.

Tang and his team gathered samples from cockroach researchers worldwide, often sourced from local pest control companies. They analyzed 281 German cockroaches from 17 countries, along with specimens from related species, examining their genomes to map the global population’s relationships.

The analysis revealed that the German cockroach is closely related to an Asian species, Blattella asahinai, with the two likely diverging around 2,100 years ago. Tang likens their relationship to that of wolves and dogs, highlighting their physical similarities.

From their Asian origins, German cockroaches spread in two major waves. The first wave, about 1,200 years ago, likely involved traders and soldiers of the Islamic empires. The second wave, around 390 years ago, coincided with advancements in home-heating technology and steam-powered ships, facilitating their spread into Europe and the Americas. The researchers estimate that German cockroaches first arrived in Europe about 270 years ago, aligning with the earliest records of their presence.

German cockroaches developed two key adaptations for thriving alongside humans: rapid evolution of insecticide resistance (resistant to about 40 active ingredients) and a social foraging strategy similar to ants. However, the origins of these skills remain unclear. Tang suggests that understanding the cockroach’s history could shed light on these adaptations and potential countermeasures.

Evangelista appreciates the study’s focus on the German cockroach’s history but advocates for more research on other cockroach species, particularly less notorious ones.

“I would love to see a similar study with the American cockroach (Periplaneta americana, another common pest) and studies of cockroaches that are not hated by anyone,” Evangelista says. “If we had better studies of some more charismatic cockroaches, that might broaden people’s perspective on how interesting biodiversity is in general.”