"They're Everywhere!": How Cockroaches Conquered Earth

Very few species can truly claim to live anywhere on earth. The brown-and-black German cockroach is one of them. But much has remained unknown about the species. Experts had not explained how they spread to all seven continents. And they had not figured out where the roaches began that journey either.

A new study, however, aims to shine a little light on that mystery to see what comes scurrying out. 

A team of researchers from across the globe studied the genes of over 280 Blattella germanica. The samples were gathered from 17 countries and 6 continents. They found that the roach’s DNA matched most closely to that of Blattella asahinai. That's the Asian cockroach. The first records of the critter are from Germany 250 years ago (hence its name). But now it seems far more likely that it first came from East Asia.  

“We confirm that B. germanica evolved from the Asian cockroach Blattella asahinai approximately 2,100 (years ago)," the team wrote in the study, published last week in the journal PNAS. They believe it first adapted to human settlements in India or Myanmar. 

Tracing the pathways of the German cockroach’s global takeover involved studying human history as much as the bug's genes. The wide-ranging pests most likely hitched rides with human traders. They would have found plenty of food and shelter in the cities where merchants stopped. In fact, German cockroaches don't live in the wild. Instead, they’ve evolved to live only in human-made structures.  

“It’s not just an insect story,” expert Stephen Richards told The Associated Press. “It’s an insect and humanity story.”     

Reflect: What do you think are some of the biggest ways humans impact other species?

GIF of cockroaches from GIPHY.