The roach approach: How the bugs got everywhere

We at Wknd weren’t sure if we should venture here, but the story is so riveting, we had to try.

It’s a tale that begins, well, a long, long time ago. Cockroaches have been around for at least 100 million years — about 98 million more than humans.

So the next time you’re tempted to think: “Ugh, how did you get here?”, it might be worth considering that the cockroach could really be thinking that too.

Besides which, the answer to how it got everywhere… is also us.
It turns out, the German cockroach — now the most widely found variant on the planet — would never have scuttled so far (oh, the horror), if not for humans.
A study of 281 cockroaches from 17 countries across six continents, published in the journal Proceedings of the National Academy of Sciences this year, found that this species, Blattella germanica, evolved about 2,000 years ago from the Asian cockroach (Blattella asahinai), found in the Bay of Bengal regions of India and Myanmar.
It travelled from there, presumably in the boots, bags and crumb-filled pockets of armies and merchants, ending up further and further from home, as trade routes unfurled, and then further again, as European colonisers turned up with pockets of their own.
The species was first classified by Swedish biologist Carl Linnaeus in 1776, and got its misleading name because Linnaeus collected his specimens in Germany, and believed they had spread from there around the world.
The German cockroach did turn out to be the most dominant strain in Europe, but later studies would show, rather confoundingly, that it seemed to have no close relatives there. Its genetic markers didn’t match those of most cockroach species native to Europe.
The mystery endured, until, recently, a global consortium of scientists from Singapore, the US, China, India, Russia, Japan, Indonesia, the Czech Republic and Australia decided to work together to figure out where the bug’s roots really lay. The researchers collected samples and compared DNA sequences until it was confirmed, in this year’s report, that the German bug’s ancestors had in fact been Asian.
Blattella germanica had originally been Blattella asahinai.
It had travelled west, to Europe. It had travelled east too, via Dutch traders and British East India Company officers making their way between new colonies in South-East Asia. It had crawled and evolved to settle around the world.
In another interesting twist, the evolution of housing would work perfectly for it too.
As home improvement in the 18th and 19th centuries took plumbing indoors, and as heating went electric, cockroaches found food galore, and comfy nooks, in pipes, drains, lofts and closets.
This allowed the Asian-German cockroach “to colonise regions that had been previously inaccessible due to… poor cold tolerance,” the report states.
Since we’re on the subject of pests, we might as well mention that the “Norway” rat similarly colonised the world, heading out further and further from its original home in central Asia, likely China, amid a boom in international trade and maritime activity.
And, as Wknd reported in a previous story, the cat would follow the rat — but from the Mediterranean Basin outwards — as famished sailors enlisted local felines to help keep rodent populations in check. The cats, presumably bored, stepped out at various ports along the way, and so it is that most of the world’s house cats have DNA traceable to this region.
Well, that’s your treat for getting this far. Click here for the rest of that story.