The evolutionary mystery of the German cockroach

I became interested in the evolution of these species coadapted to human structures because of my work on recent human evolution. Many human populations have been adapting to some very extreme environments over the last few thousand years. From the high Andes Mountains to the hot Kalahari Desert, and from the high Arctic to the floating villages of southeast Asia, people have been adapting to extremes. Inventing new cultural practices is one way that people push physiological boundaries. Houses, shelters, clothing, food storage bins, water containers: all these help to moderate extremes. They also create microhabitats that other species colonize, from mice to microbes.

One of the most striking examples of adaptation to the environments built by humans is the German cockroach. This species, Blattella germanica, is one of around a half dozen cockroach species that commonly inhabit human structures. Most, like the American cockroach and Oriental cockroach, are a lot bigger in size than German cockroaches, and all of the others can still be found inhabiting natural habitats in the part of the world where they originated. But not the German cockroach. This small species only exists within and nearby human-built structures. Despite what may seem like a huge limitation, the species has been incredibly successful in spreading globally as a 2019 review by Qian Tang and coworkers put it, from Alaska to Antarctica and everywhere in between.

But nobody has had a clear idea of where it came from. It’s a great evolutionary mystery: This is a species most people have encountered somewhere in their homes, places of work, hotels, or restaurants. Yet there seemed to be no trace of its origin.

via johnhawks.net

John Hawks.

This and the following two posts come from The Diff, and interesting substack — TheDiff.co TheDiff is mostly finance but has other stuff as you can see.

Cockroaches are of course disgusting. I kill them when I must but they make a mess when you squish them and spread disease. They are karma sinks as whenever you kill one, you presumably move down in terms of your reincarnation status, though it is unknown how many roaches you have to kill to go from human to say, cat. One hopes a lot. And that’s assuming cats are not higher up in the chain, which I suppose is controversial.