Cockroaches: How a South Asian vermin unexpectedly conquered the world

A ubiquitous household pest has unexpected origins. A cockroach that lives in human dwellings all over the world is known as the German cockroach — but it did not come from Germany originally. A study published [May 20] in the Proceedings of the National Academy of Sciences suggests that the creature originated in South Asia and spread globally because of its affinity for human habitats.

[Harvard evolutionary biologist Qian] Tang and his colleagues analysed the genomes of 281 German cockroaches collected from 17 countries, including Australia, Ethiopia, Indonesia, Ukraine and the United States. They used the similarities and differences between the genomes to calculate when and where different populations might have been established.

They found that the closest living relative of the German cockroach is probably the Asian cockroach Blattella asahinai, which is still found in South Asia. Blattella germanica probably split off from it around 2,100 years ago.

Then, around 1,200 years ago, B. germanica hitchhiked west into the Middle East with the commercial and military traffic of the Islamic Umayyad and Abbasid caliphates. It began to spread east from South Asia around 390 years ago, with the rise of European colonialism and the emergence of international trading companies such as the Dutch and British East India Companies. Around a century later, the German cockroach hitched a ride into Europe, and from there spread around the world.

This is an excerpt. Read the original post here