The German cockroach, also known as the common cockroach, is a member of the animal kingdom that brings to mind positive thoughts for few people - hardly even the most enthusiastic animal rights advocates. However, in all its repulsiveness, it is an extremely interesting creature that is entirely dependent on humans, as it is not known to live independently anywhere in the world.
The German cockroach was described by Carl von Linné, who developed the modern system of organism classification. He also suggested that it originated from somewhere else than Europe. And indeed, he was a wise man, for research has shown that the cockroach originated in Asia and has even traced its spread around the world.
By analyzing mitochondrial genes, it has been shown that the German cockroach is most closely related to the Asian cockroach, which was originally described in Japan but has since spread to the United States. The journey of the German cockroach from Asia has been investigated by mapping genomic similarities from 281 samples collected in 17 countries.
Their genetic relationships indicate that German cockroaches achieved global distribution in two waves, both assisted by humans. However, this only began after the ancestors of the German cockroach diverged from the Asian cockroach about 2100 years ago.
This likely happened in India or Myanmar as the cockroaches adapted to eating human food. After mastering this skill, the German cockroach moved to the Middle East about 1200 years ago, coinciding with the expansion of trade and warfare during the two Islamic caliphates, the Umayyads and the Abbasids. The likely means of transportation were bread baskets carried by people.
In the next wave, the species' range expanded to Southeast Asia about 390 years ago, driven by colonial trade by the Dutch and British East India Companies. Finally, trading ships brought the cockroaches to Europe around 300 years ago.
Subsequently, steamships and improved housing – with heating and plumbing creating warm, humid conditions favored by cockroaches – enabled the German cockroach to spread worldwide. The only place left unconquered is Antarctica.
The story of the German cockroach, as briefly described above, illustrates how natural selection takes advantage of opportunities. First, the abundance of food produced by agriculture created a new ecological niche, allowing some cockroaches to specialize in consuming human food.
With the services provided by humans, the cockroaches were then ready to travel with them all over the world. And to adapt to living in the most diverse conditions – as long as there is someone there providing them with bread and warmth.
Previous thoughts on the same topic:
Traditional beliefs turned out to be wisdom
Leaders infected by a parasite
World oceans are filled with previously unknown viruses
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