The Global Conquest of a Persistent Indoor Pest

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Did you know that the cockroach that recently emerged from your sink drain and quickly disappeared under the fridge was most likely a German cockroach? A new study revealed that these nocturnal critters have been pestering people for over 2,000 years in southern Asia.

The study, which was published on May 20 in the journal Proceedings of the National Academy of Sciences, revealed that the journey of insects from scavenging in ancient Asian civilizations to finding shelter under your kitchen floor mirrors significant historical changes in global commerce, colonization, and war.

German cockroaches, scientifically named Blattella germanica, are commonly found in cities across the United States and worldwide. These resilient pests were first documented in scientific records 250 years ago in Europe, which is why they are called German cockroaches, but their exact origin remains largely unknown.

Mandatory Credit: Photo by SHAWN THEW/EPA-EFE/Shutterstock (11989961f) A group of adult Brood X periodical cicadas after shedding their exoskeletons in Alexandria, Virginia, USA, 01 June 2021. After molting, the cicada's body hardens and darkens, then the 17-year-old bug looks for a mate. Trillions of Brood X cicadas are emerging in the Mid-Atlantic region of the US. Brood X cicada emergence in Alexandria, Virginia, USA - 01 Jun 2021

A bunch of grown-up Brood X periodical cicadas in Alexandria, Virginia, USA, are shown after shedding their old exoskeletons. Once they molt, their bodies become tougher and darker, and then these 17-year-old insects start searching for a partner. It's estimated that trillions of Brood X cicadas are making their appearance in the Mid-Atlantic area of the United States. This specific event was captured on June 1, 2021.

Shawn Thew/EPA-EFE/Shutterstock

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Research Journey: Dr. Qian Tang and his team delved into the mystery of how cockroaches spread worldwide. They reached out to scientists and pest control experts globally to collect 281 German cockroach samples from 57 locations in 17 countries. By analyzing the DNA of these specimens, they were able to unravel the evolutionary path of these insects.

Tang, an evolutionary biologist who is currently a postdoctoral research associate at Harvard University, shared that their main goal was to demonstrate how a species can travel alongside humans and how genetics can help fill in the gaps in historical records.

Through analyzing genomic data from samples, Tang made a surprising discovery that the lineage of the modern cockroach actually dates back much further than 18th century Europe. The research revealed that the insect evolved from the wild Asian cockroach, scientifically known as Blattella asahinai, around 2,100 years ago.

Image taken from the Extinct & Endangerd exhibition by Levon Biss, in collaboration with the American Museum of Natural History. The project shines a light upon insect decline and biodiversity, displaying insects that are either already extinct or under severe threat. The photographs by Levon Biss are created from up to 10,000 individual images using microscope lenses and contain microscopic levels of detail to provide the audience with a unique visual experience.

The Extinct & Endangered exhibition by Levon Biss, in partnership with the American Museum of Natural History, showcases insects that are either extinct or at risk of extinction. Through the use of up to 10,000 individual images and microscope lenses, Levon Biss's photographs capture intricate details at a microscopic level, offering viewers a one-of-a-kind visual experience.

Levon Biss/American Museum of Natural History

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Cockroaches and trade routes

Tang and his colleagues believe that around that time, people in what is now India or Myanmar started planting crops in the natural habitat of the Asian roach. The insects then adapted by changing their diets to include human food, eventually moving into human households.

Approximately a thousand years later, due to increased trade and military activities between southern Asia, the Middle East, and later Europe, domesticated cockroaches began spreading westward. It is likely that they hitched rides in soldiers' and travelers' lunch baskets. According to genetic analysis by the study team, the insects first entered Europe around 270 years ago. This estimate aligns with when the famous Swedish geneticist Carl Linnaeus first described them in 1776, shortly after the Seven Years' War that took place in Asia, Europe, and North America. The study also revealed that the cockroaches made their way from Europe to the Americas about 120 years ago.

German cockroaches have a unique behavior of communicating with each other to find food. This behavior is not seen in other cockroach species, according to Dr. Qian Tang, a research associate at Harvard University.

"Insects are deeply intertwined with human culture," according to Dr. Jessica Ware, who works as a curator of invertebrate zoology at the American Museum of Natural History in New York City. She was not directly involved in the study but shared her insights. Dr. Ware mentioned that historically, there has been awareness of people unintentionally transporting many pest species. The spread of German cockroaches, for example, was likely facilitated by transatlantic trade routes. The exciting part was when researchers were able to confirm this through the genetic makeup of these insect populations.

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According to Ware, humans have unintentionally been creating ideal living conditions for cockroaches in their homes. Factors like indoor plumbing and heating, which have contributed to human comfort and development, have also inadvertently benefited cockroaches. Ware pointed out that the sewer systems running beneath cities serve as a perfect food source for cockroaches.

Tang plans to sequence the full genomes of his hundreds of specimens to understand how German cockroaches have adapted so successfully to living with humans. He is curious about their fast evolution and insecticide resistance, wondering if it is a genetic trait that has been uncovered due to human activities.

In addition to their adaptability, German cockroaches also display social behaviors, such as communicating with each other to locate food. Tang is interested in exploring whether this ability is another survival skill that roaches have developed in response to human presence.

Amanda Schupak is a science and health journalist in New York City.

Editor's P/S:

I found this article fascinating, especially the revelation that German cockroaches have been around for over 2,000 years. It's amazing to think that these tiny creatures have been traveling alongside humans for centuries, adapting to our changing lifestyles and spreading to every corner of the globe. The study's findings highlight the interconnectedness of humans and the natural world, and how our actions can have far-reaching consequences for both ourselves and other species.

It's also worth noting that German cockroaches are just one example of the many pest species that have benefited from human activities. As we continue to alter the environment and create new opportunities for these creatures, it's important to be aware of their potential impact and to take steps to mitigate their spread. By understanding the evolutionary history and behaviors of pest species, we can develop more effective strategies for controlling their populations and minimizing their impact on our lives.