Bed bugs are a nuisance that often infect travelers in hotel rooms or used furniture that’s brought into a new home. For thousands of years, bed bugs have enjoyed living off their human hosts, and it may have all started when the bugs spread from bats to our Neanderthal ancestors. 

According to a new study published in Biology Letters, some 60,000 years ago, bed bugs leapt off their bat hosts and onto some unsuspecting Neanderthals that were leaving a cave. Since then, bed bugs that began a relationship with humans have been thriving, likely making them the first human pest. 

However, the bed bugs that remained on the bats didn’t enjoy such a thriving relationship. 

Analyzing Ancient Bed Bugs

The less adventurous bed bugs that stayed on their bat hosts have seen a decline in population, which the research team believes began 20,000 years ago during the Last Glacial Maximum, also known as the Ice Age. 

For this study, the research team compared the complete genome sequence of these two genetically different lineages of bed bugs. The results show that the human-associated lineage followed a similar pattern to its human hosts.

“We wanted to look at changes in effective population size, which is the number of breeding individuals that are contributing to the next generation, because that can tell you what’s been happening in their past,” said Lindsay Miles, lead author and postdoctoral fellow in the Virginia Tech Department of Entomology, in a press release.

Read More: The Fascinating Path of Neanderthal Evolution: Where Did Neanderthals Come From?

Bed Bug Genetics 

Thanks to the new information garnered from this study, researchers can now inform models that could predict how pests and diseases spread with urban development. Understanding the relationship between human and bed bug evolution could also help the research team identify the traits that co-evolved in both species.

“Initially with both populations, we saw a general decline that is consistent with the Last Glacial Maximum; the bat-associated lineage never bounced back, and it is still decreasing in size,” said Miles, an affiliate with the Fralin Life Sciences Institute, in the press release. “The really exciting part is that the human-associated lineage did recover and their effective population increased.”

One of the reasons the human-associated bed bugs may have thrived was the eventual establishment of settlements and cities, like Mesopotamia, about 12,000 years ago. As these cities grew, so too did the population of human-associated bed bugs. 

“That makes sense because modern humans moved out of caves about 60,000 years ago,” said Warren Booth, the Joseph R. and Mary W. Wilson Urban Entomology associate professor, in a press release. “There were bed bugs living in the caves with these humans, and when they moved out, they took a subset of the population with them, so there’s less genetic diversity in that human-associated lineage.”

Bug and Human Co-Evolution 

According to the study, while each of these bed bug lineages has genetic differences, they are still the same species. From this information, the research team is hoping to understand the different genetic alterations of these lineages, and what about them may help bed bugs adapt more easily to a changing world. 

“What will be interesting is to look at what’s happening in the last 100 to 120 years,” said Booth in a press release. “Bed bugs were pretty common in the old world, but once DDT [dichloro-diphenyl-trichloroethane] was introduced for pest control, populations crashed. They were thought to have been essentially eradicated, but within five years, they started reappearing and were resisting the pesticide.”

Booth, Miles, and Camille Block, a graduate student, have already released a separate study that discusses how pesticides affect the bugs less from a specific gene mutation. The more information the research team has on bed bug genomes, the better they can understand the co-evolution of our oldest pest and how it’ll continue to evolve alongside us.

Read More: What Do Bed Bugs Look Like and How Can You Avoid Them?

Article Sources

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A graduate of UW-Whitewater, Monica Cull wrote for several organizations, including one that focused on bees and the natural world, before coming to Discover Magazine. Her current work also appears on her travel blog and Common State Magazine. Her love of science came from watching PBS shows as a kid with her mom and spending too much time binging Doctor Who.