Bed bugs hitched a ride on Neanderthals and became the first human pest

Bed bugs and humans go way back – possibly further than most people would care to know. Around 60,000 years ago, a few adventurous bed bugs decided to latch onto Neanderthals who were emerging from caves. That moment marked the beginning of a long and successful ride alongside humans.

Meanwhile, their less curious relatives stayed behind with the bats. Those bat-associated bed bug populations didn’t fare as well.

Since the Last Glacial Maximum, roughly 20,000 years ago, their numbers have been decreasing. In contrast, the human-loving bed bugs have only flourished.

Understanding bed bugs – the basics

Bed bugs are tiny, flat insects that feed on human blood, usually while people sleep. They’re reddish-brown, about the size of an apple seed, and incredibly sneaky.

They don’t jump or fly, but they crawl quickly and hide in cracks, mattress seams, or even behind picture frames.

Most people first notice them because of itchy bites or small rust-colored stains on sheets – left behind after the bugs feed.

These pests spread easily by hitching rides on luggage, clothes, or used furniture. Once they’re in your home, they’re tough to get rid of without persistent effort or professional help. They reproduce fast, and a single female can lay hundreds of eggs in her lifetime.

Genetics, bed bugs, and humans

Researchers from Virginia Tech recently took a closer look at this curious split. They compared the full genomes of two genetically distinct bed bug lineages – those that feed on bats and those that feed on people.

The findings show that the bugs associated with humans have a demographic history that closely mirrors our own. This might make them the world’s first true urban pests.

“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, a postdoctoral fellow in the Department of Entomology.

Human society and bed bug populations

The research adds to our understanding of how pest populations might respond as human cities grow. By linking the global expansion of humans with the rise of urban pests like bed bugs, the study could help pinpoint traits that evolved in parallel with urban development.

The data includes a stairway graph showing that bed bug population growth mirrors the spread of humans across the globe.

“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, who is also affiliated with the Fralin Life Sciences Institute.

“The really exciting part is that the human-associated lineage did recover and their effective population increased.”

Environments where bed bugs thrive

The recovery of the human-linked group appears to line up with the early days of large human settlements.

Around 12,000 years ago, cities like Mesopotamia began to form. Humans were clustering together, creating environments where bed bugs could thrive.

“That makes sense because modern humans moved out of caves about 60,000 years ago,” said Professor Warren Booth.

“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.”

As our communities grew, so did the bed bugs’ breeding pool. Their population expanded along with ours.

Two lineages, still one species

Using genome data, the researchers have created a base for future studies of this 245,000-year-old lineage split.

Although the two lineages are genetically different, they haven’t evolved into two separate species. That makes the human-associated lineage a compelling case for studying recent evolutionary changes.

“What will be interesting is to look at what’s happening in the last 100 to 120 years,” said Booth. “Bed bugs were pretty common in the old world, but once DDT [dichloro-diphenyl-trichloroethane] was introduced for pest control, populations crashed.”

Although bed bugs were thought to have been eradicated at this stage, they reappeared within five years – and they had become resistant to the pesticide.

Booth, Miles, and graduate student Camille Block previously identified a gene mutation that might explain this resistance.

Their current research continues to explore how bed bugs evolve at the genetic level, especially when it comes to surviving chemical treatments.

Science, support, and the long view

The project also reflects the benefits of giving researchers the time and support to follow interesting scientific questions, wherever they lead.

“It’s a great resource to have,” said Booth. “We are using it for work investigating the evolution of insecticide resistance and species spread using museum specimens collected from 120 years ago to our present-day samples. I’m very lucky to have that freedom to explore.”

From cave walls to skyscrapers, bed bugs have stayed close to humanity through every major chapter in our story. And thanks to research like this, we’re finally starting to understand just how close that connection really is.

The full study was published in the journal Biology Letters.

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