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Your Bed Is Dirtier Than a Chimp’s

Human beds have far more bacteria associated with skin, saliva and feces than the nests of our primate cousins

Swabbing a chimp's nest. (North Carolina State University)
smithsonian.com

Humans like to pride themselves on their cleanliness compared to other animals, but it turns out, our 700-thread-count Egyptian cotton sheets aren’t as sparkling clean as we might think. A new study in Royal Society Open Science reveals that chimpanzees keep tidier beds, with lower counts of bacteria, reports Jason Bittel at National Geographic.

The filth of human homes and beds is surprisingly well studied. “We know that human homes are effectively their own ecosystems, and human beds often contain a subset of the taxa—or types—of organisms found in the home,” says lead author Megan Thoemmes of North Carolina State University in a press release. “For example, about 35 percent of bacteria in human beds stem from our own bodies, including fecal, oral and skin bacteria.”

But Thoemmes and her colleagues wanted to learn how that microbial ecosystem compares to the sleeping quarters of other mammals. To that end, the researchers used swabs to sample the bacteria growing in 41 chimp nests in Tanzania’s Issa Valley. They also used small vacuums to suck up arthropods from 15 of the nests.

The nests had plenty of bacteria, but most of it was what can be found in the surrounding forest habitat. Only 3.5 percent of the bacteria species came from the chimps themselves, including bacteria from saliva, feces, or skin. That's an order of magnitude less than human beds.

Parasites like fleas and lice were also found at extremely low levels. “There were only four ectoparasites found, across all the nests,” Thoemmes tells Tim Walker at The Guardian. “And that’s four individual specimens, not four different species.”

This cleanliness was surprising. “We expected to see a lot of ectoparasites and a lot of fecal bacteria, because there’s been a lot of evidence showing that fecal bacteria builds up in the fur of chimpanzees,” Thoemmes tells Bittel.

The study doesn’t mean chimps, who rarely take hot showers and are not known to operate washing machines, are really cleaner than humans. Chimps build a new nest about 30 feet off the ground to sleep in every night, meaning there’s not enough time for all their personal filth to build up.

Humans, on the other hand, tend to sleep on the same sheets night after night, accruing bacteria over time. Then there are our mattresses and pillows, which collect massive amounts of dust mites and dead skin over the years.

Also, while chimps sleep among environmental bacteria from the surrounding forests, humans have more or less eliminated outside bacteria from our sleeping quarters, meaning the stuff that comes from us makes up a bigger percentage of the filth. And in the long run, that may not be a good thing. “[Humans] have created sleeping places in which our exposure to soil and other environmental microbes has all but disappeared, and we are instead surrounded by less diverse microbes that are primarily sourced from our own bodies,” the authors write in the study.

Less exposure to this bacteria and other environmental factors may lead to allergies, asthma and autoimmune disorders. Known as the “hygiene hypothesis,” the idea is that humans in industrialized nations have become too clean, and our bodies are not being exposed to the common germs, allergens and other things that “teach” our immune systems how to properly react.

“In some ways, our attempts to create a clean environment for ourselves may actually make our surroundings less ideal,” Thoemmes says in the press release.

The solution? Some studies suggest visiting farms or living with pets can protect against some autoimmune disorders. Or you can go to extremes like anthropologist Fiona Stewart, who spent six nights in a chimp's nest to understand how they work.

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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