How much can you learn from Neanderthal plaque? A lot, scientists have discovered: DNA from the plaque provides an amazingly detailed view into the life of our extinct human relatives, including what they ate, how they took medicinal plants to combat disease, and what their mouth bacteria was like. The discovery gives scientists a window into the precious microbial world inside our closest relatives; this information could be used to better understand how bacteria that live inside our own bodies, called microbiome, evolved — and how these microbes affect our health.
The study, published today in Nature, shows the exact foods consumed by five Neanderthal specimens in Europe: woolly rhinoceros, moss, pine nuts, and wild sheep. One individual suffered from a tooth abscess and a stomach bug, and appears to have treated himself using plants that have the same pain-killing component as aspirin, as well as a natural antibiotic. Finally, the scientists analyzed the different bacteria found in the Neanderthals’ mouths, including one that’s 48,000 years old and is still found in our mouths today.
“We can now track [the human microbiome] in time and space, and understand the evolutionary process,” study co-author Keith Dobney, the head of department and chair of human paleoecology at the University of Liverpool, tells The Verge. “We basically have a new window on the past for us, but we also have a way to use that to understand the present.”
Neanderthals lived between about 400,000 to 40,000 years ago in Europe and parts of Asia, where they were eventually replaced by Homo sapiens. Since they were discovered in the 1800s, hundreds of studies have come out about their diet and lifestyles. One study found that Neanderthals ate lots of meat, such as reindeer, woolly mammoth, and woolly rhinoceros. Other studies showed that they were pretty intelligent — they made glue as far back as 200,000 years ago, and built complex structures about 176,000 years ago, way before modern humans were around.
Today’s study adds to our understanding of Neanderthals, and gives direct evidence of what they ate and how they lived. The researchers sequenced DNA from the calcified plaque of five specimens in Europe dated from 42,000 to 50,000 years ago: two from Spain, two from Belgium, and one from Italy. Plaque — the disgusting film coating our teeth — is made of bacteria and bits of food. Analyzing it shows scientists what we eat and what diseases we have. The researchers found that the Neanderthals living in Belgium ate mostly meat, including woolly rhinoceros and wild sheep. The individuals in Spain, however, were on a veggie diet: they ate mushrooms, pine nuts, and moss. (The Italian Neanderthal failed to produce results.)
One specimen in Spain was also found to suffer from a tooth abscess, a painful bacterial infection, as well as a chronic stomach bug that today causes severe diarrhea in people, says Dobney. The plaque on his teeth also contained the DNA of a Penicillin-like fungus (a natural antibiotic), as well as poplar, a plant that has the same pain-killing component of aspirin. That suggests that Neanderthals in Spain were taking medicine when they were sick — a pretty advanced behavior. “The general public view of Neanderthals is a pretty kind of basic, stereotype cartoon version of simplistic knuckle-dragging” cavemen, Dobney says. But that’s changing now. “These were sophisticated relatives of ours.”
The Spanish specimen also preserved the DNA of a 48,000-year-old bacterium that is still found in our mouths today in a slight different form. The Neanderthals must have passed that bacterium to modern humans when the two interbred, Doney says. “They were obviously passing pathogens and microbiome to each other,” he says.
The researchers did the near-complete sequence of this ancient form of Methanobrevibacter oralis; by comparing this ancient bacterium, as well as the other Neanderthal bacteria, with today’s, scientists can better understand how the human microbiome evolved. “This opens a new chapter in understanding the evolution of the commensal bacteria we carry in our [mouths,]” Johannes Krause, the director of the Max Planck Institute for the Science of Human History, who did not take part in the study, writes in an email to The Verge.
The study has some limitations. The DNA analyzed by the researchers is extremely old, and may have been contaminated by the soil in the caves were the specimens were found, Krause says. It’s possible, for instance, that Spanish Neanderthals weren’t actually eating moss, but ancient moss was in the surrounding environment. “Anything from the cave environment could have contaminated the samples,” Krause says. (Dobney says that’s very unlikely, because the DNA of animals, plants, and fungi degrades quickly unless it’s enclosed in some protective environment, like the calcified plaque.) We also don’t have a database of the complete genome of all plants, animals, and bacteria in the world, so the researchers may be mistakenly matching an ancient DNA fragment with a modern organism, while instead it belonged to another organism that’s not in the database yet, Krause says.
The most interesting part of the study is the analysis of the Neanderthals’ mouth microbiome, says Christina Warinner, the co-founder of the Laboratories of Molecular Anthropology and Microbiome Research at the University of Oklahoma. In recent years, scientists have started studying the collection of bacteria and viruses that inhabit our bodies with renewed interest, and we have only begun to understand the role these tiny creatures play in our health and disease. Learning what body bacteria our human ancestors had, and how those bacteria evolved, will help us better understand our bodies today. The study “is an important reminder of how we've really just scratched the surface of the human microbiome, and how much work there is to do to understand the evolution and ecology of this fundamental part of our human biology,” Warinner writes in an email to The Verge.
Dobney agrees. “It’s fantastically relevant to how we understand health and diet today because we can track it in time and space,” he says. Dobney began looking at calcified plaques in the 1980s, when he was in his 20s. But the technology at the time didn’t allow him and his colleagues to really analyze ancient DNA. “I knew this could be really cool,” he says. “But we just couldn’t do it. Nobody believed it could be done and the technology wasn’t really there. It was tantalizingly close.”
That has all changed in the past few years, Dobney says, and the technology has finally caught up with his dreams. “It’s just the coolest science on the planet at the moment, it’s amazing,” he says. “The moral there is, never give up on a good idea.”