“When people talk about the Paleo diet, that’s not paleo, that’s just non-carb,” Weyrich says. “The true paleo diet is eating whatever’s out there in the environment.”

One of the El Sidron Neanderthals even seemed to be self-medicating with edible plants. One of his teeth had an abscess, and his plaque contained a parasite that causes diarrhea. But the plaque also contained Penicillium, the mould that produces the antibiotic penicillin, and poplar bark, a natural source of the aspirin-like painkiller, salicylic acid. The Neanderthal’s medical history—both diseases and treatments—were written in his plaque.

Neanderthals were our closest relatives, who lived in Europe before they went extinct 40,000 years ago. They left their DNA behind in people of Eurasian descent, and their bones in various European caves. By analyzing the chemical content of those bones, some scientists concluded that they were apex carnivores, much like polar bears or wolves. But other teams, who looked at the erosion patterns on Neanderthal teeth or plant matter stuck in their plaque, argued that they occasionally ate a lot of plants.

Weyrich’s results matches all of these earlier ones, and portrays Neanderthals as adaptable and versatile. “Those that occupied southern regions with relatively warm climates, consumed different types of foods, including meat and vegetables,” says Luca Fiorenza from Monash University, who was not involved in the study. “But Neanderthals that lived in very harsh conditions, such as northern Europe, were forced to rely on the limited sources available—meat.”

“We need to revamp the view of Neanderthals as these meat-eating, club-toting cavemen,” adds Weyrich. “They had a very good understanding of what foods were available to them.”

“It’s nice that the different types of data appear to match,” says Anne Stone from Arizona State University. And that’s important because “I don’t think we really understand how dietary DNA is incorporated into plaque.” Do some types of food get incorporated more than others, or is it random? How much do you need to eat of something before it shows up? “We don’t know if we’re looking at their last meal or random food debris from the last ten years,” Weyrich admits.

She didn’t actually set out to study Neanderthal diets. She was more interested in the microbes within the plaque. In an earlier study led by Alan Cooper, she and her colleagues looked at plaque from European hunter-gatherers, who lived between 5,450 and 7,500 years ago, and showed that they carried more diverse range of mouth microbes than people in industrialized societies. That discovery pushed them to look at even older samples. As DNA ages, it degrades and shatters, so the team had to invent new methods to recover microbial DNA from their Neanderthals, and to exclude contaminating modern microbes. Their payoff: the very first microbiomes from extinct hominids.