A close look at Neanderthal dental records has shown that the ancient humans used a plant-based “aspirin” to treat pain and illness.

Ancient DNA found in the dental plaque of Neanderthals—our nearest extinct relative—has provided new insight into their behavior, diet and evolutionary history, including the use of painkillers.

An international team led by the University of Adelaide’s Australian Centre for Ancient DNA (ACAD) and Dental School, along with the University of Liverpool in the U.K., have revealed the complex differences between Neanderthal groups and knowledge of medication.

“Dental plaque traps microorganisms that lived in the mouth and pathogens found in the respiratory and gastrointestinal tract, as well as bits of food stuck in the teeth – preserving the DNA for thousands of years,” lead author Laura Weyrich, Ph.D., ARC Discovery Early Career Research Fellow with ACAD, said in a statement.

“Genetic analysis of that DNA ‘locked-up’ in plaque, represents a unique window into Neanderthal lifestyle – revealing new details of what they ate, what their health was like and how the environment impacted their behavior.”

The research team analyzed and compared dental plaque samples from four Neanderthals ranging from 42,000 and 50,000 years old—the oldest dental plaque ever analyzed—found at the cave sites of Spy in Belgium and El Sidrón in Spain.

According to Cooper, some of the results of the study were surprising.

“One of the most surprising finds, however, was in a Neanderthal from El Sidrón, who suffered from a dental abscess visible on the jawbone,” Cooper said. “He was eating poplar, which contains the pain killer salicylic acid (the active ingredient of aspirin), and we could also detect a natural antibiotic mold (Penicillium) not seen in the other specimens. Apparently, Neanderthals possessed a good knowledge of medicinal plants and their various anti-inflammatory and pain-relieving properties, and seem to be self-medicating.

“The use of antibiotics would be very surprising, as this is more than 40,000 years before we developed penicillin,” he added. “Certainly our findings contrast markedly with the rather simplistic view of our ancient relatives in popular imagination.”

Neanderthals, ancient and modern humans also shared several disease-causing microbes, including the bacteria that causes dental caries and gum disease. The recently discovered plaque allowed the reconstruction of the oldest microbial genome yet sequenced—Methanobrevibacter oralis, a commensal that can be associated with gum disease.

The genome sequence suggests that Neanderthals and humans were swapping pathogens as recently as 180,000 years ago, long after the divergence of the two species.

The team also discovered how rapidly the oral microbial community has altered in recent history.

The composition of the oral bacterial population in Neanderthals and both ancient and modern humans correlated closely with the amount of meat in the diet, with the Spanish Neanderthals grouping with chimpanzees and human forager ancestors in Africa.

However, the Belgian Neanderthal bacteria were similar to early hunter gatherers and close to modern humans and early farmers.

“Not only can we now access direct evidence of what our ancestors were eating, but differences in diet and lifestyle also seem to be reflected in the commensal bacteria that lived in the mouths of both Neanderthals and modern humans,” professor Keith Dobney, from the University of Liverpool, said in a statement. “Major changes in what we eat have, however, significantly altered the balance of these microbial communities over thousands of years, which in turn continue to have fundamental consequences for our own health and well-being.

“This extraordinary window on the past is providing us with new ways to explore and understand our evolutionary history through the microorganisms that lived in us and with us,” he said.