Ancient DNA scraped from Neanderthal skulls reveals that our nearest extinct relative might have self-medicated, with traces of plants containing salicylic acid – the active ingredient in Aspirin – found on teeth.
Published in Nature, a study by researchers from the University of Adelaide in Australia and the University of Liverpool in the UK used DNA from dental plaque samples of four Neanderthals – between 42,000 and 50,000 years old – from the cave sites of El Sidrón in Spain, and Spy in Belgium to gain insight into behaviour, diet, and medicinal practices.
“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,” explains on of the study’s authors, Laura Weyrich from the University of Adelaide.
In conducting their analysis the researchers sequenced genetic material they found on the Neanderthal gnashers and compared the data to samples taken from the teeth of a chimpanzee, as well as modern and ancient humans.
They analysed the results to see what kinds of animal or plant DNA were present on the Neanderthal teeth – a clue to the types of food they were consuming.
It turned out that location made all the difference in terms of diet. Neanderthals from Spy had a taste for rhinoceros, sheep, and mushrooms, while the El Sidrón specimens appeared to have a less meat-intensive diet, preferring instead to snack on moss, mushrooms again, and pine nuts.
The results “support evidence that Neanderthal groups across Europe used multiple subsistence strategies according to location and food availability,” the researchers write.
Of the four specimens tested, the teeth of one of the Neanderthals from El Sidrón showed traces of poplar, a plant that contains the natural painkiller salicylic acid. The researchers also found traces of the fungi Penicillium – which produces the antibiotic penicillin.
Further testing indicated that the specimen was infected with a pathogen known to cause diarrhoea in humans, and was also suffering from a dental abscess. This suggests that Neanderthals may have possessed a sound knowledge of medicinal plants and their various properties.
The team was also able to explore how the microbes in our mouths may have been altered in recent history, by comparing DNA retrieved from the Neanderthals to those on the teeth of the modern and ancient human samples.
They found a correlation between oral bacteria and dietary meat intake. Additional sequencing analysis on the DNA taken from the plaque of the self-medicating Neanderthal led to the the oldest microbial genome every sequenced – Methanobrevibacter oralis, a bacterium associated with gum disease.
Because of slight differences between human-associated M.oralis and the type found in the Neanderthal, the researchers could track the divergence of two strains of the microbe.
They found that they split long after Neanderthals and modern humans themselves diverged, indicating microbial transference continued well after the hominin species became distinct.
Commenting on the novelty of the study, paleoanthropologist Luca Fiorenza from Monash University, Australia, notes that “the innovation here is not the analysis of the dental calculus [plaque] itself, it’s the analysis of the oral bacteria and the DNA preserved within the dental calculus – this has never been done before.”