Neanderthals used a natural form of aspirin for pain relief, according to a recent analysis of DNA from the hardened dental plaque of our nearest extinct relatives.

The genetic testing showed that a prehistoric individual who suffered from a dental abscess had been chewing on poplar, whose bark is rich in salicylic acid, a natural pain reliever from which the active ingredient in aspirin was originally derived.

Published in the journal Nature, the research was carried out by 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 UK.

The researchers examined teeth and tartar samples of four Neanderthals from the cave sites of Spy in Belgium and El Sidrón in Asturias, northern Spain.

Ranging from 42,000 to around 50,000 years old, the samples represent the oldest dental plaque ever to be genetically analyzed.

"We can learn things about Neanderthals and their behavior simply from microorganisms in the mouth," lead author Laura Weyrich, ARC Discovery Early Career Research Fellow with ACAD, told Seeker.

She explained that calcified dental plaque, a mineralized deposit of calcium phosphate that adheres to tooth enamel, traps bits of food as well as microorganisms and pathogens from the mouth as well as the respiratory and gastrointestinal tracts, preserving the DNA for thousands of years.

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The samples of hardened plaque revealed that the Neanderthals from Spy Cave in Belgium consumed lot of meat. Their diet included woolly rhinoceros and mouflon, supplemented by the edible grey shag mushroom (Coprinopsis cinerea).

In contrast, the dietary profile of Neanderthals from the El Sidrón cave in Spain contained no sequences that suggested meat consumption. They appeared to have consumed a largely vegetarian diet based on wild mushrooms, pine nuts, and moss.

"We were surprised not to find any remains of meat in the Asturias Neanderthals, given that they were thought to be predominantly meat eaters," said Antonio Rosas, at the National Natural Science Museum in Madrid.