The DNA found in the dental plaque of provided remarkable new insights into the behaviour and diet of the Neanderthals, researchers said.
Researchers from University of Adelaide in Australia and University of Liverpool in the UK, unveiled the complexity of Neanderthal behaviour, including dietary differences between different 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," said Laura Weyrich, from University of Adelaide's Australian Centre for Ancient DNA (ACAD).
The team analysed and compared dental plaque samples from four Neanderthals found at the cave sites of Spy in Belgium and El Sidron in Spain.
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These four samples range from 42,000 to around 50,000 years old and are the oldest dental plaque ever to be genetically analysed.
"We found that the Neanderthals from Spy Cave consumed woolly rhinoceros and European wild sheep, supplemented with wild mushrooms," said Alan Cooper, Director of ACAD.
"One of the most surprising finds, however, was in a Neanderthal from El Sidron, who suffered from a dental abscess visible on the jawbone," he said.
"The plaque showed that he also had an intestinal parasite that causes acute diarrhoea, so clearly he was quite sick," he added.
"He was eating poplar, which contains the pain killer salicylic acid (the active ingredient of aspirin), and we could also detect a natural antibiotic mould (Penicillium) not seen in the other specimens," Cooper said.
"The use of antibiotics would be very surprising, as this is more than 40,000 years before we developed penicillin. Certainly our findings contrast markedly with the rather simplistic view of our ancient relatives in popular imagination," he added.
The research was published in the journal Nature.