The four Neanderthal teeth showing signs of toothpick use, including the twisted premolar (indicated by the arrow). David Frayer, University of Kansas

Neanderthals practiced a kind of “prehistoric dentistry”, according to research published in the Bulletin of the International Association for Paleodontology.

The research, conducted by anthropologist David Frayer from the University of Kansas in the US and colleagues, reveals that the teeth from a 130,000 year-old Croatian Neanderthal show “definitive” evidence of being scraped with a toothpick. Other types of tooth manipulation are also clear.

Frayer and colleagues studied four loose teeth assumed to be from the same person, originally excavated from a site at Krapina in Croatia more than 100 years ago. {%recommended 845%}

Using visual observation – unaided and through a microscope – the team identified clear grooves made by some form of toothpick, together with other scratches in the dentin and enamel of the teeth.

On one level, the discovery is nothing special. Many previous studies have identified similar grooves on the teeth of several types of early hominid, dating as far back as two million years.

However, Frayer’s team established that one of the teeth from their target Neanderthal – dubbed Krapina Dental Person (KDP) 20 – was probably set awkwardly in the lower jaw (which is missing) and thus very likely painful.

“The scratches indicate this individual was pushing something into his or her mouth to get at that twisted premolar,” Frayer says.

If this is correct, the finding clears up a persistent mystery in the field in of paleodontology – the study of ancient teeth. For although toothpicks have been shown to be widespread across hominid species, the reasons why they were popular have remained unclear.

Theories abound, Frayer and colleagues write in their paper. Many suggest they were used to relieve discomfort – say, by dislodging material stuck between teeth – while others speculate they were used to promote “fibre processing and saliva jetting”.

“Yet,” the authors add, “they also occur with no signs of oral pathology, so they may be idiosyncratic, the product of a nervous behavior.”

They conclude that the KDP 20 evidence, however, is consistent with “palliative measures to ‘treat’ … dental problems”.

Frayer notes that this is the first time that a set of teeth has carried enough distinctive markings and clear enough signs of abnormality to allow the conclusion that Neanderthals used tools as a way of relieving dental pain. However, he adds that the finding is not surprising.

“It fits into a pattern of a Neanderthal being able to modify its personal environment by using tools,” he says.

“Because the toothpick grooves, whether they are made by bones or grass stems or who knows what, the scratches and chips in the teeth, they show us that Neanderthals were doing something inside their mouths to treat the dental irritation. Or at least this one was.”