A deep cavity in a single Neanderthal molar from Siberia looks less like random damage and more like a deliberate act of treatment, a finding that pushes invasive dental care far deeper into human history.

The tooth, known as Chagyrskaya 64, came from Chagyrskaya Cave in Russia’s Altai region and dates to about 59,000 years ago. In a study published in PLOS One, Alisa Zubova of the Peter the Great Museum of Anthropology and Ethnography in St. Petersburg and colleagues argue that the tooth was not simply worn down by age, broken by chance, or altered after burial. Instead, they say, a Neanderthal appears to have drilled into a decayed molar to reach infected tissue and ease pain.

That makes the specimen the oldest known evidence of successful dental treatment, and the first such case documented outside Homo sapiens.

“We were intrigued by the unusual shape of the concavity on the tooth’s chewing surface,” Zubova said. “It differed from the normal morphology of the pulp chamber and did not match the typical pattern of carious lesions seen in Homo sapiens. Moreover, distinctly visible scratches suggested that the concavity was not the result of natural damage but of intentional actions.”

The tooth belonged to an adult Neanderthal and was found in an undisturbed layer at the base of the cave sequence. Its crown was heavily worn, but what caught the team’s attention was a large hole in the chewing surface. The opening measured about 4.2 millimeters long, 2.8 millimeters wide, and 2.6 millimeters deep, extending into the pulp chamber where nerves and blood vessels once sat.

The team used microscopes, scanning electron microscopy, micro-CT imaging, Raman spectroscopy, and experimental modeling to figure out what happened.

Several explanations had to be ruled out first. Trauma usually leaves sharp edges and cracks, but this tooth had rounded, smoothed margins. Heavy wear can expose a pulp chamber, especially in older people, but it does not usually widen the opening in the way seen here. Geological damage was also a poor fit. The surrounding deposits showed little sign of disturbance, and the tooth surface did not carry traces of transport or abrasion after burial.

Micro-CT scans pointed instead to deep caries. The researchers found demineralized dentin in and around the cavity, consistent with severe tooth decay. They also noted another likely lesion near a toothpick groove on the side of the same molar.

That second detail matters. This was not the only sign of oral care on the tooth.

The side of the molar carried a well-developed groove that matched repeated toothpick use, and another polished area suggested an earlier stage of the same behavior. Neanderthals have been linked to toothpicks before, but this case went much further.

To see whether a stone tool could produce the same kind of cavity, the team ran a series of experiments on three modern human molars. They made small perforators from local jasper, the same sort of raw material available at Chagyrskaya Cave, and tried two approaches: scraping and rotating.

Scraping did not work well at first. Rotational drilling did.

Using hand-held stone points, an experienced experimenter was able to penetrate dental tissue quickly and create depressions with microscopic grooves that matched those in the Neanderthal tooth. One experimental run took a little over five minutes. Another took about 35 minutes. A third, which reached the pulp chamber, lasted roughly 50 minutes.

Lydia Zotkina said the match between the original tooth and the test samples was clear. “The findings demonstrate that drilling a carious lesion using a sharp, thin stone tool is entirely effective, permitting the rapid removal of damaged dental tissue.”

She later summed up the study’s key point even more directly: “First, the concavity on Chagyrskaya 64 is not natural. It was created intentionally by a human hand, specifically by a Neanderthal, using a small, pointed lithic tool, likely a perforator made of local jasper.”

The shape of the cavity suggests it formed in stages, probably through three partly overlapping drilling attempts. Fine striations on the inner walls run parallel to the cavity edges, fitting a rotating motion. Some of those marks were later smoothed by wear, which indicates the individual kept using the tooth after the intervention.

That continued wear is one of the strongest clues that the person survived the procedure and did not lose the tooth immediately.

This would not have been a small undertaking.

The mouth is a cramped place to work, the tooth was likely inflamed, and the procedure must have hurt badly. Yet the authors argue that removing decayed dentin and exposing the pulp may have relieved the pain that came from infection, at least temporarily, by speeding the breakdown of nerves and blood vessels.

The case also hints at a striking level of practical judgment. Someone had to identify the tooth as the source of pain, choose a pointed tool, and apply it with controlled force. Whether the work was self-treatment or help from another person remains unclear, and the team says the evidence cannot settle that question.

Still, the operation required more than chance.

“Treating a carious tooth is not just feeding or guarding someone,” Ksenia Kolobova said. “It requires diagnosing the source of pain, selecting an appropriate tool, performing a painful, invasive action, and persisting despite the patient’s discomfort.”

The researchers stop short of claiming a formal medical tradition. Caries was rare among Neanderthals, and the authors say it would be hard to argue that this specific treatment was widely taught across generations. But they do see the tooth as evidence of advanced cognition, fine finger control, and a deliberate attempt to repair a diseased body.

Zubova put it in especially stark terms. “Our findings show that understanding the causes of toothache from caries and knowing how to treat it was already possible tens of thousands of years ago, it just never became common.”

The tooth gives archaeologists a new way to think about Neanderthal care. Earlier finds had already shown that injured or frail Neanderthals sometimes survived long enough to suggest support from others. This molar adds a more active form of intervention, one aimed at a specific physical problem and carried out with a tool.

It also suggests researchers may have overlooked similar evidence elsewhere. The team hopes other collections of Neanderthal teeth and bones will be reexamined for subtle traces of treatment. They also want to look more closely for possible plant-based pain relievers or antiseptic materials, though Raman spectroscopy on this tooth found no residues beyond dentin-related compounds.

For now, one worn molar from Siberia has opened a new line of inquiry. It suggests that long before dentistry became common, at least one Neanderthal knew enough to go after the source of a toothache and had the nerve to see it through.

Research findings are available online in the journal PLOS One.