Over the years, excavations at Chagyrskaya Cave in southwestern Siberia have unearthed an assortment of Paleolithic treasures, including heaps of tools fashioned from stone and bone, alongside fossils from the easternmost population of Neanderthals.
And now, in a study published Wednesday in the journal PLOS One, scientists describe the latest discovery from the site — a Neanderthal molar with a depression that they believe is evidence of an ancient invasive dental procedure. "Basically a root canal," says John Olsen, an archaeologist at the University of Arizona and a co-author of the report.
"This [hole] was created by a stone tool handled by a Neanderthal between the thumb and the forefinger," he says. The tool was used "to rotate that on the chewing surface of the tooth to expose the pulp and clean it out."
"We think this is an open and shut case," he adds.
Rachel Kalisher, a bioarchaeologist at UC San Diego who wasn't involved in the research, says it's a clever finding. "They did a lot of great work and they have beautiful data presented," she says. And she agrees the hole was likely produced by a stone tool, but she can't be sure that it was done intentionally.
"It's certainly believable," she says. "But I'm not sure that the evidence that they provide is necessarily the smoking gun."
A small tooth with a big message
For a rainy month and a half in the summer of 2016, the research team scraped away dirt and rock from the cave floor environment, using scalpels and little knives, while drops of water from the cave ceiling fell on their heads.
But working there is usually worth the discomfort. "It is the richest collection in this part of the Eurasia," says Ksenia Kolobova, an archaeologist at the Institute of Archaeology and Ethnography, Siberian Branch of the Russian Academy of Sciences and an author of the new paper. "I think it was like a dream of the archaeologist."
Towards the end of that time, they found a handful of Neanderthal finger and toe bones, along with teeth some 59,000 years old, including that adult molar.
"When you find it, it's very dirty," says Kolobova. After cleaning the tooth, she noticed a deep hole on the biting surface, something that could have been caused by any number of things. Kolobova later showed the molar to a colleague of hers, dental anthropologist Alisa Zubova, a specialist in ancient teeth.
"At the very beginning, she suspected that the cavity inside the tooth — it's not very natural," says Kolobova.
The research team examined the molar with a micro-CT scan and a scanning electron microscope. The hole occupied the entire volume where the pulp would have been. They noticed numerous microscopic radial grooves that they believed may have been artificially created by drilling into the tooth — to deal with a cavity, perhaps.
To see whether their hypothesis was plausible, the team mimicked the procedure on a few modern human teeth using a replica of what they believe to have been the stone tool, including one donated by one of the researchers. There were "a lot of joke[s] about her impact in the article!" says Kolobova.
These experiments successfully duplicated the same geometry and abrasion observed in the ancient tooth, bolstering the researchers' conclusions. Cavities were rare among Neanderthals, but the scientists believe the molar reveals an ability by these hominins tens of thousands of years ago to execute a precise dental procedure. Subsequent wear on the tooth suggests the individual lived on after the intervention.
"The fact that someone had that knowledge, perhaps a person who made stone tools of the type necessary that would be fine enough to drill into this tooth and then have this manual dexterity to perform that task, I think is what makes this really interesting," says Olsen.
A question of dental intention
Olsen explains that if true, this suggests a degree of cooperation between individuals. "If I'm the one with the bad tooth," he says, "who am I going to trust to do this?" In addition, the patient may have needed to understand that although they were about to endure a large amount of discomfort, the relief on the other side would be worth it.
"[This] tooth is a piece of that puzzle which informs us in a much broader sense of the relationship among these people," says Olsen.
Kalisher, the bioarchaeologist who didn't participate in the study, appreciates the contribution. "They are thinking broadly about what could be causing these appearances," she says. "And then they use a bunch of deductive reasoning and experiments to scratch things off one by one."
Still, she says that a hole in a tooth might have grown larger due to repeated contact and wear with many other things in the environment — though she doesn't rule out a stone tool. With additional evidence, though, she remains open to the idea that Neanderthals were capable of treating cavities.
"I wouldn't be surprised," she says, "because we have all this other evidence that they were very intelligent and able to respond and adapt to different types of situations."
That may include, perhaps, the situation of alleviating a toothache in a way that feels rather human.
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