Though often hidden behind closed lips, teeth do a lot of heavy lifting in daily life. They’re the pearly whites flashed for smiles, the sharp powerhouses that grind our food. Our teeth can also take the place of tools, removing pen caps, tearing open bags of chips, and snipping tags off new clothes. Dentists decry the practice, but it really comes in handy—literally: Sharp-edged and stable, teeth often function as well as fingers, earning the mouth the moniker of “third hand.” “I use my mouth all the time when both my [actual] hands are tied up,” says biological anthropologist Kristin Krueger of Loyola University Chicago. “Sometimes, it’s the only way to get things done.” Krueger’s not alone. Plenty of modern humans join her in this convenient form of dental dexterity—and that’s apparently been the case for tens of thousands of years.

Reporting today in the journal PLOS ONE, Krueger and her colleagues have found that our early modern human ancestors also treated their teeth as tools, perhaps using them to support their hands in grasping objects, softening wood or fibers, or preparing animal hides for clothing. Though this strategy has long been known in Neanderthals, it’s often been dismissed as a “primitive” behavior in the fossil record, restricted to lineages without the sophistication to fashion external tools. But the new study, which shows similar wear patterns on Neanderthal and early modern human canines and incisors (teeth at the front of the jaw) takes a big bite out of that antiquated idea. “In many cases...using teeth as tools was likely a clever, expedient thing to do,” says Debbie Guatelli-Steinberg, an anthropologist at Ohio State University who wasn’t involved in the study. The findings also add to the growing list of traits shared by Neanderthals and our early modern human ancestors—two groups that, despite their radically different evolutionary fates, appear to have interacted with their surroundings in very similar ways. “We’re still caught up with this idea of the behavioral revolution: that anatomically modern humans are so much better [than other lineages that died out],” says Bruce Hardy, a paleoanthropologist and Neanderthal expert at Kenyon College who wasn’t involved in the study. “But it’s becoming increasingly difficult to stick with that line.” Modern humans (left) and Neanderthals (right) had their fair share of anatomical differences (including the size, shape, and features of their skulls). But years of research have shown that, contrary to prior belief, they had many behavioral similarities. Image Credit: hairymuseummatt, DrMikeBaxter, Wikimedia Commons Neanderthals first became known to researchers in the mid-1800s, after a partial, stocky skeleton bearing a thick brow ridge on its skull was unearthed in Germany’s Neander Valley. Scientists were quick to describe the newly dubbed Homo neanderthalensis as a species of hunched, barbaric beasts—a “lesser” lineage that had been quashed in the evolutionary race against the well-postured, intellectually savvy Homo sapiens. The Neanderthal narrative has since evolved. In recent years, a deluge of studies have shown that Neanderthals weren’t the boorish brutes they were once thought to be. Like early modern humans, they crafted stone tools and harnessed fire to cook complex meals. They concocted medicines to treat the injured and sick, and may have even gone to great lengths to bury their dead. Some researchers even believe Neanderthals and modern humans aren’t separate species at all. Whatever their differences, the two groups were certainly close enough to interact, and even interbreed—ancient rendezvous that can still be detected in the DNA of people living today.

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But old stigmas die hard. Part of the longstanding stereotype of Neanderthals is their “uncouth” practice of grasping and clamping objects with their teeth, evidenced by the severe amount of wear and tear on their fossilized canines and incisors. “They had tools, but the idea was that they weren’t sophisticated enough to not use their teeth, too,” Krueger says. Because we’re still around and they’re not, she says, many researchers assumed that early modern humans—our direct ancestors—must have been doing “something better.” Until now, though, little had been done to actually check if that was true. So Krueger and her colleagues put the theory to the test. The upper jaw and teeth of an infant Neanderthal, unearthed from the Schmerling Cave in Belgium. Image Credit: Tanya Smith, Griffith University When she and her team compared casts from 45 Neanderthal and 30 early modern human teeth under a microscope, they found that the two groups’ dental wear patterns were pretty much identical. Both sets of chompers carried haphazard scratch marks: some vertical, from the up-and-down motion of biting into food, but also some horizontal, likely from grasping objects that were tugged back and forth. On average, the two sets of teeth also bore similarly sized grooves and divots. The depth of these pockmarks, Krueger says, is a proxy for bite force, which increases as teeth take on more heavy-duty functions. All told, this suggests that on a day-to-day basis early modern humans and Neanderthals were doing comparable things with their teeth—results that came as a surprise to Krueger. “I was expecting to see that early modern humans weren’t [doing this],” she says. “But when I ran the numbers...I really had to shift my frame of reference.” Actually nailing down what our predecessors were sinking their teeth into, however, is a bit complicated. Animal hides and plant fibers don’t have the same staying power as skeletal fossils—which means the nature of these materials, and how they were treated, has to be inferred from only the marks they left behind. But Krueger and her team found that the marks on the ancient teeth resembled those from the dentition of the Tigara, an indigenous Arctic population that inhabited what’s now Point Hope, Alaska, between 750 and 250 years ago. The Tigara are one of many modern groups known to have frequently employed the “third hand,” using their teeth while processing animal hides or softening sinew threads for weaving. Though it’ll be tough to confirm, it’s possible that Neanderthals and early modern humans engaged in similar practices long ago—or at least close analogs befitting of the time and place they lived in, Krueger says. A set of recent modern human teeth from Amarna, Egypt. Image Credit: Courtesy of Kristin Krueger, Loyola University Chicago Though these behaviors are well-documented in ethnographic records of the Tigara and several other populations from around the globe, these people—and the innovative things they did with their teeth—haven’t typically been considered representative of modern humans. This oversight is perhaps indicative of scientific racism, the failure of anthropologists to be culturally sensitive and inclusive to non-Western practices, Krueger says. “We’re educated to not put [non-food] items in our mouths and bite down on them,” says Tanya Smith, a biological anthropologist and teeth expert at Griffith University in Australia who wasn’t involved in the study. “Doing that contradicts what we think of as hygienic...we imagine it as a verboten behavior.” As such, the findings might be viewed as progressive, rather than regressive, and elevate the idea of teeth as tools, Krueger suggests. (As of the afternoon of November 27, representatives of Alaska’s North Slope Borough could not be reached for comment.) Uncovering and analyzing more dental samples will continue to build upon the picture that’s emerging, Smith says. While the Neanderthal teeth used in the study come from all over western Eurasia, spanning a period of roughly 200,000 to 40,000 years ago, the early modern human dental set is sparser, clustering mostly within European sites from the last 40,000 years. It would be fascinating, Smith says, to get a glimpse of the teeth of early modern humans before they left Africa—a time more contemporary with Neanderthals. It’s still unclear why the Neanderthal lineage fizzled out while ours persisted. And the use of teeth might not have had anything to do with it. “There may be many other behavioral differences [between us and Neanderthals],” Guatelli-Steinberg says, “but this wasn’t one of them.”

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