Scientists examining 25,000-year-old human teeth from Indonesia found grooves so deep and strange that the world's leading dental archaeologists had absolutely no idea what caused them. The answer, it turns out, is that a Stone Age hunter-gatherer spent decades sucking on betel nuts until the habit wore through to the nerve endings. Humanity's relationship with mild intoxicants is, in the most literal sense, older than civilization itself.
The Teeth That Stumped Everyone
On an archaeological dig on Sulawesi, a large island in modern-day Indonesia, researcher Adam Brumm and his team unearthed human remains belonging to someone who lived as far back as 25,000 years ago. The bones were interesting. The teeth were baffling. "There were really strange grooves in the teeth that we couldn't explain," Brumm, a professor of archaeology at Griffith University in Australia, told NPR.
Brumm did what any good scientist does when stumped: he emailed everyone he could think of. Specifically, according to NPR, he contacted "all of the world's leading experts in ancient dental wear." Every single one of them came up empty. Nobody could explain the grooves.
About 20 miles away, they found a second set of teeth from someone who lived up to 8,000 years ago. Same mysterious marks. These grooves were so severe, NPR reports, that they had "exposed the pulp cavity, the nerve center, of several teeth" on multiple teeth. Whatever caused this had been happening, repeatedly, for decades.
Ruling Out Everything Reasonable First
The team went through the obvious explanations methodically. Hunter-gatherers of that period were known to use their teeth as tools, gripping and breaking and stretching things. None of those activities matched the specific pattern. NPR reports that Brumm and his colleagues "ruled out any type of food they might have been eating" and "ruled out the possibility that they were processing plant fibers to make string in their mouth."
The breakthrough came from an unlikely direction: Popeye. Brumm recalled the distinctive dental wear patterns found in European and American laborers from the colonial era who spent their lives smoking clay pipes. "They would have the pipe sticking out of their mouth, Popeye-style," he told NPR. Over decades, the pipe stem carved a perfectly round notch into the teeth. It was a habit. A repeated, compulsive, decades-long habit that left a physical signature in bone.
That reframe changed everything. The Indonesian grooves weren't from tools or food. They were from something these people did constantly, over years, because they wanted to.
Enter the Betel Nut, Stage Left
Betel nuts are the brownish-green seeds of certain palm trees, roughly walnut-sized, and currently used by about 600 million people globally, according to NPR. They are, by any reasonable measure, a big deal. NPR reports they rank as the world's fourth most commonly used mind-affecting substance, sitting just behind tobacco, alcohol, and caffeine. Users report energy boosts, digestive relief, and fresh breath. The medical community notes they can cause tooth damage, heart disease, and oral cancer. The usual story.
Today, betel nuts are typically chewed alongside other chemicals to amplify their stimulant effects. But the groove pattern on the ancient Sulawesi teeth matched sucking, not chewing. Hard, round, abrasive objects, held in the mouth for years. Brumm partnered with Roger Papke, a neuropharmacological researcher at the University of Florida, to find out whether simply sucking on a betel nut could actually do anything to a human brain.
The answer was yes. According to NPR, they soaked whole betel nuts in artificial saliva and introduced the extract to frog egg cells engineered to express human brain receptors. The saliva pulled out arecoline, the nut's active chemical. The brain receptors fired. "We've shown that if you just suck on the nut, there's a physiological reaction that can be released into your bloodstream and then into your brain, and that can alter human brain function," Brumm said.
The Smoking Gun Is in the Tooth Enamel
Matching the shape of betel nuts to the grooves was suggestive. Finding arecoline residue in the actual dental tissue was the clincher. NPR reports that tests of the ancient teeth found traces of arecoline inside them, and crucially, betel nuts are the only known natural source of arecoline, according to Papke. There is no other explanation on the table.
Brumm also did what a certain kind of dedicated scientist does: he tried it himself. "I had to give it a go," he told NPR. Gently gnawing on the outside of the nut releases the juice, he found. "It has this extremely bitter and astringent taste that makes your whole mouth go numb."
That numbing effect, he hypothesizes, is exactly what the ancient Sulawesi hunter-gatherers were seeking. And here is where the story gets genuinely poignant in a dark sort of way. Brumm thinks the repeated sucking slowly wore their teeth down to the nerve. Which would have been agonizing. Which would have sent them reaching for more betel nuts to numb the pain. A 25,000-year-old addiction loop, written in bone.
Context: Humans Have Always Done This
The study, published in the journal Science Advances, adds to a growing body of evidence that drug use is not a modern failure of willpower or a symptom of social decay. It is, by the available evidence, just something humans do. Jose Capriles, an associate professor of anthropology at Penn State who has found evidence of drug use in South America dating back a thousand years, told NPR that "the instinct to experiment and expand our horizons with substances is part of human nature."
Capriles found the new evidence compelling, if not yet conclusive. The arecoline in the dental tissue is hard to argue with. The study represents, as Brumm told NPR, "a chance archaeological discovery that reveals an initial stage in the development of this common drug used today."
The Dingo Take
You are supposed to believe that drug use is a modern social problem, a product of broken families or weak character or whatever the current culture war requires it to be. And then science goes and finds a Stone Age person who ground their teeth down to exposed nerves over decades of betel nut sucking, somewhere in Indonesia, twenty-five thousand years before anyone invented the concept of a drug czar. The habit predates agriculture. It predates written language. It predates pretty much everything we associate with civilization except, apparently, the very human need to make the day slightly more bearable.
What the Griffith University team actually found here is a feedback loop with prehistoric roots: substance numbs pain, substance causes damage, damage creates more pain, substance numbs that pain too. Brumm describes this cycle with what sounds like genuine sympathy for his 25,000-year-old subject. A hunter-gatherer, already dealing with the specific horrors of being a hunter-gatherer in the Pleistocene, developed a soothing habit that slowly destroyed their teeth, which made them lean harder on the habit. If that doesn't sound familiar, you haven't been paying attention.
The real takeaway from this research isn't that ancient people were reckless or primitive. It's that the capacity to find something that makes you feel a little better, and then to do it compulsively until it becomes its own problem, is not a bug in human cognition. It's a feature we've been running for at least 25,000 years. Understanding that honestly, as Capriles suggests, is probably more useful than pretending otherwise. It won't stop anyone from moralizing about it, of course. But the teeth don't lie.
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