Ancient Indonesian foragers may have used psychoactive nuts 25,000 years ago

Two skeletons pulled from the earth on the Indonesian island of Sulawesi tell a story that reaches back 25,000 years—and it is a story about human beings and their appetite for altered states of mind. The bones belong to foragers who lived long before agriculture, before cities, before writing. What makes them remarkable is not their age alone, but what their teeth reveal: deep, rounded grooves worn into the enamel, some so severe they would have exposed the nerve. Chemical analysis found traces of arecoline, a psychoactive compound, embedded in the tooth tissue itself. The evidence suggests these ancient people were sucking on betel nuts—hard, abrasive seeds from the Areca catechu palm—not once or twice, but habitually, day after day, hour after hour.

One skeleton dated to roughly 7,000 years old. The other was far older: somewhere between 16,000 and 25,000 years in the past. Both showed the same distinctive wear pattern. When Adam Brumm, a researcher at Griffith University's Australian Research Centre for Human Evolution, first examined the teeth, he struggled to explain what he was seeing. "It's like someone had a drill head shaped like a gobstopper and wore away the inner part of the tooth," he said. The answer came from a simple thought experiment: imagine holding a smooth stone in your mouth and moving it from one side to the other, day in and day out. Over time, even the hardest tissue in the human body would yield to that pressure, forming grooves.

Betel nuts are not widely known in Western societies, but they are the fourth most-used psychoactive substance on the planet, after alcohol, caffeine, and nicotine. Roughly one in ten people globally chew them, concentrated heavily across the Asia-Pacific region. Today, the nuts are typically prepared by mixing them with slaked lime—a powder made from burnt shells—which intensifies the psychoactive effect and produces a stronger high. But the foragers of Sulawesi had no such knowledge. Brumm and his team tested whether sucking on raw betel nuts alone could produce a noticeable effect. They soaked the nuts in artificial saliva and found that the liquid soon contained enough arecoline to induce a high, though milder than the modern prepared version. The sensation, Brumm noted from his own experiment, is bitter and astringent. It numbs the mouth. That numbness, he suggests, may have been exactly what these ancient people were seeking.

The research, published in Science Advances, proposes a darker possibility: that the foragers had stumbled into a self-perpetuating trap. Perhaps they began sucking on the nuts as a remedy for toothache. The numbing sensation would have provided relief. But the very act of sucking wore their teeth down further, creating worse pain over time. So they sucked more. The cycle deepened. What started as medicine became the disease itself, and the disease demanded more medicine. It is a portrait of addiction that reaches across 25,000 years.

The discovery pushes back the known history of human drug use significantly. The oldest documented traditions of psychoactive consumption—fermented barley beer and similar drinks—date to roughly 13,000 years ago. These Indonesian foragers predate even that. Elisa Guerra-Doce, an associate professor in European prehistory at the University of Valladolid, called the findings "direct evidence of the antiquity of human drug use." She emphasized that the work represents not only the earliest known evidence of psychoactive plant consumption anywhere in the world, but also proof that betel nut use is not a modern habit or a recent cultural practice—it is a tradition stretching back into deep prehistory, older than agriculture, older than settled life, woven into human behavior for longer than most of civilization has existed.