25,000-Year-Old Teeth Reveal the World’s Oldest Drug Habit

Two ancient skulls from an Indonesian island carry a strange, telltale kind of damage: deep grooves worn into the teeth by something people did to themselves, over and over, for most of their adult lives. That damage has now pushed back the known history of habitual drug use by tens of thousands of years.

Grooves That Told a 25,000-Year-Old Story

The world’s oldest known habitual drug use has been traced to the Indonesian island of Sulawesi, where ice age hunter-gatherers sucked on betel nuts, palm seeds containing a neuroactive substance, according to a new study published in the journal Science Advances. Researchers made the discovery after studying unusual grooves in the teeth of two prehistoric hunter-gatherers, caused by regularly sucking on betel nuts, Areca catechu, likely for relief from toothache pain.

The partial skeletons of the two people were found on Sulawesi, though their lives were separated by thousands of years. One, a man who died between roughly ages 40 and 50, lived between 25,000 and 16,000 years ago, a period roughly corresponding to the Last Glacial Maximum, the coldest phase of the last ice age, even though Sulawesi itself was never covered in ice. The second individual, whose sex could not be determined, lived on the island between 7,600 and 6,300 years ago, and died at a similar age.

A Numbing Nut That Made Things Worse

Betel nuts contain a neuroactive compound called arecoline, which produces a powerful stimulant effect when chewed together with slaked lime, or calcium hydroxide. But this earlier method, directly sucking on the intact nut without any lime, would have done something more limited: simply numbing the mouth.

The dental damage on both individuals was severe enough that researchers concluded they must have sucked on betel nuts almost continuously throughout their lives. The habit doesn’t appear to have solved their underlying problem. “The more they sucked on the nut to relieve toothache, the worse that the damage to their teeth became,” said study first author Adam Brumm, an archaeologist at Griffith University in Australia. The grooves progressively deepened over time, and in one individual, they eventually exposed the tooth’s inner pulp cavity. “It would have been excruciatingly painful,” Brumm said.

Confirming the Effect in the Lab

After identifying betel nut use as the likely cause of the grooves, researchers still needed to confirm that sucking on the intact nut, a behavior not previously documented, actually produced a neuroactive effect. To test this, they used genetically engineered frog eggs fitted with human neuroreceptors, which did reveal a neuroactive response. Researchers then examined samples taken directly from the ancient teeth, which turned up traces of betel nut use, confirming the connection archaeologically as well as biochemically.

A Habit That Still Exists Today, With Serious Risks

Betel nut, also called areca nut, remains widely used today across parts of South Asia and Oceania. Modern users typically mix it with slaked lime to create a chewable wad known as a quid, producing a strongly addictive stimulant effect. An estimated 600 million people worldwide use betel nut quids today. The practice carries serious health risks: arecoline is carcinogenic, quids are frequently mixed with tobacco, and long-term users are often diagnosed with mouth cancer.

According to the study, the addition of slaked lime likely came much later than the simple sucking behavior documented in the ice age skeletons. Researchers believe lime was probably incorporated during the Neolithic period, roughly 4,000 years ago on Sulawesi, around the same time slaked lime was being added to pottery clay to prevent shrinking and cracking during firing. “It now seems probable that betel chewing as we know it evolved from a much simpler, older practice of just sucking on the intact nut,” the researchers wrote.

Predating Farming by Tens of Thousands of Years

The earlier of the two betel-sucking individuals lived well before the Neolithic period began, not just on Sulawesi, but even before agriculture emerged in the Fertile Crescent roughly 12,500 years ago. That timing matters for a long-running debate in archaeology over whether people began using neuroactive plants as drugs before or after farming was invented. According to Brumm, this new evidence shows that psychoactive drug use happened thousands of years earlier than the introduction of agriculture anywhere in the world.

Betel sucking isn’t the only ancient example of plant-based drug use researchers have documented, though it may be the oldest tied specifically to habitual, addictive use. A 2017 study found that Neanderthals used the bark of poplar trees, which contain salicylic acid, a natural form of the active ingredient in aspirin, for its pain-relieving properties. Ten-thousand-year-old traces of pollen from a psychedelic cactus have been found in Peru, and 13,000-year-old residues of alcoholic beer have turned up in Israel. What sets the Sulawesi find apart, according to Brumm, is that it represents the earliest known evidence specifically of habitual use of a plant-based drug, repeated, compulsive use over an extended period, rather than a single or occasional documented instance.

Independent Praise for a ‘Fantastic Piece of Research’

Elisa Guerra Doce, a prehistoric archaeologist at the University of Valladolid in Spain who studies the prehistoric use of plants as neuroactive drugs and was not involved in the study, called it “a fantastic piece of research.” She said the new study provides “particularly compelling and direct evidence for the antiquity of drug use.”

“In the specific case of betel nuts, the findings are especially significant because they also reveal the prehistoric roots of a deeply established cultural practice in Southeast Asia and the Pacific,” Guerra Doce said. She added that the discovery also illustrates how prehistoric people on Sulawesi explored their natural environment and recognized that it offered not just food and medicine, but “substances that became integrated into social and cultural traditions over thousands of years.”

A Remedy Likely Used by Many, Documented in a Few

Brumm suggests that people of all ages likely used betel nuts as a remedy for toothache throughout prehistoric times, but the telltale dental grooves only became visible in individuals who lived long enough, and used the nuts heavily enough, to develop a genuine dependence on the practice. That detail suggests the two skeletons studied here may represent a much wider, largely invisible pattern of self-medication stretching across many generations of Sulawesi’s ice age and early Holocene inhabitants, most of whom left no comparably obvious trace of the habit behind.

Sources

Live Science, citing Brumm, A. et al., Science Advances (2026)