25,000-Year-Old Teeth Reveal One of Humanity’s Oldest Drug Habits

A pair of ancient human teeth has revealed something researchers did not expect to find buried in an Ice Age cave: evidence that people may have been repeatedly using a psychoactive plant thousands of years before agriculture began.

The strange discovery came from two sets of human remains found in caves in South Sulawesi. Their teeth contained deep, rounded grooves that specialists initially struggled to explain. Chemical analysis eventually pointed toward arecoline, the psychoactive compound found in betel nut.

The Strange Grooves Left Researchers Stumped

Adam Brumm, an archaeologist at Griffith University, was examining a fragment of upper jawbone from Leang Bulu Bettue when he noticed something unusual. The teeth belonged to a forager who died somewhere between 25,000 and 16,000 years ago, yet the enamel contained deep, rounded grooves unlike anything his team could immediately explain. “There were really strange grooves in the teeth that we couldn’t explain,” Brumm said.

The team considered several ordinary explanations. Ancient foragers often used their teeth almost like tools, gripping objects, stretching fibers and opening materials with their mouths. But those activities did not explain the distinctive rounded depressions found in the same areas of the teeth.

Then another set of human remains appeared in a nearby cave. The second individual lived roughly 10,000 years after the first, yet their teeth displayed remarkably similar damage. Both individuals were older than about 35 when they died, suggesting the unusual wear had developed over years rather than appearing suddenly.

A Habit That Left Its Mark On Teeth

The breakthrough came when researchers compared the ancient grooves with a much more recent example of dental wear. People who smoked clay pipes for years could develop a characteristic notch in their front teeth where the pipe stem repeatedly rested. The damage was caused by a habit performed again and again over a long period.

“They would have the pipe sticking out of their mouth, Popeye-style,” Brumm explained. The comparison gave researchers a new way to think about the ancient teeth. Perhaps the grooves were not caused by something the people were eating or manufacturing. Perhaps they recorded something they repeatedly held in their mouths.

That possibility became especially interesting because the caves were located in a region with a long history of betel nut use. Brumm immediately considered the areca palm seed, commonly known as betel nut, as a possible explanation. “I thought, immediately, betel nut is the most likely possibility,” he said.

Chemical Evidence Pointed To Betel Nut

Betel nut comes from the areca palm and contains arecoline, a psychoactive compound capable of affecting the nervous system. Today, betel nut is commonly prepared by combining the seed with betel leaf and slaked lime, creating a mixture known as a betel quid.

Researchers analyzed dental tissue from both ancient individuals and found arecoline inside the teeth. Roger Papke, a neuroscientist at the University of Florida who worked on the research, noted that arecoline has no other natural source.

That chemical evidence connected the two people across a staggering span of time. They lived around 10,000 years apart, yet both appear to have repeatedly exposed their teeth to the same psychoactive plant. Brumm even tried betel nut himself to understand the experience, describing it as having “this extremely bitter and astringent taste that makes your whole mouth go numb.”

The Ancient Habit Could Actually Produce A Drug Effect

There was still an important question. Modern betel nut users usually prepare the seed before chewing it, often adding slaked lime to accelerate the release of psychoactive compounds. The ancient people had apparently been sucking intact nuts, so researchers needed to determine whether that could have produced any meaningful effect.

The team soaked whole betel nuts in artificial saliva and tested the resulting extract on frog egg cells engineered to carry human brain receptors. The experiment showed that compounds released from the intact nuts could interact with those receptors.

“This showed that just sucking on intact betel nuts will release arecoline in sufficient amounts to have a physiological effect,” Brumm said. The effect would probably have been weaker than that produced by a modern betel quid, but the experiment suggested that the ancient practice could still have delivered a psychoactive effect.

Their Teeth May Have Paid The Price

The same habit that may have delivered pain relief or a mild psychoactive effect also appears to have caused serious dental damage. Areca seeds are hard and abrasive, and repeatedly holding them in the mouth for hours could grind away enamel over many years.

“Over time, however, sucking these hard, abrasive seeds wore down the foragers’ teeth so badly that in some cases the inner pulp chamber became completely exposed,” Brumm said. The pulp chamber contains the sensitive inner tissue of a tooth, meaning this level of damage would have been extremely painful.

Researchers believe the practice may even have been connected to dental pain. Arecoline can produce a numbing sensation, while the repeated use of the abrasive seeds could worsen existing damage. Brumm suggested the individuals may have been using betel nut as a traditional remedy for toothache, creating a damaging cycle.

The researchers described that possibility as a vicious cycle: the substance may have provided relief while the physical practice continued destroying the teeth.

Two Ancient People Cannot Answer Every Question

The evidence is striking, but the researchers also acknowledge its limits. The conclusion is based on only two individuals, and human remains from this period are exceptionally rare in the region.

That means researchers cannot know exactly why these particular people used betel nut. Pain relief is one possible explanation, but it remains an interpretation rather than something that can be proven from the skeletons alone.

Several outside specialists have also urged caution. José Capriles of Penn State said he wanted to see additional evidence, including actual betel seeds preserved at ancient sites. Agustín Fuentes of Princeton has also cautioned against automatically applying modern ideas about pain and drug use to people living thousands of years ago.

Peter Ungar of the University of Arkansas viewed the combined evidence more strongly. “When you add the chemical evidence, that’s pretty much a smoking gun,” he said.

Brumm has acknowledged the uncertainty that comes with reconstructing behavior from such distant periods. “As always with archaeology, you’re dealing with vast unknowns.”

The Evidence Pushes Drug Use Back Into The Ice Age

The discovery could significantly extend the known history of psychoactive substance use. Earlier archaeological evidence had placed some ancient drug practices thousands of years later, while chemical evidence for betel nut itself had previously been identified in much younger human remains.

The Sulawesi evidence pushes the story back into the Ice Age. The grooves in the teeth, combined with the chemical detection of arecoline and the laboratory experiment, provide several independent clues pointing toward repeated betel nut use.

The researchers’ findings also suggest that humans were experimenting with plants for effects beyond basic nutrition long before farming transformed human societies.

Several clues in the evidence point toward repeated use:

• Deep dental grooves: The unusual wear appeared in consistent locations on the teeth.
• Chemical evidence: Arecoline was detected inside dental tissue from both individuals.
• Laboratory testing: Extracts from intact betel nuts interacted with human brain receptors.
• Long-term damage: The abrasive seeds appear to have caused severe dental wear over time.
• A 10,000-year gap: Two people from different periods showed remarkably similar evidence of the practice.

An Ancient Habit That Still Exists Today

Betel nut use did not disappear with the end of the Ice Age. The practice continued across generations and remains widespread in parts of South and Southeast Asia and the Pacific.

Modern medical research has also established serious risks associated with habitual areca nut use. The International Agency for Research on Cancer classifies areca nut as carcinogenic to humans, and regular use is strongly assforaociated with oral cancer.

That makes the ancient teeth more than an archaeological curiosity. They offer a glimpse at how long humans have experimented with substances that alter sensation, mood or perception, while also showing that the consequences of repeated use can stretch far beyond the immediate experience.

The researchers estimate that more than 600 million people use betel nut today. That means a practice apparently recorded in two Ice Age mouths may have survived for tens of thousands of years and remains part of daily life for a substantial global population.

The Teeth Preserved What People Could Not Tell Us

The two individuals left no written record of what they were thinking, why they used the nuts or how often they consumed them. Their teeth became the record instead.

Those grooves may represent one of the oldest physical traces yet found of people repeatedly using a psychoactive substance. They also show how much information can survive in the human body long after every other trace of a person’s daily routine has disappeared.

Twenty-five thousand years later, the damage in a set of teeth is still telling researchers something about what people put in their mouths, what they sought from it and what they were willing to endure for the effect.