Deep inside two limestone caves in South Sulawesi, about 33 kilometers apart, lie traces of two people who lived thousands of years apart. In Leang Bulu Bettue Cave, a jaw and teeth belonged to someone who lived between 25,000 and 16,000 years ago. The remains are among the oldest ancient human remains ever found in Sulawesi.
In Leang Cappolombo Cave, similar remains belonged to someone who lived much later. This individual lived between 7,600 and 6,300 years ago.
The two people never met. Thousands of generations separated their lives. Yet their molars preserve strikingly similar traces.
Both have deep, rounded cavities worn into their teeth. The shape suggests that something hard and round was repeatedly held between their teeth over many years.
The pattern does not resemble any form of prehistoric tooth wear documented before. For years, its cause remained a mystery.
Now, a team of archaeologists and biochemists from Griffith University, Hasanuddin University in Makassar, and the National Research and Innovation Agency (BRIN) has an answer. In a study published in Science Advances on September 11, 2026, the researchers concluded that both individuals had a habit of sucking areca nuts.
If the conclusion is correct, the practice is far older than any previously known evidence of areca nut consumption. Both individuals also lived as hunter-gatherers before farming emerged in their region.
The study describes them as preagricultural foragers. The finding provides the oldest known evidence so far of routine psychoactive substance use by humans.
A Mystery in the Molars
The first clue came from the shape of the damage. Adam Brumm, an archaeologist at Griffith University who led the study, compared the cavities in the two individuals’ teeth with something much more recent.
These marks are known as clay pipe facets. They have been found on the teeth of colonial-era smokers. The marks formed from repeatedly holding hard-stemmed clay pipes between the teeth over many years.
The shape reminded Brumm of another possibility.
“I immediately thought, it was probably betel nut,” he said.
The idea made physical sense. Areca nuts are the fruit of Areca palms that grow wild in Sulawesi. They are round and measure about one to two centimeters across.
If repeatedly held in the same spot between the molars, the hard nut could leave a distinctive pattern of wear.
In one individual, the damage had even penetrated the pulp cavity. This is the inner part of the tooth that contains the nerves. Such a condition would normally be very painful.
But the shape alone was not enough to determine what had happened thousands of years ago. The team then looked for clues that had remained in the fossilized tooth tissue.
They found arecoline. It is the main psychoactive compound found in areca nuts. Another question remained. Could arecoline be released simply by sucking on an unprocessed areca nut?
Previous research had suggested that the compound was mainly released when areca nut was chewed. In many places today, the nut is processed with slaked lime as part of traditional betel quid consumption.
To test the idea, the team soaked whole areca nuts in artificial saliva. They then tested the extract on frog eggs genetically engineered to express human brain receptors. The results showed that processing was not always necessary.
Holding and sucking a whole areca nut in the mouth for a prolonged period was enough to release arecoline. The amount was sufficient to trigger its effects. The traces in the teeth and the chemical evidence pointed to the same habit.
When Pain Relief Damaged the Teeth
There may be a simple reason why the habit began in the first place: pain. Both individuals had a history of poor dental health. Arecoline, meanwhile, is known to have pain-relieving effects.
Brumm suspects that this may have been why they first began sucking on areca nuts.
“I suspect that was the effect they were seeking,” he said.
But the habit came with a hidden problem. Areca nuts are hard and abrasive. The more often they were sucked, the more friction the teeth were exposed to.
A habit that may have begun as a way to ease toothache could therefore have gradually worsened the same dental damage.
“The more they sucked on the betel nut to relieve the pain, the worse the damage to their teeth became,” Brumm said.
For two people living thousands of years ago, a wild fruit may have been an available remedy when their teeth hurt. But repeated use left traces that lasted far longer than the pain they were trying to relieve.
An Areca Habit Older Than Farming
The Sulawesi findings also push back the history of areca nut consumption. Previously, the oldest evidence of areca nut consumption dated to the Neolithic period through the Bronze Age. The evidence was around 3,500 years old.
The individual from Leang Bulu Bettue pushes that record back by more than 20,000 years. What makes the finding even more striking is that both individuals lived before farming emerged in their region.
Agriculture emerged at different times across the world. The earliest evidence comes from the Fertile Crescent in the Middle East, around 10,000 to 12,000 years ago.
Similar processes developed at different times in New Guinea, southern China, and elsewhere. The individual from Leang Bulu Bettue lived long before these periods.
This means that the practice of consuming areca nuts did not have to wait for farming societies to emerge. It also did not require cultivated plants or a settled food system.
At least in Sulawesi, hunter-gatherers had already found a way to make use of a fruit growing in their surroundings as part of everyday life. Traces of the practice can still be found among people today.
According to the study, areca nut consumption today involves roughly one in 10 people worldwide. That amounts to around 800 million people out of a global population of about 8.1 billion.
The practice is especially common in South and Southeast Asia. Areca nuts are typically consumed as part of a quid that combines the nut with betel leaf and lime.
The way the two people in Sulawesi consumed it appears to have been much simpler. They did not mix it with anything else. They simply held and sucked the whole nut in their mouths.
Today, long-term areca nut consumption is associated with reddish staining of the teeth. It is also linked to an increased risk of oral cancer and cardiovascular disease.
