Stone Age high: Ancient Indonesian foragers may have sucked on mind-altering nuts 25,000 years ago, study finds

What may be the earliest known evidence of human drug use has been traced to ancient foragers on the Indonesian island of Sulawesi, who appear to have sucked on mind-altering betel nuts as far back as 25,000 years ago, according to a study published in the journal Science Advances.

Analysis of two exceptionally rare prehistoric skeletons revealed dramatic tooth wear alongside chemical traces of a psychoactive compound in the individuals' remaining teeth, suggesting they routinely held and sucked on hard, abrasive betel nuts long before humans are thought to have taken up any form of drug use.

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Betel nuts remain the world's fourth most widely used psychoactive substance today, after alcohol, caffeine and nicotine, with an estimated one in ten people worldwide still chewing the seeds.

Grooves that stumped the researchers

The study's lead author, archaeologist Adam Brumm of Griffith University's Australian Research Centre for Human Evolution in Brisbane, said the discovery sheds light on how one of the region's most enduring drug habits may have originated.

"We've found evidence for how this very common drug use habit, which is found throughout a lot of the Asia-Pacific region today, might have evolved," Brumm said.

The research began with the examination of two pre-agricultural foragers' remains, unearthed at two separate sites on Sulawesi. The older specimen, a jawbone fragment catalogued as Maros-LBB-1a, came from Leang Bulu Bettue, a limestone cave in South Sulawesi's Maros-Pangkep karst landscape, and dates to between 25,000 and 16,000 years ago, making it the only Pleistocene-era human skeletal remain ever recovered on the island.

The second, younger set of remains, found at a different cave roughly 20.5 miles away, dates to about 7,000 years old.

Both individuals had deep, rounded grooves worn into their teeth, some deep enough to have exposed the dental pulp. "I was thinking, what the hell were these people doing? It's like someone had a drill head shaped like a gobstopper and wore away the inner part of the tooth," Brumm said.

Testing the betel nut theory

Betel nuts are technically the seeds of the Areca catechu palm, commonly mislabelled because they are typically wrapped in betel vine leaves for chewing. Today they are usually mixed with slaked lime, made from ground burnt shells, to form a "quid" that intensifies their psychoactive effect. Brumm's team suspected the ancient foragers had been sucking on the whole, unprocessed nuts before this quid-making method was discovered.

To test the theory, researchers soaked betel nuts in artificial saliva and found it quickly contained enough arecoline, the nut's active psychoactive compound, to produce a mild high, less potent than that from chewing a prepared quid. Chemical analysis of the ancient teeth turned up traces of arecoline consistent with this. "I've sucked on a nut as an experiment and it's a really bitter, astringent taste. It makes your mouth go numb and I think that's what they were interested in," Brumm said.

A self-perpetuating cycle of pain

Brumm suggested the habit may have begun as an attempt at pain relief. "This might have been a traditional remedy for toothache, but if they did it for too long, sucking on the nut wore down their teeth so badly that it actually created much worse dental pain in the long term," he said. "These individuals were seemingly caught in a self-perpetuating cycle where they were continually sucking on the nuts to treat the tooth pain caused by this nut-sucking habit."

Researchers believe the practice may have evolved into the more familiar betel-chewing tradition around 4,000 years ago, when Austronesian farming communities expanding out of Taiwan settled in Sulawesi and began mixing the nuts with slaked lime for a stronger effect.

Until now, the earliest solid chemical evidence for betel nut use came from a Bronze Age site in Thailand dated to around 3,500 years ago, making the Sulawesi findings push the timeline back by roughly 12,000 years.

How does this compare to other ancient drug use?

While humans likely experimented with mind-altering plants as soon as they encountered them, the oldest known traditions of psychoactive substance use had previously been dated to around 13,000 years ago, tied to fermented drinks such as barley beer developed alongside early agriculture.

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Elisa Guerra-Doce, an associate professor of European prehistory at the University of Valladolid in Spain who was not involved in the study, said the findings offered "direct evidence of the antiquity of human drug use."

She added: "These findings not only represent the earliest known evidence to date of the use of psychoactive plants anywhere in the world, but also demonstrate that the consumption of Areca nuts is a millennia-old tradition dating back to prehistoric times."