Long before humans were brewing beer or planting crops, people on the Indonesian island of Sulawesi may already have been regularly using a psychoactive plant.
New evidence from ancient teeth suggests that practice began as far back as 25,000 years ago.
Here's what to know
Earth.com said researchers linked unusual dental grooves in two ancient Sulawesi skeletons to repeated betel nut use, involving the seed of the areca palm. The study appeared in Science Advances.
If correct, the find pushes regular drug use much further into the past. Many archaeologists had tied sustained psychoactive consumption to farming, yet the earliest secure evidence for brewed alcohol is only about 13,000 years old from Israel, and betel nut itself had previously been verified in teeth from around 4,000 years ago, nearer the regional rise of agriculture.
Adam Brumm, an archaeologist at Griffith University's Australian Research Centre for Human Evolution, said that assumption may have missed another possibility.
"However, this theory fails to account for the possibility that very ancient drug-taking lies at the roots of our most commonly used psychoactive substances," he said, per Earth.com.
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The researchers were working with two especially uncommon skeletons. One, from Leang Bulu Bettue, is dated to roughly 25,000 to 16,000 years ago. The other belonged to someone who lived about 7,600 to 6,300 years ago. In both mouths, the team identified the same deep, rounded tooth wear, which they said was unlike either normal cavities or the flatter damage left by hard-to-chew foods.
More background
Betel nut use is still common: about one in 10 people worldwide chew it, particularly in South and Southeast Asia and across the Pacific. A typical modern preparation is a quid that combines the nut with slaked lime produced by burning and grinding shells.
"Slaked lime is an essential ingredient because it causes a chemical reaction that releases the nut's psychoactive compounds into the bloodstream more rapidly," Brumm said.
But the ancient Sulawesi teeth lacked signs of that prepared mixture approach.
That led the team to propose a different habit among these hunter-gatherers: slowly sucking whole nuts without processing them first. They tested the idea by soaking betel nuts in artificial saliva, then exposing human arecoline receptors grown in frog egg cells to the resulting liquid.
"This showed that just sucking on intact betel nuts will release arecoline in sufficient amounts to have a physiological effect, altering brain function," Brumm said.
Since betel nut provides little nourishment, the researchers argued its appeal may have included pain relief, especially because the island's ancient foragers seem to have suffered from poor dental health.
At the same time, repeated use may have contributed to further oral damage by wearing teeth down and exposing the sensitive pulp.
What's being done?
More broadly, the project reflects an increasing push to pair archaeological evidence with chemistry and lab experiments when skeletal remains alone cannot answer a question.
Researchers from Hasanuddin University in Makassar and Indonesia's National Research and Innovation Agency worked alongside Brumm's group on the study. In a separate test, ARCHE biochemist Carney Matheson also identified arecoline within the ancient teeth through chemical analysis.
Similar tooth wear and matching chemical residue from other ancient sites in Asia and the Pacific would strengthen the case.
"Emerging by up to 25,000 years ago in Sulawesi, thus long preceding the onset of agriculture, betel nut-sucking may be the earliest evidence for drug use anywhere in the world," Brumm said.
Where can I learn more?
For more on ancient disease, cave discoveries, and early tools, check out these stories.
• In Siberia, ancient teeth show plague struck hunter-gatherers long before cities emerged.
• At a cave in Türkiye, matching shells and symbols linked Neanderthals with modern humans.
• Deep in South Africa's Wonderwerk Cave, scorched bones suggest humans managed fire nearly 1.8 million years ago.
• At an ancient lake bed, the oldest wooden tools reshaped ideas about early humans.
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