Outside researchers call combined evidence a ‘smoking gun’ while urging caution
The remains came to light on an archaeological dig in Sulawesi, an island in modern-day Indonesia. Archaeologist Adam Brumm of Griffith University in Australia and his colleagues excavated the skeleton of a hunter-gatherer who lived as far back as 25,000 years. The teeth carried deep grooves that no expert in ancient dental wear contacted by the team could initially explain. “There were really strange grooves in the teeth that we couldn’t explain,” Brumm said.
He emailed “all of the world’s leading experts in ancient dental wear” for advice. “None of them could explain how these grooves could have formed,” Brumm said. About 20 miles to the east, the team found a second set of teeth from a human who lived up to 8,000 years ago, with similar marks.
“The grooves were so deep that they had actually exposed the pulp cavity, the nerve center, of several teeth,” Brumm said, describing a pattern that likely took decades of repeated wear to form. While hunter-gatherers from that time are known to have used their teeth as tools — holding, breaking, stretching things — none of those uses matched the grooves. “We ruled out any type of food they might have been eating, we ruled out the possibility that they were processing plant fibers to make string in their mouth,” Brumm said.
Brumm recalled a parallel from the colonial period in Europe, America, and Australia, where laborers habitually smoked tobacco from clay pipes. “They would have the pipe sticking out of their mouth, Popeye-style,” Brumm explained. “Over a lifetime of this habit, they’ve got a perfectly round notch in their teeth that you can slot the clay pipe stem straight into.” The shape of the Sulawesi grooves suggested something similar — long-term contact with a hard, round object held in the mouth. Betel nuts, about the size of a walnut, fit the bill.
The wear patterns on the teeth were consistent with sucking — not chewing — hard, round, abrasive objects over many years, Brumm said. “We think they were hooked on nut-sucking,” he said. “We think it might have started with hunter-gatherers just sucking on the nuts, almost as though they were gobstoppers.” “It’s a chance archaeological discovery that reveals an initial stage in the development of this common drug used today,” Brumm said.
To test whether sucking — rather than chewing — could have produced the pattern, Brumm partnered with Roger Papke, a neuropharmacological researcher at the University of Florida. They soaked whole betel nuts in artificial saliva and introduced the extracts into frog egg cells engineered to produce human brain receptors. The saliva successfully extracted arecoline, an active chemical in the betel nut, and the brain receptors turned on when they touched the saliva. “We’ve shown that if you just suck on the nut, there’s a physiological reaction that can be released into your bloodstream and then into your brain, and that can alter human brain function,” Brumm said.
The team also tested the dental tissues of the ancient remains and found traces of arecoline — for which betel nuts are the only known natural source, Papke said. To further test the hypothesis, Brumm put himself in the mindset of ancient humans and tried sucking on betel nuts himself. “I had to give it a go,” he said. “If you gently gnaw on the outside of it, it releases the betel juice. It has this extremely bitter and astringent taste that makes your whole mouth go numb.”
Brumm hypothesizes that the numbing, pain-relieving effect was what ancient hunter-gatherers were after, and that the betel nut suckers eventually wore their teeth down to the nerve — which he says could have been very painful — leading to more nut-sucking to relieve the pain. “They were essentially caught in this cycle and they were basically addicted to this natural plant drug,” Brumm said.
Outside researchers said the paper makes a compelling case for ancient betel nut use. “There’s evidence for the betel nut causing excessive tooth wear. When you add the chemical evidence, that’s pretty much a smoking gun,” said Peter Ungar, a distinguished professor of anthropology at the University of Arkansas who studies teeth and was not involved in the study. Agustín Fuentes, a professor of anthropology at Princeton University, said the finding “fits with the bigger picture of our understanding of betel [nut] use and also the cultural dynamics of that time period.”
Others wanted additional support. “I wish there was more, I must admit — there are two skeletons that they report,” said José Capriles, an associate professor of anthropology at Penn State University who has documented ancient drug use in other contexts, including drugs used by humans a thousand years ago in South America. Capriles acknowledged that well-preserved ancient human remains are difficult to find, especially in tropical areas where heat and humidity break them down. Still, “more direct evidence would be the actual finding of the nuts, of the seeds, ideally in some form of cultural context,” such as a hearth, house floor, or burial site, he said.
Archaeologists not involved with the study were wary of making assumptions about why ancient people were attracted to betel nuts. “We have to be very, very careful not to associate our particular assumptions of pain or patterns,” Fuentes said. “I think they’re using a contemporary public health and dentistry approach to think about very complicated cultures of the past.” There might have been other social and cultural reasons for the teeth-damaging practice, Fuentes noted. After all, people today eat hard candy, open bottles with their teeth, and neglect to brush and floss. “All of these things are not directly good for your teeth, but they serve other social [purposes] in other kinds of contexts,” he said.
“The instinct to experiment and expand our horizons with substances is part of human nature,” Capriles said.
Brumm acknowledged the limitations of the work. “As always with archaeology, you’re dealing with vast unknowns,” he said. “But we’ve put a lot of thought into this, and we think this is what was going on.”
Today, about 600 million people chew on betel nuts — the brownish green seeds of certain palm trees that are about the size of a walnut — across Asia and the Pacific, where they are commonly chewed with other chemicals for their combined stimulant effects. Users say they get relief from indigestion, fresh breath, and an energy boost. Many people in the region are addicted to chewing them. Medical research has linked long-term use to dental damage, increased risk of heart disease, and oral cancers associated with the chemicals in the nut. Betel nuts rank as the world’s fourth most commonly used mind-affecting substance, after tobacco, alcohol, and caffeine.