A team of researchers working in Indonesia has uncovered ancient teeth bearing unusual grooves, and they believe they have identified the cause: a long-standing habit among hunter-gatherers of sucking on betel nuts for decades. The findings, detailed in Science Advances, indicate the practice stretches back at least 25,000 years.
Two sets of teeth from the island of Sulawesi, now part of modern-day Indonesia, were at the center of the discovery. One set was traced to a person who lived roughly 25,000 years ago. The second set, recovered about 20 miles to the east, came from a person who lived up to 8,000 years ago. What puzzled the researchers were the deep, round marks found on both sets.
| Tooth Set | Age | Location |
|---|---|---|
| First set | Roughly 25,000 years ago | Island of Sulawesi |
| Second set | Up to 8,000 years ago | Recovered about 20 miles to the east |
“There were really strange grooves in the teeth that we couldn’t explain,” says Adam Brumm, a professor of archaeology at Griffith University in Australia who led the research.
Grooves That Wouldn’t Explain Themselves
An archaeological expedition on Sulawesi uncovered the remains that Brumm and his colleagues examined. The teeth bore marks that were unfamiliar to the researchers. The grooves were neither from chewing nor from using teeth as tools, a practice that hunter-gatherers were known to engage in.
Every ordinary explanation was dismissed by the group. The markings could not be attributed to food. They did not come from plant fibers processed into string. None of the typical applications of teeth matched the forms of the grooves.
Several teeth in the older set had marks so deep that they exposed the nerve center, which Brumm described as a pattern that likely took decades of repeated wear to form.
The Pipe-Smoking Clue
Brumm recalled a similar instance of distinctive tooth wear during the colonial period in Europe, America and Australia. Laborers there habitually smoked tobacco from clay pipes, “They would have the pipe sticking out of their mouth, Popeye-style,” he explains. The habit left its mark over a lifetime: perfectly round notches in their teeth that matched the shape of the pipe stem.
Brumm and his team believed the tooth marks found in Indonesia came from a shared custom. They suspected the habit had its roots in cultural practices, but they needed evidence to support their idea.
Sucking the Betel Nut
Across Asia and the Pacific today, people chew betel nuts mixed with other chemicals to get a stimulant effect from the combination. The marks on the old teeth, however, show a habit more like sucking than chewing: wearing down from years of holding hard, round objects in the mouth.
The researchers believe they have found an initial phase in how the habit develops. As Brumm puts it, “We think they were hooked on nut-sucking,” the practice’s earliest form. Given that sucking betel nuts is rare nowadays, he joined forces with Professor Roger Papke, a neuropharmacological researcher at the University of Florida, to determine if the act produces a drug response.
“We soaked whole betel nuts in artificial saliva, and then introduced the resultant extracts into frog egg cells engineered to produce human brain receptors,” Brumm says. They found that the artificial saliva successfully extracted arecoline, an active chemical in the betel nut, and that the brain receptors turned on when they touched the saliva.
He says “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,”.
Proof in the Teeth
The team established that these ancient people actually sucked the nuts through two separate tests. They first matched the shape of the betel nuts to the grooves in the teeth. Then, they tested the dental tissues and discovered traces of arecoline — a substance for which betel nuts are the only known natural source, according to Papke.
Brumm also put himself in the mindset of ancient humans and tried sucking on betel nuts himself. “I had to give it a go,” he says. “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 believes that the numbing, pain-relieving effect was the goal for ancient hunter-gatherers. He suggests 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 says.
Human Nature and Drug Use
Experts observe that people have turned to mind-altering substances for centuries. This drive to push the limits of consciousness through chemical means is a fundamental aspect of being human, according to José Capriles, an associate professor of anthropology at Penn State University. He has discovered evidence of drug use among ancient South Americans dating back a thousand years.
The new study pushes back the timeline for substance use, reaching back to hunter-gatherers who lived tens of thousands of years ago. Capriles’s work already documents a lengthy history of such behavior.
A Long History of Substances
Betel nuts are considered the world’s fourth most commonly used mind-affecting substance, after tobacco, alcohol and caffeine. About 600 million people today chew on them — the brownish green seeds of certain palm trees that are about the size of a walnut. Users say they get relief from indigestion, fresh breath, and an energy boost.
Betel nuts carry chemicals that can hurt teeth, raise the risk of heart disease, and cause cancer of the mouth, according to the medical community. Even so, a large number of people across Asia and the Asian Pacific remain hooked on chewing them.
What the Teeth Tell Us
The teeth found on Sulawesi provide a rare look at ancient habits. Much archaeological proof comes from things that hint at past activity rather than showing it directly — pots, tools, bones. These teeth reveal a repeated act carried out across many years.
Both sets of teeth show marks that point to a habit involving repeated action over a long period. The wear patterns match up across the two sets, pointing toward sustained, habitual use.
The Cycle of Addiction
Brumm proposes that the numbing sensation attracted users, with the harm pushing them further into the habit. The teeth wore down to the nerve, setting off more sucking that briefly eased the discomfort even as it caused worse injury.
What Comes Next
Researchers are asking whether the practice began in a single location and then moved outward from there, or whether it developed separately in different places over time.
To understand the complete history of the practice, researchers will need to examine additional sites and ancient populations beyond those already studied.
The teeth from Sulawesi currently serve as evidence that humans have been testing plants for a very long time. The urge to sample new substances is part of our nature, and these teeth demonstrate it directly — through the grooves themselves.
A strong argument is made here for the long history of betel nut use. The teeth hold the evidence, and the scientists have worked hard to interpret what they reveal.
Source material: “Ancient teeth pose a mystery: What made those strange grooves?,” NPR.
Get the Notebook.
The day's best stories and every fresh verdict, in plain English, in your inbox by seven. One email a day, no more.