Teeth from two ancient foragers in Sulawesi carry an unusual combination of severe wear and chemical traces that points to a previously unrecognized way of using betel nuts: holding whole nuts in the mouth and repeatedly sucking them. The older individual lived between about 25,000 and 16,000 years ago, placing this form of betel-nut use deep in the Late Pleistocene, long before farming and thousands of years before the earliest securely dated evidence for conventional betel-quid use.
The evidence began with two sets of human remains from South Sulawesi, Indonesia.
The older individual, known as Maros-LBB-1a, was recovered from Late Pleistocene deposits at Leang Bulu Bettue. The remains are dated to roughly 25,000 to 16,000 years ago. The second individual, CPL-R2a, came from Leang Cappalombo 1, about 33 kilometers away, and dates to approximately 7,600 to 6,300 calibrated years ago.
Both were adult foragers, and both had an unusual form of dental damage that the researchers say has not previously been formally described.
Instead of the ordinary wear expected from chewing food, their teeth had pronounced circumferential wear. The surfaces around the teeth had been worn into rounded, hollowed-out grooves.
In Maros-LBB-1a, the three preserved molars showed severe circumferential wear. The third molar was considerably more worn than the second, suggesting that something hard and roughly spherical had repeatedly been held toward the back of the mouth. The researchers estimate that the object was about 10 to 20 millimeters across.
The second molar showed much less of the same wear. That difference led the researchers to propose that the object had not stayed in one place. It appears to have been moved around the mouth repeatedly.
CPL-R2a had an even more extensive pattern. Circumferential wear affected both upper and lower molars, as well as premolars and canines. Some of the wear was severe enough to expose tooth roots. The pattern also extended to the front teeth, suggesting that the object had been held in different parts of the mouth.
The wear resembles the rounded notches known from dental damage caused by habitual clay-pipe smoking, although the researchers were not suggesting that these ancient foragers smoked pipes. Instead, that comparison helped them interpret the physical action that could have produced the unusual grooves.
The simplest explanation was that the individuals had repeatedly held a hard, round object between their teeth and sucked or gently gnawed it.
The object was probably a whole areca nut
The dimensions of the wear offered another clue.
The researchers found that the size was consistent with smaller whole, dehusked areca nuts, including Areca triandra, a wild areca palm native to Sulawesi.
That led them to propose a very different behavior from the familiar betel quid used in many parts of Asia and the Pacific today.
Rather than cutting the nut into pieces and chewing it with slaked lime and betel leaf, these foragers may have removed the husk and kept an intact nut in their mouths. They apparently held it between their teeth while moving it around with their tongue and mouth muscles, and possibly gently gnawed it for prolonged periods.
The researchers use “sucking” for both of these actions.
The behavior would not have been a way of obtaining food. The authors note that an areca seed has no nutritional value, making nutrition an unlikely explanation for such persistent manipulation of the nut.
There was another important clue. Neither individual’s teeth showed the characteristic discoloration expected from betel-quid chewing.
That matters because conventional betel quid contains slaked lime. The alkaline mixture produces a distinctive red colorant that can eventually leave a reddish-brown stain on the teeth. Although both ancient individuals had some staining associated with age and burial processes, the researchers found no discoloration consistent with betel-quid chewing.
They therefore ruled out conventional betel-quid use as the cause of the unusual dental pathology.
The question became whether an intact nut could nevertheless deliver the psychoactive chemistry associated with areca.
An intact nut can release arecoline
Modern betel use usually involves a prepared quid containing areca seed, slaked lime and betel vine leaf. Arecoline, an alkaloid in the areca nut, is considered the principal neuroactive compound.
The researchers tested whether a whole nut, without being cut up or mixed with lime, could release arecoline.
They examined three types of areca nut: dried Areca catechu nuts commonly known as supari, fresh A. catechu nuts from Vietnam, and the wild species A. triandra.
Some nuts were left intact. Others were broken or sliced. The researchers then incubated them in a saline solution under conditions intended to approximate prolonged exposure in the mouth.
The solutions from the intact nuts contained compounds capable of activating human M1 and M3 muscarinic acetylcholine receptors. The intact dried A. catechu nuts produced particularly strong transient receptor responses.
The researchers also tested whether other components of the nut were released. Solutions from intact nuts produced no detectable response in cells carrying human GABA type A receptors, suggesting that GABA and the high-molecular-weight components tested were not released in the same way.
Taken together, the experiments indicated that keeping an intact areca nut in the mouth could release arecoline in amounts sufficient to produce physiological effects associated with betel-nut ingestion, including excessive salivation.
The result provided a plausible chemical basis for the ancient behavior inferred from the teeth.
It also meant that a person did not necessarily need to know how to prepare a conventional betel quid to obtain a physiological effect from an areca nut.
Ancient teeth preserve the chemical evidence
The researchers then looked directly for chemical traces in the ancient teeth.
They used liquid chromatography–mass spectrometry, or LC-MS, to analyze residues from teeth belonging to both individuals. Unlike several earlier approaches used to recover ancient biomolecules, this study did not cut, grind or acid-etch the teeth. Instead, the samples were soaked in solvents to extract compounds from residues on and within the dental tissues.
The intact molar from Maros-LBB-1a tested positive for arecoline.
That provides direct chemical evidence that this Late Pleistocene individual had consumed betel nut.
The researchers also detected several compounds associated with betel vine leaf, including eugenol, eucalyptol, cumene and citral. Other compounds associated with the leaf were detected in one of the samples.
But the presence of these chemicals does not establish that the individual was making a conventional betel quid. The researchers note that Piper betle leaves contain aromatic compounds and could have been consumed separately as flavorings or for medicinal purposes.
The chemical evidence from CPL-R2a pointed in the same general direction. Two tooth samples contained compounds found in A. catechu, but only the intact tooth bearing the distinctive circumferential wear contained detectable arecoline.
That individual therefore also had chemical evidence of betel-nut ingestion.
Several other betel-related compounds, including guvacine, guvacoline and arecaidine, were not detected. The researchers point out that guvacine and arecaidine occur naturally in very small amounts in betel nuts but are produced in much larger quantities when slaked lime is used in a betel quid.
The combination of detectable arecoline, the absence of clear betel staining and the lack of those compounds is consistent with the individuals having consumed areca without slaked lime.
Together with the unusual tooth wear, the evidence supports the researchers’ hypothesis that the nuts were being held and sucked whole.
The habit came with severe dental damage
The chemical evidence helps explain why someone might repeatedly hold a hard nut in the mouth for years. But the teeth also show the cost of doing so.
Both individuals had poor oral health. Maros-LBB-1a had periodontal disease affecting the preserved teeth. CPL-R2a had extensive periodontal disease and other dental problems.
In CPL-R2a, the wear was particularly severe. The repeated activity had worn the teeth deeply enough to expose pulp cavities in several places, leading to chronic infection.
The researchers argue that such deep wear could not have developed from a brief or occasional behavior. The individuals must have continued the activity for many years.
That persistence is one reason the authors interpret the behavior as potentially related to dependence on the chemical effects of areca rather than simply an incidental habit.
But they stop short of treating the motivation as established.
The psychoactive properties of areca seeds are one possibility. The authors also propose that the practice could have had a medicinal purpose. Arecoline stimulates salivation, and the researchers suggest that the resulting increase in amylase production could have helped with the digestion of starchy foods such as wild sago.
They also raise another possibility based on the known analgesic properties of arecoline. Because CPL-R2a suffered from severe periodontal disease, the researchers suspect that the individual may have used areca seeds as a form of pain relief.
That interpretation remains a hypothesis. The evidence cannot reveal directly why either individual used the nuts.
The researchers instead suggest a possible cycle in which sucking areca seeds for tooth pain could have become an increasingly strong habit as the resulting dental damage worsened.
The older evidence changes the timeline
Before these findings, the earliest securely dated and relatively unambiguous evidence for betel-nut consumption consisted of chemical traces of arecoline in dental calculus from an individual in Bronze Age Thailand, dating to roughly 3,500 to 3,000 years ago.
The Sulawesi evidence is substantially older.
Maros-LBB-1a dates to about 25,000 to 16,000 years ago. The researchers therefore place habitual areca-nut sucking among Sulawesi foragers in the Late Pleistocene, long before the emergence of agriculture.
That does not mean the modern betel quid existed at the same time.
The authors distinguish the newly proposed practice from the later custom of preparing a quid with processed areca, slaked lime and betel leaf. When and where that more elaborate practice began remains unknown.
They propose that betel-quid use may have developed from the simpler practice of sucking an intact nut. One possibility they raise is that Neolithic farmers later introduced slaked lime to Sulawesi, potentially allowing a prepared quid tradition to emerge after the arrival of Austronesian-speaking groups roughly 4,000 years ago.
That sequence is still a possibility rather than an established history.
The evidence from the two ancient individuals is also necessarily limited. The study concerns only two people, and skeletal remains from preagricultural Sulawesi are rare. Their advanced ages make them especially likely to preserve evidence of long-term tooth-use habits, but the small sample cannot establish how widespread the behavior was among other ancient foragers.
What the teeth do provide is a rare physical record of a behavior that normally would leave little archaeological trace.
A hard seed repeatedly held in the mouth can disappear without leaving obvious remains at an archaeological site. The damage it causes to teeth, however, can persist for thousands of years. In these two Sulawesi individuals, that dental record is reinforced by chemical traces of areca and by experiments showing that an intact nut can release arecoline.
The result is evidence for an early form of betel-nut use in which people appear to have held whole nuts in their mouths for prolonged periods, centuries before the prepared betel quid became part of the archaeological record.
The study was published in Science Advances.
