Two teeth, deep and rounded grooves, a molecule trapped in the tooth tissues for thousands of years. This is where what could be comes from the oldest known evidence of habitual use of a psychoactive substance: Two hunter-gatherers who lived on the Indonesian island of Sulawesi sucked betel nuts, one of which dates back to between 25,000 and 16,000 years ago.
The discovery comes from a study published in Science Advances by an international team led by archaeologist Adam Brumm of Griffith University. The second individual analyzed is much more recent, living between 7,600 and 6,300 years ago. Only two people, therefore, both from Sulawesi: enough to push the known chronology back quite a bit, too few to already imagine a widespread habit among all human groups of the time.
Those grooves on the teeth were too strange to be simple wear
The researchers started with a detail that was difficult to ignore. Both individuals presented on the teeth deep and rounded groovesdifferent from the flatter wear caused by normal chewing. In the oldest case, the remains come from the site of Leang Bulu Bettue, in South Sulawesi, and belonged to a man who died probably between 40 and 50 years old.
The proposed explanation is quite concrete: those teeth would have held the whole seeds of the palm for a long time and repeatedly Areca catechuthe so-called betel nuts. Today they are normally crushed and consumed together with other ingredients, especially slaked lime, which facilitates the release and absorption of arecoline, the alkaloid responsible for the stimulating effects.
The hunter-gatherers of Sulawesi appear to have done something much simpler: they held the whole nut in their mouths and sucked it. No elaborate preparations, no agriculture, not even a convenient ready-to-use sachet. Yet the effect could have arrived anyway.
To test this, the team immersed betel nuts in artificial saliva and then tested the solution on human receptors cloned and expressed in frog oocytes. The result showed that simply prolonged contact with saliva can release arecoline in quantities sufficient to produce a physiological effect. Biomolecular analysis then made the hypothesis much more robust: traces of the same substance were identified in the dental tissues of the individuals studied.
Maybe it also helped against toothache. With rather questionable results
Why they did this is more difficult to establish. Arecoline has stimulant effects and can cause mild euphoria and increased alertness, but the authors also put forward another possibility: Walnuts could be used to ease tooth pain.
In fact, ancient human remains from Sulawesi show dental conditions that are far from impeccable and arecoline has analgesic properties. Furthermore, betel nut offers little from a nutritional point of view: keeping it in the mouth for a long time would have made little sense as a simple food.
The remedy, if it were, however, presented a notable drawback. Years of contact with those hard and abrasive seeds wore down the teeth until, in some cases, to the exposure of the pulp chamber. Pain, difficulty eating and increased risk of chronic infections. A solution for toothache capable of producing more toothache: some human habits seem to have really deep roots.
The use of psychoactive substances may predate agriculture by thousands of years
Dating is the part that makes the study particularly interesting. Until now, much of the strongest archaeological evidence for the use of psychoactive substances belonged to periods after or close to the birth of agriculture. Among the oldest examples, the production of a fermented drink in the Levant about 13 thousand years ago is often cited.
The Sulawesi hunter-gatherer brings the behavior instead up to the Upper Paleolithic, between 25 thousand and 16 thousand years ago. The authors then talk about the possible oldest known evidence of the habitual use of a neuroactive herbal drug. The conditional has weight: the record concerns the evidence found so far, and the sample includes just two individuals.
However, the discovery changes an interesting part of the story. The repeated use of plants capable of modifying perception, attention or pain may have arisen long before agricultural villages, organized alcohol production and sedentary societies. At least in Sulawesi, someone had already discovered that a plant could do more than fill the stomach. And the teeth, after thousands of years, have retained both the habit and the bill to pay.
