Humans used betel nuts as drugs 25,000 years ago: Ancient teeth reveal the surprising psychoactive habit that began around the Ice Age

Humans may have been experimenting with mind-altering plants long before the first farmers settled down.

A new study of ancient remains from Sulawesi, Indonesia, suggests that hunter-gatherers were repeatedly using betel nuts as a psychoactive substance during the Ice Age. Researchers reached the conclusion by combining evidence preserved in human teeth with laboratory tests examining how the plant's active compound behaves.

The finding adds to growing evidence that prehistoric people had a sophisticated understanding of plants and their effects, even before agriculture transformed human societies.

Ancient teeth preserve clues to a forgotten practice

The strongest clues came from the teeth of two prehistoric individuals.

Researchers identified deep, rounded grooves that did not resemble normal patterns of wear. The damage indicated repeated contact with a hard object over an extended period.

The older individual lived between about 25,000 and 16,000 years ago, while the younger dates to approximately 7,600 to 6,300 years ago.

The researchers then looked for a chemical signature that could explain the unusual wear. Tests detected arecoline, the psychoactive compound naturally present in betel nuts, within the dental tissue.

The combination of the physical and chemical evidence points to repeated consumption rather than an isolated encounter with the plant.

The prehistoric method was different from modern betel use

The findings also suggest that these ancient people were not necessarily using betel in the same way it is traditionally consumed today.

Modern betel quid is generally prepared by combining areca nut with slaked lime and other ingredients. The lime helps increase the availability of the plant's active compounds.

The Sulawesi individuals appear instead to have sucked whole betel nuts.

To test whether that could have produced a psychoactive effect, scientists recreated the process using artificial saliva. They found that arecoline could be released from an intact nut at levels capable of interacting with receptors involved in nervous-system activity.

The effect would likely have been milder than that associated with prepared betel quid, but it could still have altered the user's brain activity.

A habit that may have begun with pain

There may have been more than one reason for the practice.

The researchers note that arecoline has pain-relieving properties. Since the ancient individuals also showed signs of serious dental problems, they propose that betel nuts could initially have been used to manage toothache.

Repeated use, however, appears to have created its own problems.

The abrasive seeds could progressively damage teeth, with severe wear eventually exposing the pulp. That would have increased the risk of infection and made eating difficult.

The researchers therefore suggest a possible cycle in which a substance used to relieve dental pain gradually contributed to further oral damage.

Evidence of drug use long before agriculture

The Sulawesi discovery is important because it moves the known history of habitual psychoactive substance use well into the Late Pleistocene.

Previously documented examples of ancient drug use are generally much younger. Fermented alcoholic drinks, for example, have been traced to around 13,000 years ago.

The new evidence indicates that people were repeatedly using a psychoactive plant more than 10,000 years earlier.

It also challenges the assumption that regular drug use emerged mainly after farming and permanent settlements became widespread.

Instead, psychoactive plants may have played a role in human behaviour while communities were still living as hunter-gatherers.

Why this discovery matters today

The study also highlights a major challenge for archaeologists trying to reconstruct ancient drug use.

Plant material is rarely preserved for tens of thousands of years. Seeds, leaves and other organic remains can disappear completely, leaving researchers with little direct evidence of what people consumed.

Teeth offer another route into the past.

Changes in dental structure can preserve evidence of repeated behaviour, while chemical traces can potentially reveal exposure to particular substances. The combination used in the Sulawesi study could therefore help researchers investigate whether other prehistoric communities had similar habits.

The researchers stress that 25,000 years ago should be viewed as the earliest evidence identified so far, rather than the definitive beginning of human drug use.

There could have been much older examples that left no surviving archaeological trace.

What the new study does establish is that habitual use of a psychoactive plant was already taking place during the Ice Age, revealing a side of prehistoric human behaviour that is rarely visible in the archaeological record.

FAQ about ancient human drug use

What drug did humans use 25,000 years ago?
Researchers found evidence that prehistoric hunter-gatherers in Sulawesi were repeatedly using betel nuts, the seeds of the Areca catechu palm, which contain the psychoactive compound arecoline.

How did scientists discover the ancient drug use?
They examined unusual patterns of tooth wear and detected arecoline in dental tissue. Together, these findings provided evidence of repeated betel nut consumption.

Why might ancient humans have used betel nuts?
Researchers believe the practice may have partly been linked to pain relief, as arecoline has analgesic properties. The psychoactive effects may also have been desirable.

Is this definitely the oldest drug use by humans?
It is currently considered the earliest known evidence of habitual drug use, but scientists cannot say that humans first began using psychoactive substances 25,000 years ago. Earlier examples may have existed but left no detectable archaeological evidence.