People got high on mind-bending drugs much earlier than initially believed

The findings suggest that our ancestors were using psychoactive substances 25,000 years ago — before agriculture even began.

Archaeologists have uncovered evidence in Indonesia that humans were using mind-altering substances much earlier in time than previously supposed.

They suspect early hunter-gatherers sucked on nuts to ease toothache.

Researchers combined biochemical and archaeological evidence to trace the prehistoric roots of one of the world's most popular addictive stimulants.

Betel nut is a drug used throughout much of the Asia-Pacific region today.

The study, published in the journal Science Advances, shows that the use of betel nut as a drug emerged among some Indonesian communities up to 25,000 years ago.

That is over 20,000 years before any previous evidence of drug use found anywhere else in the world.

It was previously understood that the first traditions of psychoactive drug use arose after the Neolithic advent of farming, beginning with the innovation of fermented alcoholic drinks about 13,000 years ago in Israel.

But study leader Adam Brumm said: "This theory fails to account for the possibility that very ancient drug-taking lies at the roots of our most commonly used psychoactive substances."

Brumm and his colleagues from the Australian Research Centre for Human Evolution (ARCHE) at Griffith University worked with Indonesian archaeologists from Makassar's University of Hasanuddin and the National Research and Innovation Agency (BRIN).

Their investigation focused on the origins of betel nut use, a tradition maintained by hundreds of millions of people in India and the South Pacific today.

Chewing betel nut induces a sense of mild euphoria and heightened alertness, among other effects.

Brumm said: "Although poorly known in western societies, it is the world's fourth most widely used psychoactive substance, after alcohol, caffeine and nicotine."

Users today take the betel drug by mixing a processed seed of the Areca catechu palm — the betel "nut" — with slaked lime — commonly made by grinding burnt shells into a fine powder — and other ingredients to form a "quid" which is then chewed to get high.

Brumm said: "Slaked lime is an essential ingredient because it causes a chemical reaction that releases the nut's psychoactive compounds into the bloodstream more rapidly."

But the early history of betel use had remained uncertain, mainly because areca seeds were rarely preserved at archaeological sites.

The Griffith-led team discovered extremely rare skeletal remains of two early human foragers from the Indonesian island of Sulawesi, one dating to between 25,000 and 16,000 years ago, the other from 7,600 to 6,300 years ago.

Brumm says both hunter-gatherers display a "highly unusual" dental-wear pattern — deep, rounded tooth grooves — a novel bioarchaeological marker the researchers established was caused by a previously unknown drug-use behavior: habitual sucking of whole betel nuts.

Previous reports suggested the main neuroactive alkaloid in betel nut, known as arecoline, was released by chewing the processed nut in a prepared quid with slaked lime.

Brumm said: "Our team conducted experiments in which we soaked betel nuts in artificial saliva and tested the resultant broths against a panel of cloned human receptors expressed in frog egg cells, including specialized proteins that act as molecular switches, regulating neural activity.

"This showed that just sucking on intact betel nuts will release arecoline in sufficient amounts to have a physiological effect, altering brain function."

Biochemical analysis conducted by ARCHE Professor Carney Matheson also detected the presence of arecoline in the dental tissues of the foragers, providing strong evidence for betel nut ingestion.

Taken together, the research team said their findings suggest early foragers in Sulawesi engaged in an "ancient and longstanding practice" of habitually sucking betel nuts, resulting in dramatic alterations to their teeth.

While the psychoactive "high" of sucking betel nuts may have been milder than modern quid chewing, the researchers suggest the habit was significant enough to cause severe periodontal disease.

Ancient foragers on the island generally had bad teeth, and arecoline is a natural painkiller, so the team suspected one reason for betel nut-sucking was to alleviate the discomfort of toothache.

Brumm said: "Over time, however, sucking these hard, abrasive seeds wore down the foragers' teeth so badly that in some cases the inner pulp chamber became completely exposed – this would have been extremely painful, caused difficulty eating, and greatly increased the rate of chronic tooth infection.

"So while this habit may have been a remedy for toothache, years of prolonged nut-sucking eventually caused much worse dental health problems, creating a cycle of continued habitual use."

He said the finding marks a "significant shift" in understanding of human drug history, as the practice of using betel nut can now be traced to the Late Pleistocene period.

Brumm added: "Emerging by up to 25,000 years ago in Sulawesi, thus long preceding the onset of agriculture, betel nut-sucking may be the earliest evidence for drug use anywhere in the world.

"By identifying the ancient practice underlying betel-nut chewing as we know it, the study implies that some modern drug-taking behaviors are deeply rooted in forager traditions."

He says the findings also suggest habitual psychoactive substance use — and its associated health costs — were already present among hunter-gatherers tens of thousands of years before agriculture.