A team of Griffith University archaeologists has uncovered evidence that humans were using mind-altering substances much earlier in time than previously supposed.
Led by Professor Adam Brumm from Griffith's Australian Research Centre for Human Evolution (ARCHE), and involving ARCHE colleagues Associate Professors Carney Matheson and Michelle Langley, the team combined biochemical and archaeological evidence to trace the prehistoric roots of one of the world's most popular addictive stimulants, "betel nut", an ancient drug used throughout much of the Asia-Pacific region.
The group's research, conducted in collaboration with Indonesian archaeologists from Makassar's University of Hasanuddin and the National Research and Innovation Agency (BRIN), shows that the use of betel nut as a drug emerged among some Indonesian communities by up to 25,000 years ago, moving beyond the previously suggested Neolithic or Bronze Age (~3,500 years ago) start times.
Current theories on the earliest history of drug-taking
Presently, it is thought the world's first traditions of psychoactive drug use arose after the Neolithic advent of farming, beginning with the innovation of fermented alcoholic drinks (barley beer) about 13,000 years ago in Israel.
"However, this theory fails to account for the possibility that very ancient drug-taking lies at the roots of our most commonly used psychoactive substances," Professor Brumm said.
Professor Brumm's investigation focused on the origins of betel nut usage, a near-universal tradition among hundreds of millions of people between India and the South Pacific (about one in 10 of the modern global population).
Consuming betel nut induces a sense of mild euphoria and heightened alertness, among other effects.
"Although poorly known in western societies, it is the world's fourth most widely used psychoactive substance, after alcohol, caffeine and nicotine," Professor Brumm said.
Modern users 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.
"Slaked lime is an essential ingredient because it causes a chemical reaction that releases the nut's psychoactive compounds into the bloodstream more rapidly," Professor Brumm said.
The early history of this drug use practice had remained uncertain, largely because areca seeds were rarely preserved at archaeological sites.
Discovery reveals prehistoric drug use
In the new study, published in Science Advances, the Griffith team reports the discovery of extremely rare skeletal remains of two early human foragers from the Indonesian island of Sulawesi, one dating to 25,000-16,000 years ago, the other to 7,600-6,300 years ago.
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 behaviour: habitual sucking of whole betel nuts.
Previous reports suggested the main neuroactive alkaloid in betel nut (arecoline) was released by chewing the processed nut in a prepared quid with slaked lime, with the latter converting arecoline into a free base form, thereby increasing its bioavailability.
"But 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 specialised proteins that act as molecular switches, regulating neural activity," Professor Brumm said.
"This showed that just sucking on intact betel nuts will release arecoline in sufficient amounts to have a physiological effect, altering brain function."
In addition, biochemical analyses carried out by Associate Professor Carney Matheson detected the presence of arecoline in the dental tissues of the foragers, providing strong evidence for betel nut ingestion.
Taken together, the 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.
Bad medicine
While the psychoactive "high" of sucking betel nuts may have been milder than modern quid chewing, the team suggested the habit was significant enough to cause severe periodontal disease.
Ancient foragers on this island generally had bad teeth, and arecoline is a natural analgesic ("painkiller"), so the team suspected one reason for betel nut-sucking was to alleviate the discomfort of toothache.
"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," Professor Brumm said.
"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."
Earliest evidence for drug use
This finding marks a significant shift in our understanding of human drug history, as the practice of using betel nut can now be traced to the Late Pleistocene period.
"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," Professor Brumm said.
"By identifying the ancient practice underlying betel-nut chewing as we know it, the study implies that some modern drug-taking behaviours are deeply rooted in forager traditions."
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.
The study 'Betel nut sucking is the earliest recorded evidence for the habitual use of a neuroactive plant drug' has been published in Science Advances.
