An international team of archaeologists has found evidence that hunter-gatherers on the Indonesian island of Sulawesi were chewing areca nuts for energy and pain relief as far back as 25,000 years ago, long before humans took up farming.
The findings, drawn from analysis of dental fossils, represent the oldest known evidence of habitual use of a neuroactive plant drug by humans, according to the researchers, who examined the remains of two pre-agricultural foragers from the island.
Until now, scientists believed that consumption of psychoactive plants such as the areca nut began with the arrival of farming societies in the Neolithic period, or with the spread of Austronesian populations roughly 4,000 years ago. The exact origins of the habit had remained uncertain.
The areca nut is considered the fourth most popular psychoactive substance in the world, behind alcohol, caffeine and nicotine. It is typically chewed today as part of a mixture that also includes slaked lime, a form of calcium hydroxide or carbonate, and betel leaf, a plant from the same family as pepper. The lime helps the nut's active compound reach the body faster and produces the reddish stain associated with betel chewing.
The Sulawesi discoveries
Researchers examined the skeletal remains of two pre-agricultural foragers found on Sulawesi. One, known as Maros-LBB-1a, from the Leang Bulu Bettue site, consists of an upper jaw with molars dated to the Late Pleistocene, between 25,000 and 16,000 years ago. The Late Pleistocene is the geological period that ended around 11,700 years ago.
The second, CPL-R2a, from the Leang Cappalombo 1 site, is the skeleton of an adult man linked to the Toalean culture, described by the researchers as a little-understood group of hunter-gatherers, dated to the Middle Holocene, between 7,600 and 6,300 years ago.
Both individuals showed a pattern of severe dental wear, rounded and grooved furrows in the teeth, that had never before been formally described in archaeological literature. Neither set of teeth carried the intense reddish staining typical of modern betel chewing with lime, ruling out use of the traditional lime-based preparation.
The wear marks measured 10 to 20 millimetres in diameter, a shape and size that point to the prolonged habit of holding a hard, round object, such as a whole areca nut, between the teeth and gently gnawing it over long periods.
Testing the chemistry
To find out whether simply sucking on a whole nut, without lime or crushing, could release enough active compounds to affect the brain, the researchers ran laboratory tests. The experiments showed that sucking a whole nut releases arecoline, the plant's main active compound, in quantities sufficient to produce bodily effects such as excess saliva production.
Sucking the whole nut released low molecular weight active compounds but not the high molecular weight compounds linked to more severe inhibitory or toxic effects, the team found.
Arecoline was detected directly on the teeth of both ancient skeletons, chemically confirming that the individuals had consumed betel nut. The researchers found no significant quantities of the compounds that form in abundance only when the nut is mixed with slaked lime, confirming that these early humans ate the nut without lime.
The analysis also turned up aromatic compounds from betel leaf, suggesting the leaves may have been consumed separately, possibly for their scent or for medicinal purposes.
Rewriting the timeline
The study pushes back the earliest known evidence of habitual use of a neuroactive plant drug to between 25,000 and 16,000 years ago, showing that the behaviour predates agriculture by thousands of years.
