Betel nut sucking is the earliest recorded evidence for the habitual use of a neuroactive plant drug.

The modern custom of chewing betel nuts is practiced by around 1 in 10 people worldwide, yet the earliest beginnings of this widespread drug use habit are unknown. We report rare skeletal remains of two preagricultural foragers from Sulawesi (Indonesia), both displaying a dental pathology that we establish was caused by a hitherto unknown precursor to betel chewing: habitual sucking of whole betel nuts. Previous reports suggested that the main neuroactive alkaloid in betel nut, arecoline, is released by masticating the processed nut with slaked lime. However, our experiments demonstrate that simply keeping intact betel nuts in the oral cavity for prolonged periods releases arecoline. Biomolecular analysis of the ancient human teeth is also consistent with this early form of ingesting betel nut. With the earliest forager dating to 25 to 16 thousand years ago, our findings suggest the use of betel nut as a drug has more ancient origins than previously supposed.