Humans may have been using mind-altering substances thousands of years earlier than previously believed, according to new research suggesting that people in Indonesia were using betel nuts as a psychoactive drug up to 25,000 years ago.

Researchers from Australia’s Griffith University found unusual patterns of wear on the teeth of early human foragers on the Indonesian island of Sulawesi. The wear suggests they regularly sucked whole betel nuts.

Professor Adam Brumm, who led the study, described the findings as potentially the “earliest evidence for drug use anywhere in the world”.

The study, published in Science Advances, examined the skeletal remains of two early human foragers. One lived between 25,000 and 16,000 years ago, while the other lived between 7,600 and 6,300 years ago.

Both individuals had deep, rounded grooves on their teeth. Experiments by the researchers indicated that the unusual wear was caused by repeatedly sucking whole betel nuts.

Betel nuts are the seeds of the Areca catechu palm. They contain psychoactive compounds that can produce mild euphoria and increased alertness.

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

Until now, researchers have generally believed that widespread drug use emerged after the development of farming, with fermented alcoholic drinks appearing around 13,000 years ago.

Brumm said this theory may overlook much older traditions of using naturally occurring psychoactive substances.

The researchers said the findings suggest that some modern drug-taking practices may have their origins in the traditions of ancient hunter-gatherer communities.

Today, betel nuts are commonly consumed by processing the seed with slaked lime and other ingredients to make a chewable mixture known as a “quid”. The practice remains widespread across South and Southeast Asia.

To investigate whether simply sucking whole betel nuts could produce psychoactive effects, the researchers soaked them in artificial saliva. They found that the process released enough psychoactive compounds to potentially affect brain function.

The effects would likely have been weaker than those produced by modern betel-nut chewing, but researchers believe the ancient practice was still significant enough to contribute to severe gum disease.