Researchers have discovered evidence of ritual cannabis smoking in western China from 2,500 years ago, suggesting the earliest use of the drug for its psychoactive effects.

A study published Wednesday in the journal Science Advances analyzed archaeological artifacts from burial grounds on the Pamir Plateau, with a chemical analysis of burn marks on the objects indicating cannabis with “high levels of psychoactive compounds.” Meanwhile, human bones and a harp also discovered at the site, among other artifacts, suggest that ritual and religious practices took place at the grounds.

Researchers say these clues show that cannabis smoking played an important role in burial rituals. “We can start to piece together an image of funerary rites that included flames, rhythmic music, and hallucinogen smoke,” they wrote, “all intended to guide people into an altered state of mind.” (Image: Science Advances)