The earliest evidence of human's smoking cannabis to get high has been discovered in a 2500-year-old tomb in Central Asia, according to a research paper published in the Science Advances journal.
Cannabis residue has been located at other archaeological sites from the same time period before. However, this latest find is the first direct evidence suggesting cannabis was used for psychoactive purposes as well as for rituals, National Geographic reports.
A chemical analysis of the braziers showed that nine of the ten stones contained cannabis.
Scientists subsequently discovered that the Jirzankal cannabis contained molecular remnants of tetrahydrocannabinol, or THC. THC is the chemical in cannabis that generates its psychoactive effects.
The publication reports that the residue found at Jirzankal displayed higher levels of psychoactive, mood-altering compounds - making the pot reportedly more potent than any other ancient cannabis found thus far.
Researchers have said this finding presents the first clear evidence suggesting ancient civilisations used cannabis to experience psychoactive effects.
Mark Merlin, an ethnobotanist and cannabis historian at the University of Hawaii, told National Geographic: "It's a real indication of how long humans have been manipulating cannabis."