Some 2,500 years ago, in present-day China, people were using cannabis to get high during rituals, scientists announced in a new study published Wednesday.
This is the first known use of weed by humans anywhere in the world, the study suggests.
"Modern perspectives on cannabis vary tremendously cross-culturally, but it is clear that the plant has a long history of human use, medicinally, ritually, and recreationally, over countless millennia," said study author Robert Spengler, an archaeobotanist at the Max Planck Institute for the Science of Human History in Jena, Germany.
The pot was likely smoked during burial ceremonies, perhaps as a way to communicate with the divine or the dead, the authors say.
“It’s the earliest strong evidence of people getting high” on marijuana, said Mark Merlin, a botanist at the University of Hawaii, who was not involved in the research.
Residue of the drug was discovered on ancient pots in tombs in the Pamir mountains, a region near the borders of modern China, Pakistan and Tajikistan, archaeologists said.
Using new techniques for chemical analysis, researchers examined the residue and found evidence of THC, the compound that gives pot its high. Most wild cannabis plants have low levels of THC, so scientists think the people who built the graves deliberately selected or cultivated plants with higher amounts.
The cannabis plants produced high levels of psychoactive compounds, which indicates that people were aware of and interacting with specific populations of the plant, said study co-author Nicole Boivin, also of the Max Planck Institute.
"The findings support the idea that cannabis plants were first used for their psychoactive compounds in the mountainous regions of eastern central Asia, thereafter spreading to other regions of the world," Boivin said.
Though remote today, the location in western China where the tomb was discovered may once have sat near a key ancient trade route of the early Silk Road. The Silk Road was at one time the single most important route for cultural spread in the ancient world, according to the study.
This allowed the drug to spread around the world.
"The exchange routes of the early Silk Road functioned more like the spokes of a wagon wheel than a long-distance road, placing Central Asia at the heart of the ancient world," Spengler said.
"Our study implies that knowledge of cannabis smoking and specific high-chemical-producing varieties of the cannabis plant were among the cultural traditions that spread along these exchange routes," he added.
The study was published in the peer-reviewed journal Science Advances, a publication of the American Association for the Advancement of Science.