in recent times, but historians have been sifting through artifacts related to cannabis for decades. According to new evidence discovered high in the mountains of Asia, people were toking long, long .
A team of international researchers analyzed chemical residue found in wooden incense burners recovered from 2,500-year-old tombs in China's eastern Pamir mountain range and concluded that people were selecting plants with higher levels of THC -- the most potent psychoactive component in cannabis -- and burning them as part of mourning rituals.
While historians trace the origins of cannabis smoking to the ancient Central Asian steppes, they've largely relied on written accounts of the practice from the late first millennium BC rather than concrete proof.
The evidence described Wednesday in the journal Science Advances is thought to be some of the earliest yet of cannabis being used as a mind-altering substance. Most archaeological reports of ancient drug remains were published several decades ago, and some were later refuted as misleading, the study notes.
"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," said Nicole Boivin, director at the Max Planck Institute for the Science of Human History in Jena, Germany. The Institute conducted the research with the Chinese Academy of Sciences and the Chinese Academy of Social Sciences.
Archaeologists from the Chinese Academy of Social Sciences were excavating in the high mountainous regions of eastern China when they discovered the incense burners at a cemetery called Jirzankal, where people buried loved ones in tombs covered with circular mounds, stone rings and striped patterns using black and white stones. The region once served as an important culture communication channel through Eurasia, linking ancient populations in the modern regions of China, Tajikistan and Afghanistan.
The team extracted organic material from 10 wooden fragments and 4 burned stones and analyzed the objects using gas chromatography-mass spectrometry, which separates chemicals so they can be more easily identified.
To their surprise, the chemical signature of the isolated compounds exactly matched the chemical signature of cannabis. What's more, they discovered a higher level of THC than is normally found in wild cannabis plants. No clear evidence exists for smoking pipes in Central Asia before the modern era, according to the study, so people likely just inhaled the fumes.
"Modern perspectives on cannabis vary tremendously cross-culturally," Boivin said, "but it is clear that the plant has a long history of human use, medicinally, ritually and recreationally, over countless millennia."