(CN) – A study of chemical residue in incense burners from ancient burials at high elevations in western China has revealed some of the earliest evidence of the use of cannabis for its psychoactive compounds, according to research published Wednesday in the journal Science Advances.
Cannabis has been cultivated for millennia in East Asia as an oil-seed and fiber crop, yet little is known about its more controversial and popular medicinal and psychoactive uses. Also referred to as marijuana, weed and pot, among other names, it has often been mired in controversy but more recently features in efforts to legalize its recreational and medicinal use in Europe and the Americas.
Researchers from the Max Planck Institute for the Science of Human History, the Chinese Academy of Sciences and the Chinese Academy of Social Sciences identified psychoactive compounds preserved in 2,500-year-old funerary incense burners from the Jirzankal Cemetery in the eastern Pamir Mountains, a range in Central Asia at the junction of the Himalayas. The discovery indicates ancient people selected plants with higher levels of the main psychoactive compound found in cannabis, tetrahydrocannabinol (THC), and burned them as part of burial rituals.
It is still unclear whether the people buried at Jirzankal cultivated cannabis or simply sought out higher plants with higher levels of THC. From at least 4000 B.C., the cannabis plants grown in East Asia for their oily seeds and fiber contained low levels of mind-altering THC.
But it has been a long-standing mystery as to when and where specific varieties of the plant with higher levels of psychoactive compounds were first recognized and used by humans. Increased ultraviolet radiation and other stressors related to growing at higher elevations will cause cannabis plants to produce greater quantities of active compounds, so it’s possible people roaming alpine regions may have discovered more potent wild plants there and began using them.
What we know about the origins of smoking cannabis come from a single passage written by the Greek historian Herodotus, found within an ancient text dating from the late first millennium B.C. Until now, archaeologists had little concrete evidence of cannabis smoking in Eurasia to back up Herodotus’ reference.
The international research team used gas chromatography-mass spectrometry to isolate and identify compounds preserved in the funerary incense burners. To their surprise, the chemical signature of the isolated compounds was an exact match to the chemical signature of cannabis – and also indicated a higher level of THC than is normally found in wild cannabis plants.
The research, by archaeologists and laboratory scientists from Germany and China, corroborate similar findings in burials farther north in the Xinjiang region of China and in the Altai Mountains of Russia.
"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." Max Planck Institute director Nicole Boivin said in a statement.
Whether cannabis had other uses for the early people of the Pamir Mountains is unclear, though it seems likely the plant's ability to treat a variety of illnesses and symptoms was recognized early on according to researcher Yimin Yang of the University of the Chinese Academy of Sciences in Beijing.
"This study of ancient cannabis use helps us understand early human cultural practices, and speaks to the intuitive human awareness of natural phytochemicals in plants," Yang said. "Biomarker analyses open a unique window onto details of ancient plant exploitation and cultural communication that other archaeological methods cannot offer."
The researchers recognize that while modern perspectives on cannabis vary tremendously cross-culturally, the plant has a long history of human use.
“Given the modern political climate surrounding the use of cannabis, archaeological studies like this can help us to understand the origins of contemporary cultural practice and belief structures – which, in turn, can inform policy," Boivin concluded.
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