An international research team led by the University of Bern has discovered cannabis seeds and molecular traces of cannabis compounds in human hair in a princely tomb in Siberia. Radiocarbon dating places the seeds in the early 8th century BC; according to the researchers, this is the oldest directly dated evidence of psychoactive cannabis use to date. The study was published in „Science“ (DOI: 10.1126/science.aeg3800).
Cannabis is one of the most widely consumed psychoactive plants, but determining its prehistoric use archaeologically is difficult because plant parts such as flowers, leaves and resins are perishable. Cannabis is known to have served various purposes, including oil or fibre production. The team led by Gino Caspari of the Institute of Archaeological Sciences at the University of Bern and the Max Planck Institute of Geoanthropology combined various analytical methods in a princely tomb in the southern Siberian republic of Tyva. The tomb belongs to a high-ranking person of the Scythians, a equestrian culture of the Eurasian steppe; around 1,000 cannabis seeds were recovered. Six seeds were directly radiocarbon-dated. Together with further dating, the results point to deposition in the early 8th century BC. „The seeds show that cannabis played an important role in the rituals surrounding the burial,“ Caspari said.
The seeds come from wild or feral plants; whether they were deliberately cultivated cannot be deduced, and their presence in the tomb alone does not prove psychoactive use. That emerged only from the analysis of preserved human hair from the central burial chamber. In several hair samples, the researchers found clear signals consistent with cannabinol (CBN); CBN forms, among other things, through the oxidation of tetrahydrocannabinol (THC), the main psychoactive compound in cannabis. The team also registered weak signals compatible with THC based on their mass. The analysis used high-resolution mass spectrometry, among other methods.
According to the researchers, the hair analyses indicate cannabis consumption but do not allow reliable determination of the amount consumed. Nor can it be established with certainty whether the compounds were inhaled or eaten. Later archaeological sites in Central Asia show chemical residues of cannabinoids in vessels and on heated stones, clearly indicating inhalation. „The molecular traces in the hair and the cannabis seeds come from the same tomb and suggest that cannabis was used for its psychoactive properties,“ Caspari said.
The team places the finds in a ritual burial context. „In this princely tomb, the burials were accompanied by extensive horse sacrifices and probably also human sacrifices,“ Caspari said. In an earlier publication, the team had found the remains of 18 horses once displayed on the burial mound; in the meantime, several dozen more horse sacrifices and scattered human bones have come to light. The results provide what is probably the oldest directly dated archaeological evidence of cannabis use for its psychoactive properties. They do not, however, allow conclusions about the THC content of the plants at the time or whether they were deliberately selected or cultivated for higher potency.
The team is currently investigating further properties of the recovered plant remains. „We have already begun sequencing some of the plant samples. DNA preservation in this case is excellent. This will help us soon learn more about the history of domestication and spread of this cultivated plant,“ Caspari said. He is the contact person at the Institute of Archaeological Sciences at the University of Bern.
