Archaeologists have uncovered what a new study describes as the earliest evidence of people consuming cannabis for psychoactive purposes. The discovery came from a monumental elite tomb in southern Siberia that dates back almost 3,000 years.

At the tomb in the Uyuk Valley, researchers recovered preserved cannabis seeds alongside human hair. Lead study author Gino Caspari, a researcher at the University of Bern in Switzerland, said the unusual combination moved the subject beyond long standing speculation.

“There is a lot of speculation about prehistoric use of plant-based drugs, but through this find we are actually able to show that there is a basis to it,” Caspari told CNN.

The tomb contained the remains of various high status individuals, and Caspari and his colleagues have worked at the site since 2017. Their evidence dated the tomb to 2,800 years ago, during the earliest Scythian period.

“These were nomadic horse-back riders known for their skill of shooting from horseback and for their exquisite gold items,” Caspari said.

At the site, the researchers noticed small black dots inside the tomb and identified them as cannabis seeds. They ultimately recovered more than 1,400 seeds, while radiocarbon dating indicated that the material had been deposited around 2,800 years ago.

The team also recovered preserved human hair and tested it with a mass spectrometer. The analysis detected THC, or delta-9-tetrahydrocannabinol, the primary psychoactive compound in cannabis, as well as cannabinol, which is produced when THC is exposed to air.

“Surviving plant remains which are almost 3,000 years old are extremely rare,” Caspari told CNN, as they are generally poorly preserved. “It is even rarer to find them in combination with human soft tissue like hair, which essentially allows (us) to drug test a person who has been dead for three millennia.”

“That was just an amazing moment,” Caspari said. He said the discovery expands understanding of the history of cannabis consumption.

Scientists had previously found evidence that cannabis was cultivated in East Asia at least 6,000 years ago, probably for its oil rich seeds, according to a statement from the researchers. Evidence that people used the plant for mind altering effects had previously reached back 2,500 years, including ritual practices in Central Asia.

“The cannabis use has to be seen in a ritual context in the tomb and may be connected to shamanistic beliefs,” Caspari told CNN. The setting included dozens of sacrificed horses and some potential human sacrifices, but the plant’s precise purpose remains uncertain.

“Since we have dozens of sacrificed horses and some potential human sacrifices it might also have been used to sedate the victims before something bad happened to them — but we cannot prove that,” Caspari said.

“Surprisingly little is known about the deep time cultural history of this important crop. For example, we are not even sure what truly wild cannabis actually looks like,” he added.

“Now we have at least 3,000 years of psychoactive cannabis consumption on the Eurasian continent and it seems that at this point it was already spread from China to Europe,” Caspari said. “We think this provides a cultural anchor point for current debates on legalization and medical use of the plant.”

The team is now sequencing the ancient DNA from the seeds recovered at the site. “Having well-preserved plant DNA is even rarer than having plant remains and this is the oldest preserved cannabis DNA,” Caspari said.

“In the next few years our team will probably rewrite part of the domestication history of cannabis,” Caspari said.

Roger Forshaw, an honorary lecturer in biomedical Egyptology at the University of Manchester in England who was not involved in the study, said the research “provides some fascinating insights into the use of cannabis among early Iron Age communities in Central Asia, a practice for which direct archaeological evidence has previously been scarce.”

Forshaw said the chemical traces found in the hair “provides direct molecular evidence of cannabis use and supports the interpretation that it formed part of the funerary rituals.” He added that the method of administration and exact role in the burial rituals remain uncertain.

“Although we cannot be certain how the plant was administered or precisely what role it played in the burial rituals, the discovery adds considerably to our understanding of the use of psychoactive plants in ancient societies,” Forshaw said. The study was published Thursday in the journal Science.