An ancient society in the Peruvian Andes likely used psychoactive drugs during exclusive rituals that may have helped establish social and political hierarchies seen later throughout the region, according to a new study.

The prehistoric Chavín people held private and potentially secret gatherings where elite figures used “snuff tubes” to consume tobacco and hallucinogenic plant residue with properties of DMT, which can be found in a wide variety of plants, said the study published Monday in the peer-reviewed journal Proceedings of the National Academy of Sciences. When ingested, DMT causes brief, episodic visual hallucinations, according to the National Institute of Health.

The study was conducted by a group of archaeologists and researchers from the United States and South America, who sought to investigate a centuries-old Chavín compound for evidence of drugs involved in the ritual practices already understood to be a central part of their culture. To do that, the team explored and analyzed artifacts found at Chavín de Huántar, a UNESCO World Heritage Site in the Andean highlands some 250 miles north of Lima.

Made from stone, the ruins there are believed to date back as far as 1200 B.C.E. The Chavín occupied that site and the region more broadly until around 400 or 500 B.C.E. and are considered a major predecessor to the better-known Inca civilization.

While previous research has pointed to ritual activity at Chavín de Huántar, and Chavín iconography raised questions about whether psychedelic plants were involved, the new study offered material evidence not seen before that hallucinogens were a focal point of those gatherings.

Daniel Contreras, an anthropological archaeologist and professor at the University of Florida who co-authored the study and has focused his work on Chavín de Huántar for about three decades, said in a statement released that consuming psychoactive drugs, in this context, “was part of a tightly controlled ritual, likely reserved for a select few, reinforcing the social hierarchy.”

At Chavín de Huántar, archaeologists discovered a network of hidden rooms they called galleries, built into the larger stone complex. Inside them, the team found 23 artifacts believed to be drug paraphernalia — mainly, tubes constructed from the bones of birds that researchers say functioned as apparatuses for inhalation.

Chemical tests subsequently conducted on those tubes revealed six of them contained traces of hallucinogenic substance dimethyltryptamine, or DMT, a powerful psychedelic that occurs naturally in plants and animals. In four of the six articles, researchers said they found microremains related to the roots of wild Nicotiana species — also known as tobacco plants — as well as vilca bean residue, a hallucinogen related to DMT.

Although research into the drug’s effects on humans largely acknowledges gaps in how medical and scientific fields currently understand the body’s reaction to it, some reports note that DMT causes a temporary and intense response in the brain that can result in those who’ve taken it to anecdotally recall visions and hallucinogenic revelations.

Contreras’ team contended in their study that the tubes discovered at Chavín de Huántar may not have been used exclusively for psychotropic rituals. But, when those rituals did take place, the small size of the rooms where they were found suggests that only certain members of the Chavín society were invited to partake. 

By offering access to altered states of consciousness, the ceremonies were integral to the creation of early class structures, providing an ideology that “justified or naturalized” inequality in social orders, Contreras said. Hallucinogenics potentially played a vital role in all of that, he told CBS News in an email.

“This is compelling evidence that psychoactive plants were part of formalized and tightly-controlled rituals rather than individual vision-quests or shamanic healing practices,” Contreras said. “As such, they seem to have been an important element in the long-term transition from small egalitarian societies to large stratified ones, where social, political, and economic inequality were thought of as normal and to be expected rather than unusual.”