Archaelogists have found the oldest known evidence of cannabis inhalation, and boy did those old cats know how to party.

The ruins of a 2,500-year-old sesh shows indications that the tokers of yore used “high potency” cannabis to commune with spirits and maybe even in their ritual sacrifices.

Chinese researchers in the Jirzankal cemetery of Pamir mountains made the discover after analyzing recently excavated wooden braziers. After scraping some resin out of the artifacts, they ran it through a mass spectrometer and found cannabinol, which indicates the former presence of oxidized THC.

They also found comparatively little amounts of other cannabinoids, which suggests that the plants were chosen specifically for their full-on THC goodness. It’s unknown whether the plants were found in the wild or cultivated specifically to get the ancients blazed.

“To our excitement we identified the biomarkers of cannabis, notably chemicals related to the psychoactive properties of the plant,” Yimin Yang of the University of Chinese Academy of Sciences in Beijing told The Guardian.

Almost all of the braziers found contained evidence of cannabis, “implying that the braziers were being used during funeral rituals, possibly to communicate with nature, or spirits or deceased people,” Yang said.

Archaeologists also found skeletons interred at the site, some with “holes in their skulls and what appear to be fatal cuts and breaks to their bones, raising the possibility that at least some of the dead were sacrificed,” according to The Guardian.

In addition to human sacrifice, the ancient people had some other interesting facets to their cannabis use, including an unusual method for smoking. Researchers believe that stones were cooked in a fire, then put in the braziers and covered with weed, which billowed cannabis smoke to those who partook. Party.

Photo of the Pamir Mountains via Flickr user S Nazari