One of the braziers recovered from the grave site. Some had residues from cannabis smoking in them. (Credit: Xinhua Wu)

More than 40 tombs dot the southeastern corner of the Pamir plateau, a desert landscape at nearly 10,000 feet elevation in far western China’s high mountains. Buried with the dead is evidence that whoever put them there also conducted rituals at the site more than two millennia ago. And those ceremonies involved a certain hallucinogenic plant we know quite well today: canna