The broken wooden braziers, unearthed from 2,500-year-old tombs in Western China, contained burned, blackened stones, and the interior of the wooden vessels also looked charred. To find out what had been burned in them, University of Chinese Academy of Sciences archaeologist Yemin Yang and his colleagues used gas chromatography/mass spectrometry to analyze small samples of the charred wood and the residue from the stones.

Their analysis turned up a chemical called cannabinol, or CBN—an unmistakable chemical signature of cannabis. Those ancient chemical traces offer an important clue in the history of human drug use and the domestic history of cannabis.

In around 500 BCE, the ancient Greek historian Herodotus described people near the Caspian Sea gathering in small, enclosed tents to breathe in the smoke from cannabis burned atop a bowlful of red-hot stones. Yang says people did something similar at Jirzankou, probably as part of funeral ceremonies. Archaeologists there also found the remains of a musical instrument called an angular harp, which played an important role in later funeral rites in Western China.