Cannabis has been cultivated for millennia in East Asia as an oil-seed and fibre crop. Little is known, however, about the early use and eventual cultivation of the plant for its psychoactive and medicinal properties. Despite being one of the most widely used psychoactive drugs in the world today, there is little archaeological or historical evidence for the use of marijuana in the ancient world. A new study, published in the journal Science Advances, identifies psychoactive compounds preserved in 2,500-year-old funerary incense burners from the Jirzankal Cemetery in the eastern Pamirs. Researchers from the Max Planck Institute for the Science of Human History, the Chinese Academy of Sciences, and the Chinese Academy of Social Sciences have shown that people were selecting plants with higher levels of THC and burning them as part of mortuary rituals. This is the earliest clear evidence to date of cannabis being used for its psychoactive properties.