Chemical analysis of several wooden braziers recently excavated from tombs in western China provides some of earliest evidence for ritual cannabis smoking, researchers report. The study suggests that smoking cannabis for ritual and religious activities was practiced in western China by at least 2500 years ago, and that the cannabis plants involved were producing high levels of psychoactive compounds, indicating that people were aware of and interacting with specific populations of the plant. Cannabis, one of the oldest cultivated plants in East Asia, is also one of the most widely used psychoactive drugs in the world today. However, little is known about its early psychoactive use or when plants under cultivation evolved to produce higher levels of psychoactive compounds. Most evidence for early use of cannabis for its psychoactive properties comes from written records, where scholars question reliability; the archaeological evidence for ritualized consumption of this plant is limited. Recently, ten wooden braziers containing stones with obvious burning traces were exhumed from eight tombs at the Jirzankal Cemetery, which dates to approximately 2500 years ago. Meng Ren and colleagues suspected the braziers may have had a specific ritual function. To investigate, they extracted organic material from the wooden fragments and burnt stones and analyzed them using gas chromatography-mass spectrometry. To their surprise, the results showed an exact match to the chemical signature of cannabis, particularly that with a high amount of tetrahydrocannabinol (THC), the most potent psychoactive agent in the plant. Smoking was likely performed during burial ceremonies, perhaps as a way to communicate with the divine or the dead, the authors say. This study further highlights the importance of residue analyses, which could open a unique window onto details of cultural communication in the past that other archaeological methods cannot offer.