A new study suggests people were using cannabis for psychoactive purposes at least 2,800 years ago. Archaeologists found evidence in a Siberian tomb, indicating cannabis use 300 years earlier than previously known in China. The team from Germany, Russia, Sweden, and Switzerland analyzed hair and cannabis seeds from the site. They said the findings shed light on the plant’s role in ancient societies. However, some experts are skeptical, saying the evidence is weak and doesn’t confirm drug use. The study was published Thursday in the journal Science.