There were some non-tobacco plants in ancient pipes. Washington State University researchers have found that Rhus glabra, a plant commonly known as Smooth Sumac was smoked more than 1,400 years ago in what today is north America. Smoking often played a religious or ceremonial role for Native American tribes and research shows these specific plants were important to these communities in the past. Analysis of the pipes used by the ancient people shows how they used specific smoking plant mixtures. Rhus glabra may have been mixed with tobacco for its medicinal qualities and to improve the flavour of smoke. The study will help scientists identify which plant species ancient people were consuming, providing important information about the evolution of drug use and similar plant-human dynamics.