Chewing coca in South America began by at least 8000 cal BP: our authors found and identified coca leaves of that date in house floors in the Nanchoc Valley, Peru. There were also pieces of calcite - which is used by chewers to bring out the alkaloids from the leaves. Excavation and chemical analysis at a group of neighbouring sites suggests that specialists were beginning to extract and supply lime or calcite, and by association coca, as a community activity at about the same time as systematic farming was taking off in the region.