Ethnopharmacology combines ethnographic fieldwork among the people who use a traditional medicine or ritual substance with laboratory testing of that substance's actual pharmacological activity, checking a traditional healing or entheogenic claim against measured biological effect rather than accepting or dismissing it on its own terms. The field took its name and its first organized statement from a 1967 conference in San Francisco on the ethnopharmacologic search for psychoactive drugs, organized by Daniel Efron, Bo Holmstedt and Nathan Kline, which brought pharmacologists and anthropologists together to study traditional psychoactive plant use as a serious joint subject for the first time.
Ritual healing practice, shamanic plant medicine and entheogenic sacrament use appear across many traditions with specific claimed effects, and ethnopharmacology is what lets the atlas say whether a named plant's traditional use corresponds to a documented pharmacological action, distinct from whether the tradition's own account of why it works, spiritual, humoral or otherwise, is itself testable. The atlas cites ethnopharmacological findings wherever a tradition's medicinal or entheogenic plant claim can be checked against laboratory evidence.