AbstractThe environment impacts human health in profound ways, yet few theories define the form of the relationship between human physiology and the environment. It is conjectured that such complex systems cannot interact directly, but rather their interaction requires the formation of an intermediary “interface.” This position contrasts with current epidemiological constructs of causation, which implicitly assume that two complex systems transfer information directly while remaining separate entities. Further, it is contended that dynamic, process‐based interfaces incorporate components from all the interacting systems but exhibit operational independence. This property has many consequences, the foremost being that characteristics of the interface cannot be fully resolved by only studying the systems involved in the interaction. The interface itself must be the subject of inquiry. Without refocusing the attention on biodynamic interfaces, how the environment impacts health cannot be discerned. Also see the video abstract here https://youtu.be/XeyjeZeyo4o.