ABSTRACT: Behaviors like breathing and locomotion are based on patterns of rhythmic movements that emanate from brain networks. What makes these networks of neurons oscillate? One longstanding hypothesis is that 'pacemaker' neurons play a central role, which we evaluate here in the respiratory network of mammals. Breathing is an ideal model system because respiratory activity is preserved in reduced preparations from neonatal rodents in vitro, which facilitate the study of neural mechanisms in detail. Here use these powerful in vitro preparations and the testable predictions of mathematical models to show that pacemaker neurons are not essential for rhythm generation. Instead, we propose that respiratory rhythm is an emergent network property. This represents a major paradigm shift since brain rhythms are oftentimes assumed to be pacemaker-driven.