ABSTRACT Although archaeologists often highlight the capacity of our field to identify broad-scale patterning in human societies, critiques of social evolution led many to focus on shorter-term, local histories. Drawing from a recent review of alternative models, we employ firefly synchronicity – the rhythmic coordination of flashing observed in some species of bioluminescent fireflies – as a model for understanding patterning in the timing of platform mound construction by Indigenous peoples of Tampa Bay, on the western coast of the Florida peninsula, USA. Bayesian modelling of radiocarbon dates and isotopic studies of oyster shells from three neighbouring sites reveals rhythmic coordination in the construction of platform mounds across the first millennium CE. We relate this patterning to interaction in seasonal and longer-term ritual cycles which may have facilitated collective management of zero-sum common property resources. Firefly synchronicity provides a useful model for identifying patterning in archaeological phenomena without much of the baggage of social evolution.