Time, Ritual, and Bayesian Reasoning: Charting the Andean Kotosh Religious Tradition

Abstract Bayesian chronological modelling offers new leverage for reassessing the tempo and trajectory of early Andean ritual systems. Here I re-evaluate 168 radiocarbon determinations from 16 Late Archaic and Formative sites associated with the Kotosh Religious Tradition (KRT) using an OxCal workflow that combines rigorous sample vetting, outlier modelling, and Monte Carlo–derived Kernel Density Estimation. The resulting high-precision sequences reveal that KRT ceremonial architecture arose virtually simultaneously on Peru’s central coast and in the adjacent highlands by ~ 3600 cal BCE, refuting long-standing diffusionist scenarios that posit a unidirectional spread from one heartland to another. Six statistically robust ritual phases are defined, each bracketed by ≥ 95% highest-posterior-density intervals. Probability distributions for phase boundaries and inter-regional offsets indicate recurrent, multidirectional exchange rather than linear succession. This pattern implies a distributed network of communities negotiating a shared but diversely expressed ritual repertoire, rather than a single center exporting an ideological package. Beyond clarifying KRT chronology, the study demonstrates how transparent “chronological hygiene” protocols paired with Bayesian phase-break analysis can resolve fine-grained cultural dynamics in other early complex societies.