Absolute Chronology revisited: Integrating precise Bayesian models from Machu Picchu with Inca ethnohistoric praise narratives

Abstract

Recent articles provide a captivating set of radiocarbon dates from Machu Picchu and environs, with important ramifications for the site and the Inca Empire more broadly. Here, we present Bayesian models of these dates that incorporate life history details of each dated individual, including age at death, age of tissue formation for dated samples, family relationships, and associated grave goods. We calibrate dates with a bespoke calibration curve mixture specific to Machu Picchu. These model boundaries suggest the site was first occupied ∼ AD 1435 (1410–1455, 95%) and abandoned ∼ AD 1495 (1480–1515, 95%). This is consistent with dates from the region and builds on the consensus that ethnohistoric dates are unreliable. Anchoring Inca history to this radiocarbon chronology allows us to explore the ethnohistoric sources in a new light. We can more plausibly trace the life history of the ruler Pachacutec, including his founding of the Machu Picchu royal estate. Regionally, this approach leads us to reassess the conquest of the earliest and largest Inca conquest, the southern quarter. This area was subject to waves of intense interaction for nearly two centuries by multiple royal houses, possibly starting under Yahuar Huacac, Pachacutec's grandfather, events that were almost completely scrubbed from Inca praise narratives.