Social change and late Holocene hydroclimate variability in southwest Indiana

The archaeology of how communities in the North American midcontinent responded to environmental change has had global significance for understanding hydroclimate-human relationships in non-industrialized societies. We evaluate how an agriculturalist settlement network, the Angel polity, coped with environmental change through comparing the radiocarbon-derived occupation history to local proxies for hydroclimatic change from Martin Lake, Indiana. Located within the northeast Mississippian (AD 1000–1500) frontier, the Angel polity consisted of a network of hamlets and villages, encompassing ∼800 km² in southwest Indiana with the Angel Mounds site serving as the polity’s social nexus. The results indicate that Angel Mounds was established as the Medieval Climate Anomaly transitioned to Little Ice Age (LIA) drought with the construction of a community centered around a platform mound earthwork. The Angel polity’s population became more centralized at Angel Mounds during the initial decades of the LIA drought conditions and a large fortification was constructed at Angel Mounds during this time. The dissolution of the Angel polity occurred in AD 1350–1450 during a profound LIA-associated mega-drought and regional depopulation of the midcontinent. These results provide an example of how non-industrialized, agriculturalist communities responded to episodes of hydroclimatic change.