Can we reliably detect adaptive responses of hunter-gatherers to past climate change? Examining the impact of Mid-Holocene drought on Archaic settlement in the Basin-Plateau Region of North America

Climatic change appears to influence major patterns in human history. However, confirming the association between climatic events and adaptive human responses is not straightforward given the potential for spurious correlations and uncertainty in the timing of events. Here we leverage theory from behavioral and population ecology to generate predictions about causal relationships between climate and settlement decisions. We then test those predictions using statistical methods designed to evaluate the likelihood of associations under uncertainty. This allows us to evaluate a comprehensive record of radiocarbon dated archaeological sites in the Basin-Plateau region of North America relative to a record of effective precipitation reconstructed using Macrophysical Climate Models. Consistent with theory, the results show that regional populations declined in the mid-Holocene during a prolonged period of reduced precipitation, leading to the abandonment of many major rockshelter sites. Remaining populations concentrated at open-air sites around well-watered sand dune localities where they constructed pithouses and adopted more intensive subsistence practices. These findings illustrate an adaptive response of hunter-gatherer populations to past climate change that supports theoretical predictions and is unlikely to result from spurious correlations or uncertainties in the timing of events.