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 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.

We develop and test a hypothesis here that the seasonality of temperature and precipitation played a major role in determining the population densities of artioclactyls (e.g., Ovis canadensis, Odocoileus hemionus, and Antilocapra americana) across the terminal Pleistocene and Holocene of western North America. For much of this region, general circulation climate models and a range of paleoclimatic data suggest that seasonal extremes in temperature peaked during the terminal Pleistocene and early Holocene and that early and middle Holocene precipitation followed a winter-wet, summer-dry pattern-conditions known to depress artiodactyl densities. These trends are mirrored in a northern Bonneville Basin macrophysical climate simulation model from which we derive terminal Pleistocene and Holocene climatic values and three indices of climatic seasonality: (1) intra-annual temperature range, (2) summer precipitation intensity, and (3) winter precipitation intensity. These indices are arrayed against three detailed late Quaternary artiodactyl abundance records in the Bonneville Basin: a unique paleontological record of fecal pellet densities, and archaeological records of artiodactyl skeletal elements and large game hunting tools. Each of these artiodactyl abundance records shows significant correlations with the model-derived seasonality indices and suggests that artioclactyls occurred in low densities from the terminal Pleistocene through the middle Holocene-substantial increases occurred during equable, summer-wet periods of the late Holocene. Archaeological vertebrate records from across western North America show very similar temporal patterns in artiodactyl abundances suggesting that the trend and its climate-based causes may be a very general one. These conclusions have far-reaching implications not only for our understanding of ancient human hunting and land use patterns, but for the future management of artioclactyls under scenarios of global warming that also project dramatic increases in extreme climate. (C) 2008 Elsevier Ltd. All rights reserved.

Excavations in 1964 at the Pine Spring site in southwest Wyoming concluded that the site contains three cultural occupation levels; the earliest allegedly dates to the terminal Pleistocene and is associated with megafauna. However, excavations in 1998 and 2000, and analysis of the stratigraphy, AMS dates, micromorphology, and artifact carbonate isotopes, along with debitage refitting, density, orientation, inclination, burning, and trample damage, could not replicate the 1964 findings. A hiatus in deposition accounts for the highest density of artifacts, and the three original occupations are palimpsests. There is no unequivocal association between evidence of human activity and megafaunal remains. © 2006 Wiley Periodicals, Inc.