Why we're still arguing about the Pleistocene occupation of the Americas

Although empirical issues surround the when, how, and who questions of New World colonization, much of current debate hinges on theoretical problems because it has become clear that our understanding of New World colonization is not resolute. In fact, the central issues of debate have remained essentially unchanged for the last eighty years. The now classic and probably incorrect story of New World colonization begins in Late Pleistocene Siberia, with small a population of foragers migrating across Beringia (similar to 13,500 calendar years before present (CYBP) (Box 1) through an ice-free corridor and traveling through the interior of North America. High mobility and rapid population growth spurred southward expansion into increasingly distant unoccupied regions, culminating in the settlement of the Southern Cone of South America. Armed with the skills and weapons needed to maintain a megafauna-based subsistence strategy, early colonists necessarily had the adaptive flexibility to colonize a diverse array of Pleistocene landscapes. For a time, this scenario seemed well substantiated. The earliest sites in South America were younger than their northern counterparts, fluted artifacts were found across the Americas within a brief temporal window, and projectile points capable of wounding elephant-sized prey were commonly found in association with proboscidean remains. The Bering Land Bridge connecting Asia to Alaska and an ice-free corridor providing passage between the Pleistocene ice masses of Canada seemed to provide a clear route of entry for Clovis colonists. However, recent archeological, paleoenvironmental, biological, and theoretical work largely questions the plausibility of these events.