A substantial amount of archaeological data suggests groups with markedly different lithic technologies and subsistence adaptations were widespread throughout both American continents by ∼13–13.5 ka. While there are fewer archaeological sites credibly dated to ∼13.5–15.5 ka, they are sufficient to indicate human foragers occupied at least the Pacific coasts of both continents and probably interior continental locations as well. Assuming it required at least 500–2000 years for initial populations to expand throughout these regions, the first colonists must have begun to spread throughout the Americas south of the Laurentide and Cordilleran ice sheets well before post-glacial global warming at 14.5 ka resulted in the melting of the ice sheets and a rapid rise in sea levels. The European and Asian gateway regions to the Americas were occupied by ∼35 ka, and the initial colonization likely post-dates this interval. Genetic data suggest the first colonists derive from populations that occupied the Altai Mountains area of central Asia sometime before ∼24 ka, but this hypothesis is based on the modern distribution of haplogroups, and the locations of their ancestral populations at the time they diverged from parent Eurasian populations is unknown. The Altai region is equidistant from both the Atlantic and Pacific gateways to the Americas, and the direction from which the first Americans arrived is a matter of speculation. There are no empirical data supporting the genetic-based hypothesis that there was a population “standstill” in interior Beringia for thousands of years. If there was such a standstill, it more likely occurred in coastal refugia or in other areas in northeast Asia. Scattered data suggest the possibility the Americas were initially occupied sometime prior to ∼17 ka, but these need to be confirmed before they are widely accepted. Of the three most viable hypotheses for the peopling of the Americas, a Clovis First – Ice-free Corridor model appears to be dead and buried; an Atlantic Ice Shelf – Solutrean Origin model is untested, with no empirical data either supporting or falsifying the model; a Pacific coastal model may be the most viable explanation for the initial peopling of the Americas, but also has limited empirical support. This model suggests that boat-using foragers, with an adaptation to the shorelines and estuaries of the Pacific Rim, moved around the margins of the northern Pacific into North and South America before expanding into interior continental regions. Such a migration likely occurred during or prior to the last full glacial.
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