THE PALEOINDIAN COASTAL ENTRY HYPOTHESIS: A VIEW FROM THE COLUMBIA PLATEAU, WASHINGTON STATE

The “Clovis first” and “Ice Free Corridor” models of initial human colonization of the Americas fail to accommodate the earliest (Pre-11,000BP) Paleoindian archaeological sites. As a result the Coastal Entry Hypothesis has recently gained rapid support among Paleoindian specialists. While the details of coastal entry are sparse due to an inundated Pleistocene coastline and low visibility of the earliest sites, the unequivocal fact remains that at some point in time the first Americans left the coast and entered the continental interior. The most parsimonious explanation for interior colonization from the coast would have colonizers moving through natural travel corridors such as the Columbia River valley. Given its location relative to receding continental glaciers, models of initial human colonization along the Pacific coast should consider the Columbia River corridor as a viable and likely initial pathway to the continental interior. Geoarchaeological research at newly discovered sites supports this hypothesis and clearly demonstrates that Upper Pleistocene people exploited ecological zones of high productivity in Scabland tracts of the Columbia Plateau. Along the Columbia River corridor a generalized lack of Upper Pleistocene floodplain development by and large precluded deposition and preservation of Pleistocene archaeological sites; subsequent catastrophic flooding likely destroyed any such evidence. To the contrary, upland sites in Scabland tracts are well preserved and available to test hypotheses of initial colonization. Geomorphic and hydrogeologic features that are correlated with the earliest archaeological sites on the Columbia Plateau include (1) catastrophic fluvial deposits adjacent to scoured and denuded bedrock; (2) extinct paleolakes, marshes and remnant landforms associated with high stands of these bodies of water; and (3) alluvial terraces within scabland flood channels which formed as the result of post-flood dewatering and subsequent upper Pleistocene alluviation. By expanding research into the geologic and ecologic context of the Cordilleran interior it is possible to hypothesize how Pleistocene colonizers made the transition from marine to terrestrial adapted life ways. This analysis of Columbia Plateau geoarchaeology is an example of such research.