The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Evidence for the peopling of South America: archeological and genetic perspectives


Department of Biology, Stanford University

March 26, 2015 , Gateway Ballroom 2 Add to calendar

As the last major continent colonized by humans and the stage for a Late Pleistocene megafaunal extinction event, a firm understanding of the peopling of South America is of clear importance, yet has received comparably little attention. To address this deficit, we compiled a new dataset of 900+ published radiocarbon dates older than 8,000 years before present. Our dataset has been re-calibrated using the ShCal13 curve (probability ≥ 95%) and includes 200+ unique archeological sites spanning the continent. We jointly analyze these data with published genome-wide SNP data from 30 South American indigenous populations (Reich et al. 2012, Nature). Methods are implemented using the R package spatstat and ArcGIS. To describe movements on a broad scale, we evaluate the density and direction of spread of archeological dates over time. Surprisingly, the earliest known sites appear concurrently throughout the continent, rather than a north-south progression along the western coast. Considering water routes, elevation, and terrain ruggedness, we compare least-cost pathway migration route estimates based on archaeological data to those inferred from genetic data. While we find support for previous assertions of a coastal migration, there are clear biases due to sampling, excavation, and preservation. We emphasize analyses demonstrating a need for increased excavation in specific geographic regions, and at lower levels of known sites. This work creates a novel framework that incorporates two distinct types of data to make demographic inferences about the initial colonization of South America, and acts as a resource for future archeological studies on the continent.