Assessing the ability of the LAMAP predictive model to locate hunter-gatherer sites: An Alaskan case study

Evidence from archaeological sites and ancient and modern DNA suggests that people first entered northern North America via Beringia no later than 15,000 years ago, and potentially as early as 24,000 years ago. When people moved south to colonize the rest of the American continents is still debated. The presence of ice sheets means that two routes were the most likely: down the unglaciated coast of the Pacific Northwest, and/or via an interior route characterized as the ice-free corridor. Large areas of Late Pleistocene land on the coast were submerged when sea levels rose at the beginning of the Holocene, around 10,000 years ago, making it difficult to locate potentially early sites. There is now a need to develop and test methods that identify high potential locations for finding sites on those now-submerged landscapes. The LAMAP method (Carleton et al. 2012) has been successful in predicting areas of high archaeological potential associated with permanently occupied settlements of agrarian societies. This study is the first application of LAMAP to mobile hunter-gatherer sites. A study area was defined in the Tanana Valley, Alaska, and the location and age of known archaeological sites was sourced from files in the Alaska Heritage Resources Survey database. The location of each site was plotted on a raster map produced in QGIS using six Digital Elevation Models accessed from the USGS's National Elevation Dataset. This provided information relating to six physical variables for each site: Elevation, Slope, Aspect, Distance to Drainage, Viewshed and Convexity. The study area was divided into more than 700 million cells. LAMAP calculates the similarity of each cell to the cells found in a 1-km sample area around each known site. Mapping the distribution of similarity indices created a map of archaeological potential. We ran LAMAP on 91 randomly selected site locations to create a map of archaeological potential, and tested it by examining the location of the second set of 91 sites from the study area. Areas of high archaeological potential contained more of the second set of sites, confirming LAMAP's ability to predict high potential areas for mobile hunter-gatherer sites. A second analysis, using pre and post 10,000 cal BP sites, showed the same results, demonstrating that long-standing physical features of the landscape are robust predictors of high potential areas, regardless of the time period. LAMAP is one of a number of methods for modelling high potential areas, each of which has advantages and disadvantages, for the preliminary exploration of now-submerged terrestrial landscapes.