Spatio-temporal demographic dynamics of the human populations from Northwest Patagonia and central Chile during the Pleistocene-Holocene

Abstract

Our goal is to study the spatio-temporal changes in human demographic density in Northwest Patagonia and central Chile throughout the Late Pleistocene-Holocene using geo-referenced absolute dates. Given the heterogeneous environmental and cultural characteristics of this region, differences in the demographic dynamics across geographic areas are expected. Using 1,284 absolute dates we explored different null and continuous piecewise linear (CPL) models of regional population change. We also estimated density curves along with a local geometric growth rate analysis. The best fit model was a flexible CPL model, showing an initial increase in population density between ca. 15,500–12,500 years BP, a second rise after 6,500 years BP and a third increase after 2,500 years BP, although disparate spatio-temporal changes in the relative density were found. These results were robust when the effect of potential biases was considered –e.g., dates with large errors, marine-reservoir and old-wood effects– and the frequency distribution of absolute dates and sites were estimated. We observed significant spatio-temporal changes in human population density, which might be related to the complex environmental and cultural changes: the megafaunal extinction, the incorporation of marine resources and the acquisition of techniques for cultivating and processing food. The results of this study remark that, compared to other types of data, the use of absolute dates allows paleo-demographic reconstructions at regional geographical scales with higher spatial and temporal resolution.