Climate influence on the early human occupation of South America during the late Pleistocene

The settlement of South America marks one of the final steps in human expansion. This study examines the impact of climate change on this process, focusing on two millennial-scale climatic phases—the Antarctic Cold Reversal and Younger Dryas. Using Bayesian chronological modelling, a cultural timeline was constructed from approximately 150 archaeological sites and 1700 dates, and compared against paleoclimatic records. Findings suggested that human activity likely began in regions most affected by the Antarctic Cold Reversal, specifically in southernmost and high-altitude areas. Together with estimates indicating that the onset of megafaunal exploitation and bifacial point technology occurred before or during the Antarctic Cold Reversal, results suggested that cold conditions did not likely hinder human settlement. Key factors likely included accumulated cultural adaptation and relatively milder climatic changes in the Southern Hemisphere. More widespread occupation likely occurred during or, more likely, after the Younger Dryas as conditions stabilised. Results highlighted the western Andes as a crucial dispersal route and questioned the role of humans and climatic shifts on megafaunal extinctions. An analysis of the compiled archaeo-chronometric dataset revealed significant underrepresentation and reporting gaps, highlighting the need for expanded research and rigorous documentation to improve the reliability of the cultural timeline.