A multiproxy sediment-core record of lake-level change in paleolake Makgadikgadi (82–21 ka) with implications for human occupation

The Makgadikgadi Basin in central Botswana is a key region for understanding Stone Age archaeology and human evolution. However, paleoenvironmental reconstructions have so far offered only fragmentary insights into past hydroclimatic and environmental conditions. We present the first environmental record from Sowa Pan, paleolake Makgadikgadi, covering the last 82-20 ka (Marine Isotope Stages 5-2). Sedimentological and biomarker lipid analyses reveal four distinct lake phases, reflecting major hydrological shifts and sediment provenance. From 82 to 75 ka, the lake was shallow, with lowest lake levels temporally coinciding with Middle Stone Age archaeological material (silcrete lithics, mainly unifacial and bifacial points) on the western lakebed. Between 75 -58 ka, the lake refilled, likely fed by river inflow sourced from the Angolan highlands. A second low stand likely occurred around 58-56 ka. From 52 to 37 ka, geochemical proxies indicating a change in lake inflow with less influence of the Kwando catchment. During this time, the lake had high primary productivity and biomarkers for terrestrial herbivores are recorded in the sediments. After an accumulatory hiatus, the youngest unit (ca. 21 ka) marks the formation of the Sowa Spit, characterized by high sand input and minimal organic preservation. This record refines the chronology of lake-level changes and reveals that desiccation phases provided ecologically viable landscapes for human activity. It also identifies shifting sediment and nutrient sources that shaped lake dynamics during the late Pleistocene.