A Synthesis of African Paleoclimate from 150-35ka and Possible Implications for Middle Stone Age Archaeology

We have developed a synthesis of African paleoclimate data covering the period vital to the origin of Modern Humans and their expansion out of Africa. Discrete and continuous data from over 50 sources, including both terrestrial and marine records, are used to interpret climate change on a continental scale and to identify regions with coherent patterns of aridity and temperature. We infer regional differences in broad climatic histories based on many climate indicators: lake level histories, magnetic susceptibility, pollen, dust, speleothem growth, and dune migration. All of the records compiled in this study are radiometrically anchored in time. We divided the continent into four climatic regions (1) North Africa, (2) the Sahel, (3) the Afrotropics, and (4) South Africa. We interpret regional differences in climate to result from changing global atmospheric circulation patterns including the location of the ITCZ. Circum-African sea surface temperature data are consistent and warm during the tropical belt megadrought period from ~105-90ka. This suggests that changes in the delivery mechanism of moisture to specific regions are responsible for the extreme aridity, and not the amount of moisture available to the entire continent from the surrounding oceans.

We explore the extent to which these environmental changes provided the context for behavioral innovations seen in Middle Stone Age archaeological sites, perhaps through demographic shifts among early populations of Homo sapiens that included local increases in relative population pressure. Several archaeological indicators suggest behavioral change as a possible response to increased risk due to local environmental degradation. These include novel hunting technology, a broadened resource base, and early suggestions of social networks, the timing and relative abundance of which is assessed through a composite database of radiometrically dated archaeological assemblages.