The environmental context of the Middle-to-Late Stone Age Transition in eastern Africa: seasonality as a key factor

In the transition between the Middle Stone Age (MSA) and the Late Stone Age (LSA) in eastern Africa, the archaeological record shows a gradual and asynchronous decline in MSA features and an increase in LSA characteristics. A link between this pattern and climatic variations has not yet been tested in the region using lithic attribute analysis. To investigate that, we integrated technological data of blades and bladelets from eastern African contexts (Marine Isotope Stages 5-1) with large-scale paleoclimatic reconstructions. A principal component analysis (PCA) finds the first component (reflecting artifacts dimensions) significantly correlating with time. This highlights a progressive reduction in size over time, a trend that has already been suggested for the MSA-LSA transition. The second principal component reflects artifact shape and shows a significant correlation with the marked aridity of the dry season (a common proxy for seasonality in tropical regions), with higher specialization observed in more humid areas. Based on this, we propose a new model where more variable blades reflect greater versatility in foraging strategies as adaptation to environments that become more challenging during part of the year. On the other hand, when it rains more during the dry season and differences through the year are milder, a more specialized toolkit with thinner, longer elements would emerge from refining and adapting to uniform and predictable situations and challenges.