Radical Diffusion vs Organic Innovation: A Bayesian Phylogenetic Approach to Acheulean Technological Transmission and Hominin Dispersal Demographics in Pleistocene Africa

The Acheulean technocomplex, characterized by its distinct handaxes and cleavers, represents an integral technological adoption spanning over 1.5 million years across Africa. Its persistence yet variable adoption raises critical questions about the mechanisms of technological transmission and its effect on innovation, cultural practice and hominin behavioral adaptability. A central debate revolves around whether major Acheulean technological shifts resulted from radical diffusion—rapid cultural transmission linked to demic expansions and social learning—or organic innovation—a more gradual, localized process of cumulative technological refinement. Resolving this debate is essential for understanding the levers of Pleistocene hominin cultural evolution and mapping its trajectory more definitively. This paper applies Bayesian phylogenetic methods, a computational framework originally developed in evolutionary biology, to model the branching patterns of Acheulean technological traits across Pleistocene Africa. By treating lithic assemblages as cultural lineages, one can reconstruct ancestral states, estimate rates of change, and test for signatures of punctuated diffusion versus gradual innovation. Our primary objectives are to quantify the phylogenetic signal in Acheulean tool morphology, evaluate whether technological shifts correlate with known hominin dispersals or environmental changes, and assess the relative contributions of demography and social learning to observed patterns. The successful integration of phylogenetic, spatial, and environmental analytical approaches in this study provides a novel, robust framework for interpreting patterns in the Paleolithic record. This methodological synthesis moves beyond traditional typological approaches, offering instead a dynamic, process-oriented understanding of technological change that accounts for both the remarkable stability and sudden transformations characteristic of the Acheulean record.