What shapes shape? Extinctions as a key driver of Acheulean cultural variation

This article explores Acheulean handaxe variation worldwide through integration of known patterns of hominin biogeography with a geometric morphometric analysis of handaxe shape.Previous research has documented clear differences in handaxe shape between continental regions, but the mechanisms by which these patterns appeared have been dramatically underexplored.This paper illustrates how the worldwide distribution of handaxe shape can only be understood through the lens of repeated dispersal and differential exposure to climatic-driven extinction risk in different regions of the Acheulean world.The paper is the first shape-based analysis of handaxe shape using specimens across its entire latitudinal range, to explore how population instability is reflected in discontinuity of handaxe forms in those regions, especially in Northern Africa and northwestern Europe.This is combined with an examination of the factors that govern investment in artefactual symmetry and thinning, even when functionally unnecessary, to explore how regional continuity and social network formation are reflected in the toolkit.These findings have important implications for how we consider human movement over the last million years, and the conditions under which competition between different hominin lineages can be generated.