Acheulean variation and selection: does handaxe symmetry fit neutral expectations?

Abstract

It has been suggested that the property of symmetry observed in Acheulean handaxes was selected for functional, adaptive or social and aesthetic reasons. However, selectionist accounts of variation may be contrasted with the approach taken by population geneticists to molecular variation. Population geneticists always first assume a neutral pattern of variation for molecular data, and only look to non-neutral (e.g., selective) scenarios for pattern and variation in the face of strong evidence against this null model of neutral expectation. Here, using a combination of cultural transmission theory, morphometrics, and the principles of population genetics, (null) neutral expectations for Acheulean handaxe symmetry are tested. The results of the analyses are inconsistent with a null hypothesis of neutral expectation for patterns of handaxe symmetry variation. Rather, the results imply that the property of symmetry in Acheulean handaxes was subject to selection for functional, adaptive or social reasons.