The Skills of Handaxe Making: Quantifying and Explaining Variability in 3D Sinuosity and Bifacial Asymmetry

Abstract Observations about handaxe techno-morphology, like their symmetry, refinement, and fine edges have long been used to reconstruct the evolution of hominin cognition, skills, and technological decision making. However, these interpretations about the cognitive and technical abilities of Acheulean hominins often rely on the most ‘beautiful’ or supposedly ‘archetypical’ looking handaxes. But how often do these finely made handaxes actually occur in assemblages and how can we identify handaxes that were more skillfully made than others? Instead of seeking to estimate the skill level of individual past knappers, a trait that is oftentimes obscured in the archaeological record, we approach the question of knapping skill from the other direction. We instead ask how much skill was required to manufacture a handaxe? We explore, not the skill level of a handaxe’s maker, but how skillfully an individual handaxe was made. We put forth a suite of novel 3D methods of handaxe analysis for calculating their 3D edge sinuosity and 3D asymmetry. Using these methods, we quantify traits that are difficult to achieve during handaxe-making, providing an estimate of the requisite amount of ability, experience, attention, and effort demanded by their manufacture. Among our large sample of handaxes from the later Acheulean of the southern Levant, we find that blank size and tool-/site-use best explain the presence of more skillfully-made handaxes. Handaxes made on larger original blanks appear to afford more volume with which to enact longer and more skillfully demanding reduction sequences. Moreover, handaxes occurring at more recurrently occupied sites demanded less skill investment and appear geared towards the more expedient fulfilment of quotidian tasks. In the later Acheulean of the southern Levant there appears to be a great diversity in how skillfully handaxes were made, likely reflecting a diversity in the goals of handaxe making.