In the knapper's hands : testing markers of laterality in hominin lithic production, with reference to the common substrate of language and handedness

Right-handedness is one of humankind's distinguishing features, but its origins are obscure. The archaeological record of non-Homo sapiens sapiens species provides evidence for bimanually coordinated hand-use patterns in the form of lateralised skeletons, use-wear on tools, and stone knapping. The underlying biomechanical assumptions of these were subjected to analytical validation using ethnographic parallels, biomechanics, and experimental data. The evidence shows robust handedness from Acheulean times onward, leaving a large gap in the dataset for more ancient hominin species. This dissertation explores in detail the handedness markers from lithic production, with a focus on the earliest hominin technology in order to bridge this gap. Knapping experiments were undertaken on three potential markers which could represent the earliest evidence for handedness: single-platform core rotation, large flake production, and tranchet flake production. A new methodology was created for tranchet flaking and was applied to a sample of 451 handaxes from the British Lower Palaeolithic site of Boxgrove, UK. A statistically significant bias toward left-struck tranchet negatives and flakes was found at Boxgrove. However, the experiments showed that knapping a coup du tranchet is not subject to biomechanical constraints relating to handedness. Similarly, the assumptions underlying the single-platform core rotation did not withstand experimental validation. The leftward tranchet preference at Boxgrove is interpreted as resulting from the well-established motor habits of skilled knappers. The possible connection between bimanually coordinated hand-use patterns and bi-hemispheric language is examined in a critical assessment of theories about the common substrate. A new model for the common substrate is proposed, based on the conceptual nature of the complementary roles of both sides, in which handedness and language are characterised by functional role differentiation.