Flake scar density and handaxe reduction intensity

Abstract

Quantifying biface reduction is an important goal in Palaeolithic archaeology for determining the length of reduction sequences, and to contextualise interpretations of biface morphology. In particular there is contention as to whether or not Acheulean handaxes were resharpened. Here we test the flake scar density index (SDI), calculated using 3D laser scans of bifaces, as a measure of handaxe reduction. We experimentally reduced an assemblage of 57 handaxes tracking changes in their SDI and mass lost at each stage of reduction. We tested the effects of blank type, coarseness of the stone, and different protocols for reduction. Our results show that the SDI is indeed an effective measure of mass lost, although it is influenced by the blank type of the handaxe.We applied the SDI to two archaeological assemblages of Acheulean bifaces from East Africa: Kariandusi and Isenya; and two archaeological assemblages from India: Patpara and Bhimbetka. Exotic materials were more reduced at Kariandusi and Isenya. A relationship between SDI and volume, such that smaller handaxes have higher scar densities, and are thus likely small because they have been reduced more, suggests resharpening. Conversely, the lack of such a relationship may be taken as evidence that bifaces were not resharpened. Our results show that exotic handaxes from Kariandusi, local handaxes from Isenya, and bifaces in general from Patpara were resharpened. On the other hand neither local handaxes from Kariandusi, cleavers from Isenya, nor cleavers from Bhimbetka, were resharpened. The unretouched bit formed by the termination of the original flake blank on the Isenya and Bhimbetka cleavers provides independent evidence for the lack of resharpening.