An experimental assessment of the influences on edge damage to lithic artifacts: A consideration of edge angle, substrate grain size, raw material properties, and exposed face

Functional analyses of stone tool assemblages face a number of methodological challenges. Aside from determining specific uses, it can be difficult to know which artifacts in an assemblage were used at all. Typically retouch is taken as a proxy for indicating past use, but ignoring unretouched flakes means excluding the overwhelming majority of most assemblages. Assessing whether an unretouched flake has been used is complicated. Edge damage on flakes can be caused by use or by taphonomic processes. One of the more important of these processes is trampling. Experiments have shown that trampling can create damage mimicking retouch, and unlike some other taphonomic processes trampling is otherwise difficult to detect. One possible solution is to look for patterning in the placement (left vs. right, ventral vs. dorsal, proximal vs. distal) of edge damage, and recent studies using GIS based approaches have shown the utility of this method at an assemblage level. Here we trampled a set of experimental flakes made from two raw materials on two substrate types and analyzed the edge damage patterns using a newly developed image analysis program that is similar to previous GIS based approaches. We found that a previously unquantified variable, edge angle, is strongly correlated with the likelihood of damage. Thus in circumstances where edge angles are non-randomly distributed across flake types, trampling damage will be patterned. These results have implications for previously published edge damage studies, and further indicate that basic flake mechanics need to be considered in studies where function is inferred from edge damage patterns. Approaches to the archaeological record that employs assemblage level assessments of edge damage, must consider a range of factors when inferring behaviors from these patterns.