Investigating the Angle of Tool Impact on Bone and Resin Surfaces

This project presents a modified and validated version of the Angle of Tool Impact (ATI) formula and method developed by Bello et al. (2009). This method can be used to determine the angle at which a tool has impacted the bone when producing a cutmark, offering behavioural insight when used as part of a multivariate approach. Fresh and dry pig ribs, and a resin substrate, were cut at three different angles (45°, 60°, 90°) using replica Middle Neolithic flint knives and a stainless-steel kitchen knife. Cutmarks were analysed using a 3D digital microscope to obtain cross-sectional profile measurements which were used in conjunction with the modified ATI. Results showed a clear indication of a cutmark produced at either an acute angle (45° or 60°), or perpendicular to the surface (90°). Differences between bone freshness and tool material had minimal effect and resin effectively replicated cut mark angles. However, unobserved variables had a noticeable influence on some results, as observed within the statistical analysis. Overall, the modified version improves upon the original by validating ATI measurements against known produced angles and by applying averaged cross-sectional profiles to reduced morphological anomalies and user-related errors. Bello, S. M., Parfitt, S. A. and Stringer, C., 2009. Quantitative micromorphological analyses of cut marks produced by ancient and modern handaxes. Journal of Archaeological Science, 36 (9), 1869–1880.