3D multiscale curvature analysis of tool edges as an indicator of cereal harvesting intensity

• Published in: Journal of archaeological science, reports reports, 2020-10, Vol.33, p.102523, Article 102523
• Main Authors: Macdonald, Danielle A., Bartkowiak, Tomasz, Stemp, W. James
• Format: Article
• Language: English
• Subjects: Areal edge curvature; Edge angle measurements; Focus variation microscopy; Harvesting tools; Microliths; Surface metrology
• ISSN: 2352-409X
• DOI: 10.1016/j.jasrep.2020.102523

•Focus variation microscopy used to measure edge angles on stone tools.•Results indicate the edges appear “smoother” at the largest scale of calculation.•Edge shows more detail and appears “rougher” as scale of calculation decreases.•Maximal edge curvature proved reliable at documenting stone tool edges.•Maximal edge curvature on stone tool edges increased with increased use duration. The adoption of an agricultural lifeway is considered one of the most significant cultural events in prehistory. Microwear analysis of stone harvesting tools is among the many approaches used to document the transition to agriculture in the Near East. Traditionally, these microwear analyses rely on the use of optical microscopy and visual-verbal descriptions of wear criteria. In addition to traditional optical microscopy, ongoing research into the applications of surface metrology for the characterization of microwear traces has contributed to the development of quantitative microwear methods. Despite significant research into the quantification of lithic microwear polishes, there has been comparatively little research on the quantification of tool edge angles to understand function. In this paper, we test a new method for the quantification of areal curvature of stone harvesting tool edges at multiple scales using data collected with focus variation microscopy. These calculations are based on curvature tensors of the measured surface topographies along tool edge cross sections. This method allows calculation of maximal and minimal curvatures at each location and scale. For this paper, we analyze a set of experimental microliths used as cereal harvesting tools using changes in multiscalar areal edge curvature to mathematically document harvesting intensity (duration of use). This experimental research presents a new method for documenting used stone tool edges that will contribute to our understanding of how harvesting tools were used, curated, and discarded in the past, giving insight into the food collection practices of early farmers.