A GIS based approach to long bone breakage patterns derived from marrow extraction.

Abstract

In archaeological assemblages the presence of percussion marks, on the surface of long bones, is an indicator of long bone marrow extraction. The form, quantity and distribution of percussion marks are analysed to gain a better understanding of the marrow extraction process. Patterns of bone percussion damage in archaeological assemblages may highlight standardized actions, possibly related to butchery traditions. However, additional factors could underlie these patterns and should also be considered. In this article we test intuitiveness as a factor in appearance of percussion mark patterns, to see if patterns can appear when bones are being fractured without prior experience with bone fracture properties. To test this hypothesis, for this study we selected a sample of 40 cattle (Bos taurus) long limb bones from a large bone breakage experiment (400 long limb bones), where participants had no previous experience in bone breakage and may thus have broken bones intuitively. We used Geographic Information System (GIS) software to analyse the distribution of percussion marks. Using ArcGIS Spatial Analysts tools, we identified and quantified significant concentrations of percussion marks. Results show that percussion mark patterns emerge for the same bone element, and that specific sides and zones were recurrently selected by experimenters. The distribution of patterns varies among the different long bone elements, and we attribute this variance to an adjustment to bone morphology. In addition, we calculated and identified bone damage patterns resulting from hammerstone percussion. Crossing bone survivorship with percussion mark patterns enabled us to recognise and evaluate the effects of fragmentation and surface visibility in controlled experimental conditions. The GIS method facilitates comparisons between different variables and provides a sophisticated visual representation of results. Enlarging the sample will allow to constitute a more substantial analogous model for fossil assemblages.