Impact Scar Frequency, Bone Density And Marrow Utility: An Experimental Study

This paper presents an experiment designed to evaluate the relationships between impact scar, bone density and the marrow utility of various appendicular elements. Several North American bison assemblages show positive correlations between impact scar frequencies and by-element marrow utilities. However, this pattern may represent an equifinal relationship between bone density, nutritional utility and processing effort. In our experiment, we test the hypothesis that this pattern is a function of bone density; elements documenting higher frequencies of impacts will be more robust and require more effort to open, without regard for nutritional utility. To do so, we build a device designed to impact and open bison long bones in a controlled manner by dropping a large steel ball onto bison limb bones. Our experiment recorded both the numbers of impacts needed to open the marrow cavities and the associated marrow weights of 274 bison limb elements. Our results indicate that the lowest utility elements require the most effort to open and the high-utility elements the least. These results suggest that impact frequencies may be read as signalling nutritionally motivated processing efforts.