Fat composition and Nunamiut decision-making: a new look at the marrow and bone grease indices

In his study of marrow procurement, Binford [L.R. Binford, Nunamiut Ethnoarchaeology, Academic Press, New York, 1978] stressed the prevalence of oleic acid, an unsaturated fatty acid, over marrow quantity and processing time for explaining Nunamiut selection of caribou bones. He also stressed the importance of oleic acid in selection of bones for grease rendering. Jones and Metcalfe [K.T. Jones, D. Metcalfe, Bare bones archaeology: bone marrow indices and efficiency, Journal of Archaeological Science 15 (1988) 415–423] and Brink [J.W. Brink, Fat content in leg bones of Bison bison, and applications to archaeology, Journal of Archaeological Science 24 (1997) 259–274] disputed the importance of oleic acid in these activities. This debate is reevaluated in this paper.Reexamination of the relationship between quantity of marrow in caribou bones and skeletal parts selected for marrow procurement reveals two linear clusters instead of one. Two linear clusters are also identified in the relationship between bone grease weight and skeletal parts collected for grease rendering. Bones that are selected more often than expected in these correlations are precisely those that are rich in oleic acid. Although the proportions of skeletal parts selected for marrow procurement are strongly correlated with marrow quantity, a stronger correlation was found with quantity of unsaturated fatty acids. The latter variable constitutes the basis of the Unsaturated Marrow Index, a new scale of marrow utility introduced here.