Weighing vs. Counting: Measurement Reliability and the California School of Midden Analysis

The California School of Midden Analysis represents a long-standing tradition of using weight, rather than minimum number of individuals (MNI), to analyze shell recovered from archaeological sites in California. This method originated at the University of California, Berkeley, in the early twentieth century and continues to the present, in spite of the advent of counting measures such as MNI and NISP (number of identified specimens) in faunal studies. We argue that MNI estimates are more reliable than weight as a measure of taxonomic abundance for most research issues being addressed with California shell data. Examples using both weight and MNI measures for shell from California coastal sites produced divergent results. This disparity shows that weight measures produce potentially misleading interpretations regarding the importance of marine habitats exploited and the diet of the site’s occupants.