Expanding Archaeological Approaches to Ground Stone: Modeling Manufacturing Costs, Analyzing Absorbed Organic Residues, and Exploring Social Dimensions of Milling Tools

Abstract

Although ground stone artifacts comprise a substantial portion of the archaeological record, their use as an important source of information about the past has remained underdeveloped. This is especially true for milling tools (mortars, pestles, grinding slabs and handstones) used by hunter-gatherers. Three studies that apply novel techniques and approaches to prehistoric milling technology are presented here. Together they demonstrate that substantial opportunities exist for new avenues of inquiry in the study of these artifacts. The first combines a simple optimization model from behavioral ecology with experimental data to weigh manufacturing costs against gains in grinding efficiency for mobile hunter-gatherers. Results run counter to widespread assumptions that mobile hunter-gatherers should not spend time shaping grinding surfaces on milling tools. Next, gas chromatography-mass spectrometry (GC-MS) is used to analyze lipid preservation in modified rock features in dry caves at Gila Cliff Dwellings National Monument, New Mexico. A high concentration of lipids, derived from processing a seed resource, was recovered from a grinding surface in these caves. The lipid content in this surface is comparable to amounts recovered from select pottery sherds that have been used for radiocarbon dating. The third study uses synchronic and diachronic variability in morphology, use-wear, and symbolic content to analyze ground stone milling tools from mortuary contexts in the San Francisco Bay Area of California. Archaeological and ethnographic evidence supports the inferred association of certain mortars with feasting and ritual activities. Differences in the representation of some of these forms in male and female graves may reflect changes in the roles of women and men in community ritual and politics.