Chronology of Red Abalone Middens on Santa Cruz Island, California, and Evidence for Subsistence and Settlement Change

Red abalone middens on Santa Cruz Island, California, are conspicuous because they contain the shells of red abalone, a large marine gastropod, even though mussel shells are the most abundant by weight. Recently obtained radiocarbon dates push back the time interval of the island's red abalone middens to ca. 6200 cal B.C., with the bulk of them dating between 5000 and 3300 cal B.C. Faunal remains from two sites indicate that subsistence on marine resources intensified at the onset of the time interval of the middens. In addition, beginning ca. 3900 cal B.C. the island settlement system became more complex and subsistence on marine resources, particularly with respect to marine mammals such as dolphins, once again became more intensive. Proposed explanations for the subsistence and settlement shift concern the development of possibly more complex watercraft and the adoption of the mortar and pestle for processing plant foods. The expanded time interval during which red abalone middens occur has revealed that cooler sea-surface temperature is only a partial explanation for their occurrence.