Stable Isotopes from Marine Shells, Ancient Environments, and Human Subsistence on Middle Holocene Santa Rosa Island, California, USA

摘要

We report the analysis of stable isotopes on a suite of marine and estuarine shellfish, along with faunal data, from a Middle Holocene red abalone midden (CA-SRI-191) on Santa Rosa Island, California. Our research suggests that people harvested red abalones, mussels, and estuarine shellfish at about 6000 cal BP. Later in time around 4300 cal BP, people relied on California mussel and sea urchin with only trace amounts of red abalone and no estuarine taxa. Analyses of stable oxygen isotopes from California mussel, red and black abalone, and Venus clam shells indicate that a significant change in sea surface temperatures (SST; 2°C) between the two occupations is the primary cause for this discrepancy. Differences between the isotopic values of California mussel and black and red abalone shells from the same strata also suggest that people were probably diving in fairly shallow waters for red abalone rather than obtaining them from the intertidal zone. Our research and other studies in the region suggest that environmental and cultural variables (e.g., human harvest pressure) may have worked together to cause changes in the composition of local shellfish habitats. These data demonstrate the importance of conducting stable isotope analysis on a variety of different shellfish species (e.g., rocky coast, estuarine, and other taxa) in concert with traditional midden analysis to help understand ancient environmental, biological, and cultural developments in coastal, island, and other aquatic settings.