Late Holocene Subsistence Change and Marine Productivity on Western Santa Rosa Island, Alta California

Institutionalized differences in social status developed on California's northern Channel Islands from the Late Middle (A.D. 650-1150) to Late (A.D. 1300-1782) periods. This is associated with the proliferation of sedentary communities along the coasts of these islands and a number of important socioeconomic changes, including a greater emphasis on fishing and the production of non-food craft items. These changes were particularly rapid during the Middle to Late Period Transition (MLT; A.D. 1150-1300) and partly attributed to significant environmental change during this interval. Population-resource imbalances caused by decreased marine productivity, drought, or some combination of the two have been suggested as possible environmental triggers for the sociopolitical changes evident in the archaeological record at this time. Shell midden deposits at CA-SRI-15 provide a unique opportunity to test whether elevated sea surface temperature (SST) reduced marine productivity during the MLT and contributed to these population resource imbalances. This is because the site was occupied relatively continuously from the Late Middle Period through the Late Period. Faunal records and associated oxygen isotopic data from the site do not support the hypothesis that increased SST reduced marine productivity during the MLT.