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Changes in social organization accelerated on California's northern Channel Islands beginning around 1300 cal BP. These changes were associated with shifts in settlement and subsistence patterns related in part to drought conditions during the Medieval Climatic Anomaly (MCA; 1150-600 cal BP). By the end of the MCA, settlement patterns demonstrate evidence for territoriality and can be described by the ideal despotic distribution. The occupants of the most productive habitats prevented new settlers from moving in and accessing the available resources. We use faunal data from five sites on western Santa Rosa Island (CA-SRI-15, -31, −97, −313, and −333) to trace changes in settlement and population aggregation through this period. Fishing, which can support higher population densities than harvesting shellfish, increased overall from the Middle (2550-800 cal BP) to Late Period (650-168 cal BP), but there were fewer settlement sites on western Santa Rosa Island. In the centuries before the Middle to Late Period Transition (MLT; 800-650 cal BP), people occupied sites geographically dispersed along the west coast of the island. After the MLT, fishing was restricted to fewer large coastal villages. We argue that environmental stress and an increase in warfare on the northern Channel Islands drove the growth of more permanent consolidated villages, the development of territoriality, and settlement patterns consistent with greater resource defense and therefore a more despotic distribution.

Point Bennett, on western San Miguel Island, California, was an important location for sea mammal hunting through time. We use stable oxygen isotopic (δ18O) measurements from California mussel (Mytilus californianus) shells to reconstruct a seasonal pattern of mussel harvesting by the human occupants of Point Bennett during three time intervals dated to the middle (~7,550 – 3,600 cal B.P.; CA-SMI-528, Stratum 3) and late (after ~3,600 cal B.P.; CA‑SMI-528, Stratum 1; CASMI-602) Holocene. During both periods of occupation at CA-SMI-528, mussel harvesting was primarily during thespring, coincident with onshore sea mammal breeding. This suggests a seasonal pattern of site occupation. At CA-SMI-602, mussel harvesting primarily occurred during the summer and fall. This is opposite when sea mammals are present in highest densities, suggesting year-round occupation. This shows how seasonality of mussel harvesting can be used alongside other indicators like seasonal availability of sea mammals to understand broader patterns of human mobility.

Using targeted survey, excavation, and radiocarbon dating, we assess the extent to which human settlement patterns on California’s northern Channel Islands fit predictions arising from the ideal free distribution (IFD): (1) people first established and expanded permanent settlements in the regions ranked high for environmental resource suitability; (2) as population grew, they settled in progressively lower ranked habitats; and (3) changes in the archaeological record associated with high population levels such as increases in faunal diversity and evenness in high-ranked habitats are coinci- dent with the expansion to other areas. On Santa Rosa Island, the early permanent settlements were located in both high- and middle-ranked locations, with the most extensive settlement at the highest ranked locations and only isolated sites elsewhere. Settlement at a low-ranked habitat was confined to the late Holocene (after 3600 cal BP). Drought influenced the relative rank of different locations, which is an example of climate adding a temporal dimension to the model that episodically stimulated popu- lation movement and habitat abandonment. Because the IFD includes a wide range of cultural and environmental variables, it has the potential to be a central model for guiding archaeological analysis and targeted field research.