Middle Holocene residential mobility in western Santa Rosa Island, California

Abstract

The middle Holocene (8200-4200 cal BP) on California's northern Channel Islands (NCI) was a period of important population change, including the elaboration of settlement and subsistence systems during periods of environmental stress. On Santa Rosa Island (SRI), there is evidence for intensive settlement associated with greater sedentism along the relatively wet and productive northwest coast. We use faunal, chronological, and stable oxygen isotopic (δ18O) data from middle Holocene interior residential base sites to reconstruct patterns of mobility between the coast and the interior of the island. Most of the interior sites on SRI dating to this period are oriented toward the northwest coast and previous isotopic studies have indicated they were used seasonally to access terrestrial plant resources and fresh water from fog. This is supported by the faunal record from CA-SRI-50, which was occupied during the summer and fall and has a low-diversity faunal record associated with field processing prior to transporting marine foods to the site. CA-SRI-152 and -229, however, are two sites oriented toward the southwest coast, an area that is drier and less productive overall, but contained a high abundance of red abalone (Haliotis rufescens). These sites appear to have additional roles, including as stopover locations, reflected by a lower density but more diverse faunal record with settlement focused on the spring. This study indicates that the structure of interior residential bases on the NCI during the middle Holocene was not monolithic and that people traveled to the interior for different purposes. By understanding the diversity of sites in the context of environmental variability during the middle Holocene, we can better reconstruct patterns of seasonal mobility and site use during an important period of change that contributed to the eventual development of coastal hunter-gatherer-fisher social complexity.