Middle and late Holocene hunter-gatherer adaptations to coastal ecosystems along the southern San Simeon Reef, California

This research examines prehistoric coastal adaptations over a 5,000- year interval during the Middle to Late Holocene along the southern San Simeon Reef, San Luis Obispo County, California. I integrate survey, site excavation, biological, and paleoenvironmental data to determine how cultural and environmental factors affected subsistence and settlement patterns. Interpretations focus on rocky littoral ecosystems and the adaptive strategies of maritime hunting, fishing, and gathering.During the Middle Holocene, mobile groups exploited high ranked, diverse, and dense resources such as red abalone. Temporally discrete red abalone middens are an example of specialized adaptations. By the Late Holocene, southern San Simeon Reef populations responded to climate-driven resource stress by intensifying existing subsistence strategies through technological innovation and resource intensification. This is evidenced by an overall expansion of diet breadth, increased emphasis on fishing, a shift to lower-ranked land mammals, and increased dependency on resources with higher search and handling costs. A transition to intensified fishing suggests a change in social organization, with collective groups engaged in procurement, processing, storage, and fishing gear manufacture and maintenance activities.Although subsistence intensification occurred over time, population density remained low and dispersed across the region. Based on shellfish assemblages, intertidal communities remained relatively stable, with only red abalone showing a decrease in size over time. A dietary focus on black turban snails, and the low frequency and small size of California mussel shells may be attributed to ecology rather than resource intensification.Middle/Late Transition and Late Period settlement was a fluid system, with populations occupying productive resource locations. Medieval Climatic Anomalies drought conditions appear to have transformed social organization, requiring trade or marriage networks to buffer climatic instability. As conditions deteriorated, rocky intertidal shellfish, similar to study site assemblages, appear in interior sites. Although it is uncertain how shellfish reached the interior, this pattern originated during severe droughts that undermined socio-economic systems. Southern San Simeon Reef settlement and subsistence systems clearly reflect the diversity of mobile subsistence adaptations in a coastal environment that requires greater emphasis on researching resource variability.