Seasonal stability in Late Holocene shellfish harvesting on the central California coast

Oxygen isotope determinations from 92 California mussel (Mytilus californianus) shells from ten archaeological sites in central coastal California show relatively stable seasonal harvesting patterns between 3600 CAL BP and historic contact (AD 1769). Coastal occupants harvested mussels nearly year-round and seem to have occupied individual residential bases throughout the seasonal cycle. Interior groups returned with mussels from the coast mostly in the spring and early summer, but almost never in the late summer/early fall when nut crops were harvested. These findings suggest two inter-dependent groups with distinct seasonal settlement strategies: inland people, reliant on acorns and other nut crops harvested in the fall, and coastal inhabitants who were less involved with acorns. This pattern is supported by accounts recorded by the first Spanish explorers in AD 1769. While some interior groups may have been seasonally migrating “collectors,” coastal populations were less mobile, inhabiting individual residential sites throughout the year, albeit not necessarily on a permanent basis. These findings highlight the strong influence of coastal environments and resources on hunter-gatherer mobility.