Putting Human Exploitation of Marine Resources in Temporal and Environmental Context

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

Putting Human Exploitation of Marine Resources in Temporal and Environmental Context By Paul L. Koch Diane Gifford-Gonzalez Widespread evidence exists for intensified resource use by humans in coastal California over the past several thousand years. This includes a shift from inland foraging in the early Holocene to use of marine shellfish, fish, mammals in the middle Holocene. Around 1000 B.P., human foraging changed again, shifting away from reliance on coastal resources to those of the interior. Around the same time, the northern fur seal, formerly common in central and northern California, disappeared from central California archaeological sites, never to reappear in aboriginal sites. These changes in settlement and subsistence have been interpreted by some as the result of resource depression caused by growing human populations. In contrast, researchers working in the Santa Barbara region, where there is a well developed record of Holocene variations in rainfall, ocean temperature, and upwelling intensity, contend that the late Holocene shift was climatically driven. This argument is part of a broader debate that links changes in human ecology in the southwestern U.S. to the Medieval Climatic Anomaly. This argument has recently been extended to explain human and marine mammal shifts in central California, but little paleoclimatic data at high-temporal resolution exist for this region, or for the region farther north, where northern fur seals were harvested into historic times. The timing of the earlier shift to intensified use of coastal resources in the middle Holocene (6000 B.P.) is intriguing as well. Elsewhere on the globe, evidence is mounting for a shift in ocean circulation and global climate at this time, perhaps relating to the onset of modern El Nino/La Nina climatic cycles. At present, well-constrained paleoenvironmental data from the central and northern California coast are lacking. Thus it is impossible to determine if changes in human settlement and resource use are the result of climatic forcing. In our multidisciplinary project, we will use direct 14C AMS dates of archaeological materials to construct a finely-textured temporal framework for the study of cultural, paleoecologic, and paleoclimatic changes on the central and northern California coast. We have several goals. Chemical and isotopic variations in mollusk shells will be a key source of information on past ocean conditions. Likewise, isotopic variations in marine mammals can reveal migration patterns and trophic dynamics, and how they changed with inferred changes in climate. As a consequence, we will focus our dating efforts on these materials. We anticipate the following results: 1) construction of a time series of mollusk shells from both central and northern California that will form the basis of future paleoclimatic research, 2) an assessment of whether or not stratigraphic relations at a number of California archaeological sites are reliable, or if they have been perturbed by animals burrowing and churning, and 3) precise information on the timing of changes in the marine mammal fauna and human communities in both regions. Detailed isotopic and faunal analyses will be conducted once we've established a robust chronologic framework.