Development of a Stable Isotope Technique for Sourcing Olivella Shell Beads in California

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Shell beads comprised a type of currency for Native American Californians. In parts of the state, beads could be used to purchase goods, to buy one's way into elite social groups, or to acquire services such as labor from other individuals. Shell bead currency also facilitated prehistoric commerce. Native peoples established extensive trade networks to move obsidian, baskets, food, salt, and other goods. For unknown reasons, the shell of a certain small-bodied marine snail, Olivella biplicata - the purple olive, was chosen to serve in this capacity. Derived from the Pacific Coast, Olivella beads are found as far east as Utah, Colorado, and Idaho. A large number of these beads were made in Southern California in the Santa Barbara area where extensive bead production centers are well known. The prominence of these centers has led some archaeologists to propose that Santa Barbara "mints" were responsible for the production of most if not all beads, despite the fact that Olivella is found in abundance all along the California and Oregon coast.Jelmer Eerkens and Howard Spero will develop a method to fingerprint the source of shell beads using oxygen and carbon isotopes. Based on preliminary data from modern shells collected in Santa Barbara, Monterey Bay, Bodega Bay, and Southern Oregon, they have shown that shells growing in certain regions along the coast have distinctive isotopic signatures due to differences in seawater temperature and upwelling. With the current funding they will expand the geographic breadth of that study and include ancient shells to determine how far back in time their fingerprinting method can be extended. This basic research will ultimately allow archaeologists to address several interesting and related questions, some of which will be touched upon as part of the current research. Were, in fact, Santa Barbara inhabitants responsible for the production of all money beads found throughout the state? If so, did they maintain control over the production of such beads throughout all of prehistory, or did a "centralized mint" only appear at a certain point in time? If not, where else were shell beads produced? Finally, the research will also provide valuable paleoclimatic data on past changes in sea surface temperature and upwelling. Are conditions today similar to those in the past? If not, how have they changed through the millennia? Can we correlate other paleoenvironmental data (e.g., fishery production, vegetation, snowfall, etc) to ancient sea surface temperature and upwelling, so that we may better understand, and predict for the future, how changes in one affect the others?The investigators plan to incorporate the findings into an instructional module for school children at the Anthropology Museum at UC Davis, where over 500 K-12 school children visit each year. Children learn about pre-contact Native American lifeways and how archaeologists reconstruct the past from material remains. This module will show how technical-sounding analytical techniques (i.e., mass spectrometry) are used to answer simple-sounding questions (i.e., who traded with whom). Such outreach brings the past alive by providing interactive and hands-on experience with archaeologists and real artifacts.