A central issue in archaeology is understanding how people were influenced by past environmental change and how they, in turn, actively shaped ecosystems and organisms around them. To explore those questions, some archaeologists have attempted to understand the origins of hierarchical sociopolitical systems among the densely populated coastal regions. Drawing on the analysis of artifacts, village structure, human subsistence, and high-precision climate records, archaeologists have rigorously debated the impact of hypothesized declines in marine productivity and extended El Niño conditions vs. extended drought. Even in contexts with exceptionally high-resolution marine climate records in the world, interpreting past climatic data can be incredibly challenging where surface oceanography across the region is highly variable. This project provides training opportunities for several undergraduate and graduate students, especially members of historically under-represented groups and Indigenous communities, and will support a wide variety of outreach activities.<br/><br/>This research seeks to understand when and why cultural complexity arose along one such region and any links it may have to past changes in climate. To address these issues, the researchers draw on the analysis of novel molecular/isotopes (compound-specific isotopes of amino acids or CSI-AA) in shells obtained from archaeological sites. CSI-AA is well preserved in archaeological shell and can directly record climate-linked shifts in local oceanography, including nutrient sources, baseline primary production, trophic structure, and algal community composition. This analysis offers a new, highly localized source of past climate variation and environmental productivity to help address the central research questions. This project is the first systematic archeological application of CSI-AA analyses addressing broad social, political, and cultural developments in California and will have far reaching implications for archaeological research on past environmental change around the world.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.