Isotopic reconstruction of social networks: geochemistry, ethnoarchaeology, and recent prehistory

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A milestone in the evolution of human cooperation was the formation of social networks linking individuals to others outside of the residential group. This project will investigate the development of social networks and their applications in pre-industrial societies by studying the movement of symbolic objects through gift exchange. Networks broadened spheres of interaction for the transmission of goods, norms, institutions, beliefs, and ideas, providing the building blocks for development of ever more complex culture. Understanding social and exchange networks in recent and ancient hunter-gatherers will shed light on how human populations were able to adapt to climatic fluctuations in the past and spread throughout the planet, using networks to buffer risk and become more resilient. The archaeological component will augment our knowledge of how ancient pastoral nomads adapted to hyper-aridity by tracking changes in network configuration in response to availability of natural resources and competition with neighbors. It will also provide a baseline for understanding the intended and unintended consequences of radically scaling up networks by electronic means today. By documenting recent changes in networks, the research will provide valuable insights for development efforts to assist groups in acquiring sustainable economic activities and alleviating poverty. Additional broader impacts derive from the chemical and geospatial data products developed in this project; landscape-scale models of environmental chemistry can be used to determine the source of illegally procured plant and animal products. The project will provide training and international collaborative opportunities for students and senior researchers.The project will apply analytical chemistry and geospatial modeling to determine the area of geographic origin, or provenience, of ostrich eggshell (OES) beads relative to their location of deposition or collection. In desert regions, ancient and recent hunter-gatherers and pastoralists used OES beads to make valued personal ornaments that were gifted to underwrite relations of mutual support that increased resilience to environmental, demographic, and social pressures. The distance between these origin and deposition points and the diversity in origin for beads in an object (e.g. a necklace) will be used as proxies for the scale of social networks. It is possible to determine the provenience of OES by measuring the ratio of two isotopes of the element strontium (Sr). The 87Sr/86Sr ratio is transmitted up the food chain from rock to soil and water to plants and ultimately into animals, creating a chemical signature linking an organism to the place where it acquired nutrition. This project has three major objectives: 1) construct geostatistical models of 87Sr/86Sr variation across the landscape in both study areas, 2) determine if well-documented exchange networks among recent foragers are detectible from 87Sr/86Sr analysis of OES beadwork collected by anthropologists in the 1950s-1970s, and 3) explore the potential of isotope analysis of OES for uncovering networks in desert regions over the last 4000 years when there was increasing aridity, plant and animal exploitation, and ritual activity.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.