HOTTER, DRIER, AND MORE OPEN? GEOCHEMICAL PERSPECTIVES ON 10 MYR OF ENVIRONMENTAL CHANGE AND HUMAN EVOLUTION IN AFRICA

Linking human evolution to environmental change is nearly as old as the concept of evolution. As soon as fossils of early humans were identified, questions were posed about how they fit into a story of changing vegetation and climate. Did human evolution occur amidst a backdrop of (or in part because of) expanding grasses and the development of hot, arid environments? Answering these questions rigorously requires many different types of data on a range of spatial and temporal scales. The collective communities of paleoanthropologists, paleontologists, archaeologists, geologists, ecologists, and climate scientists have made huge strides in addressing these questions in the past 25 years. Among the many data types used, the stable isotope composition of soil carbonates and mammal teeth has been a key resource for exploring the links between human evolution and environmental change. Soil carbonates and teeth have been so useful in part because the materials are abundant at most hominin sites and because the isotopic data from them can be readily aggregated to address landscape, ecosystem and continental scale questions. In this talk we will review how carbon and oxygen isotopes of soil carbonates and teeth have informed our understanding of the history of C₄ grasslands, woody cover, ecosystem structure, temperature, aridity and hominin diet in Africa over the past 10 myr. We will explicitly address how these records have informed, and in some cases challenged, perspectives of human evolution. The latter portions of the talk will focus on how new directions in isotope geochemistry, specifically triple oxygen isotope and clumped isotope geochemistry, and how we can use these new types of data to refine our understanding of environmental change in Africa and answer long-standing questions about the dynamics of temperature, aridity and vegetation. These techniques serve as some of the latest examples of how innovation in different disciplines continues to be an essential part of placing human evolution into a firm ecological, climatic and tectonic context.