Collaborative Research: Rodent Diets and Habitat Reconstructions in South Africa: an Actualistic and Applied Multidisciplinary Study

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With National Science Foundation support, Drs. Sponheimer, Ungar, and Passey and an international team of colleagues will investigate the environmental context of human evolution. The team includes researchers from the U.S., Canada, Israel,and South Africa who will use their expertise in vertebrate paleontology, isotopic geochemistry, wildlife ecology, and human paleobiology to study human paleoecology through the lens of rodent dietary ecology. It has long been recognized that the ecological diversity and small home ranges of rodents make them particularly useful tools for reconstructing past environments. However, studies of rodent faunas have traditionally made assumptions about the ecology of fossil specimens rather than measuring dietary attributes directly. In contrast, this project will directly determine rodent diets to investigate the relationship between modern rodent dietary ecology and habitats, and then apply this knowledge to the South African human fossil record. Diet will be studied using dental microwear texture analysis, stable carbon isotope analysis, and strontium isotope analysis. The first two provide direct measures of dietary attributes (e.g., mechanical properties of foodstuffs, tree fruits/leaves versus grasses), while the last allows determination of where animals lived on the landscape, potentially resulting in more spatially-refined environmental reconstructions. The project will have three phases. In the first phase, the research team will conduct an extensive study of the relationship between modern rodent diets and habitat features. In the second phase, the team will determine the degree to which the diets of modern rodents from owl roosts reflect local habitats, essentially investigating the degree to which owl predation biases the environmental signal. The last phase will entail application of this knowledge to fossil sites in and around the Sterkfontein Valley, South Africa that are from ~2.5 million to ~700 thousand years old. The intellectual merit of this project is that it will provide new evidence of early hominin ecology and environments, and in so doing, will help address questions about hominin adaptations and evolution. For instance, did humans putative ancestors, big-brained early Homo, emerge in Africa only after significant deterioration of preferred enviroments, and did such environmental change contribute to the extinction of our smaller-brained, and presumably less adaptable, evolutionary "cousin" Paranthropus? It will also establish a firmer basis for using rodent dietary ecology to reconstruct paleoenvironments, which will be of broad utility at other archaeological and paleontological sites. In addition, it will mark the first time that multiple techniques have been used to investigate the intersection of animal diets, abundances, and environmental/climatic parameters over long (2 million year) timescales. Furthermore, the analytical developments to be made as part of this project will be of use for fields beyond archaeology including biological anthropology, geology, geochemistry, conservation ecology and paleontology. The broader impacts of this study are that it will foster international collaboration, provide training for students from underrepresented groups, enrich undergraduate teaching and graduate mentoring, and be used as a platform for bettering public understanding of science and technology. This is especially relevant for the University of Arkansas, a public university in an underfunded EPSCoR State.