Fossil deposits on the Kenyan islands of Rusinga and Mfwangano comprise one of the richest sources of information for understanding the origin and diversification of the earliest apes. Best known for the primitive ape Proconsul and catarrhine primates Dendropithecus, Nyanzapithecus, and Limnopithecus, Rusinga/Mfwangano sites also preserve copious mammal, reptile, bird, and invertebrate fossils, as well as rarely seen fossil elements such as leaves, seeds, fruits, and insects. Thus, it becomes possible to reconstruct not just the anatomy of these primates, but also their chronological context, aspects of their feeding ecology, habitat preferences, and the broader ecological community in which they thrived. This project will undertake new research on Rusinga/Mfangano to further our knowledge of the chronology and paleoecology of stem catarrhines and hominoids. Specific objectives are to: 1) establish stratigraphic and chronological control within and among primate fossil sites on Rusinga and Mfangano; and 2) reconstruct paleoenvironmental conditions throughout the geological sequence to assess the ecological parameters in which these primates lived. Work will be carried out over three summers and include basic stratigraphic analysis, absolute and relative dating, controlled fossil collection, analyses of stable isotopes, revisions of existing faunal collections, and dental microwear analysis. The intellectual merit of this project lies in combining geological, paleontological, and paleoecological methodologies to substantially advance our knowledge of hominoid evolution and adaptation through development of high-resolution chronostratigraphic data and detailed paleoecological models for Rusinga and Mfangano catarrhine primates. This project also has considerable broader impact in promoting education and cooperation at the local level, advancing local involvement in the preservation of the fossil heritage, employing local and national Kenyan workers, educating undergraduate and graduate students, and promoting international and interdisciplinary collaborations.
This project made several important contributions to our understanding of ape origins and evolution by completing new field research at the fossil localities of Rusinga and Mfangano Island, Kenya. The goals of this work were to answer the following questions: - What are the stratigraphic and temporal relationships among the sites on Rusinga and Mfangano, and between these localities and other fossil primate sites? - What type of paleoenvironment(s) supported the primates from Rusinga and Mfangano Islands? Answers to the first question were surprising and significant. Using stratigraphic analysis and new dating methods, we found that most of the fossil sites on Rusinga and Mfangano are substantially older than once thought, dating from 20.0 - 18.0 million years ago. This makes the earliest of these fossils contenporaneous with other sites in Kenya and Uganda, and calls into question previous models of ecological succession in the early Miocene of East Africa. We likewise discovered that the most fossiliferous localities on Rusinga, previously assumed to represent the same time period, actually span a much longer timeframe. Thus, earlier works that pooled together data from many sites will need to be revised, and new analyses must consider individual sites or stratigraphic units when trying to reconstruct paleobiology. Many new data sources were harnessed to answer the second question about paleoenvironments, including the discovery of more that eight thousand new fossil specimens. The organization and comparison of these will occupy us for many years to come, but some results can now be reported. The discovery at one site on Rusinga Island of a fossil forest system provided enough data to generate a high-resolution ecological reconstruction of this site. Based on the size and density of tree trunks, the types and organization of roots, the types of fossil leaves and vertebrate animals, and the characteristics of the soil, we can now say conclusively that the apes at this site lived in a dense, multi-storied tropical deciduous forest or rainforest. This discovery represents the first direct association between these primates and a specific habitat. Ongoing research at other sites on Rusinga and Mfangano will determine whether a forest like this was persistent across the time and space of these localities, providing the preferred habitat of these fossil apes, or whether more open woodlands or wooded grasslands may have also been important componments in their ecology. This research has important intellectual merit for the discipline of paleoanthropology, and for all sciences related to natural history. Rusinga and Mfangano comprise one of the most important localities in the world for understanding the the early diversification and subsequent evolution of the ape and human lineage. Even research on much younger species, including some of the early human ancestors, is based in part on our knowledge of these early apes. Hence, providing new chronological and ecolological contexts for Rusinga/Mfangano enhances our knowledge of ape evolution and has far-reaching impacts throughout paleoanthropology. Beyond this discipline, our results impact all research related to the evolutionary biology of the East African Cenozoic. Rusinga's rich fossil record of animals and plants makes it a key reference in the evolution of most African animal lineages. Our work, therefore, provides new and critical information for paleontologists, paleobotanists, geologists, and zoologists who are interested in Africa's prehistoric environment. This project has also generated substantial broader impacts. Not only has this work be presented to scientific audiences around the world, through conference presentations and publications, but it has also impact the public through museum exhibitions, news stories, public lectures, and workshops. Importantly, our research has significantly effected the local people of Rusinga and Mfangano through the training we provide and through our work with local students, teachers, administrators, government officials, and community leaders. This project has also provided access to research and knolwedge for a number of groups typically under-represented in science, including female undergraduate and graduate students and professionals, minority students, and Kenyan students and researchers.
