RESEARCH ON EAST AFRICAN CATARRHINE AND HOMINOID EVOLUTION (REACHE): A REGIONAL APPROACH TO UNDERSTANDING EARLY MIOCENE PALEOBIOLOGY AND PALEOENVIRONMENTS

Early Miocene deposits in East Africa provide the best opportunity for studying the origin and diversification of the hominoid clade. However, developing this detailed understanding of early hominoids and other catarrhine primates cannot be done through the study of any single fossil site. Instead, a regional perspective is needed. For this reason, we established a research consortium (REACHE) to develop regional geochronology, paleoecology, paleoenvironment, and biogeography of early Miocene fossil sites across East Africa. Here we report results from REACHE project sites for which we now have new paleontological and geological data. Preliminary analyses indicates that most of the REACHE sites experienced repeated environmental disturbances, driven by a variety of mechanisms, which may have influenced local habitats, faunal community composition, and the functional-adaptive morphology of early hominoids. New fossil collections from Karungu document a greater than expected diversity of catarrhine primates. Geological analyses indicate that the fauna lived in along a fluctuating lake margin in a dry, seasonal paleoclimate possibly prior to the eruptive phase of the nearby Kisingiri Volcano. Work at Tinderet has resulted in the collection of many primate fossils, including a partial cranium of Rangwapithecus gordoni. Geological fieldwork indicates that landscapes at all of the Tinderet sites were dynamic, with intervals of landscape stability punctuated by physical disturbance and landscape reorganization following volcanic fallout, lahars, and fluvial deposition. Fieldwork at Napak, Moroto, and Bukwa has also resulted in the discovery of new primate specimens. Analyses of paleosols and stable isotopes of bulk organic matter and herbivore enamel indicate variability in paleovegetation and paleoclimate within and between the sites. Fieldwork at West Turkana has documented dense accumulations of fossils, including many new specimens of the catarrhine primates Turkanapithecus and Simiolus. Future research will be focused on refining interpretations and providing better age constraints so that we can more fully assess the relationship between paleoclimate, paleoenvironment and catarrhine and hominoid evolution.