One of the great gaps in the fossil record of the primate group containing Old World monkeys, apes and humans (catarrhines) has been the one spanning the interval from about 30 to 20 million years ago in Africa. This gap has now been filled by two sites of Late Oligocene age (approximately 24-27 million years old) in northwestern Kenya, both of which yielded new primate fossils during preliminary fieldwork in June, 2007. The current research is designed to find more primate fossils representing more complete skeletal remains from the new research areas, to put the primates into a solid framework of geological age and paleoenvironment, and to conduct phylogenetic and paleobiological analyses of them. Field camps will be established at the sites of Nakwai and Losodok, and research will be conducted with an interdisciplinary crew of anthropologists, paleontologists, geologists, including students, to recover primate fossils, other mammals, reptiles and birds, fossils of paleoenvironentally important plants, and rock samples for radiometric, paleomagnetic, and geo-isotopic studies. Together, analyses of these data will document patterns of primate evolution and paleoenvironment during the Late Oligocene of Kenya. This work will be integrated into existing knowledge of the important basal catarrhines of the early Oligocene and the great radiation of apes in the early Miocene, in order to better understand the evolutionary transition from primitive, early catarrhines to the earliest large-bodied apes of the superfamily Hominoidea.
Several issues of theoretical importance will be addressed. Some issues center around taxonomic assessments of Late Oligocene catarrhines: were true hominoids (members of the group containing only apes and humans) present at this time, or are the fossil ape-like primates precursors, or lateral relatives, of true hominoids? Had the evolutionary split between Old World monkeys and apes occurred by this time, as predicted by the latest molecular clocks? Other issues of theoretical importance center around the adaptations of these early ape-like primates, and the sequence in which they acquired ape-like traits, such as skeletal adaptations for their characteristic climbing movements, dental adaptations for frugivorous diets, and cranial adaptations associated with increasing brain size. The Late Oligocene is the period in which Africa, previously an island continent, was beginning to dock with the northern continents, and there is considerable theoretical interest in whether this geographic event was associated with African climatic change, shifts in environment or ecology, or changes in animal communities. Kenyan students and museum staff will be participate in this project, and many of the key analyses and laboratory procedures will be conducted with Kenyan colleagues, providing new opportunities and training for Kenyan paleontologists.
The discovery and interpretation of fossil primates has been a major focus of paleontological research in East Africa. A large number of different species were recovered in the 20th century, but little was understood about their context in time. Specifically, there was an apparent lack of fossils from the period between 20 to 30 million years ago - a crucial time during which it is believed that Old World monkeys and apes split from each other. Based on preliminary fieldwork conducted by our team and geological work by other researchers, there was a promising opportunity to fill this gap at two sites located in northwestern Kenya. In addition to recovering a larger number of fossil remains, out team sought to address specific questions about the phylogenetic and paleobiological significance of key animal taxa. This award funded three expeditions to these sites in the Nakwai and Losodok regions of Turkana, as well as additional fossil studies performed at the National Museums of Kenya, and geo-chronological analyses that were conducted in the U.S. In the process, professional paleontologists, geologists, paleobotanists, as well as graduate and undergraduate students were involved in recovering and analyzing late Oligocene fossil remains, ranging in age from approximately 24 to 27 million years old. As a result of the project, the number of fossil mammals known for the late Oligocene of Africa, both in number of remains and of taxa, has notably increased, including a rich non-primate fauna. The relevance of a fauna of late Oligocene age is not only its diversity, but also the fact that this was a period in which Africa, previously an island continent, was beginning to form a land connection with the northern continents, an event that has sparked considerable theoretical linterest in whether it was associated with African climatic change, shifts in environment or ecology, and/or changes in animal communities. Several of our discoveries have helped shed light on this issue, such as that of a new species of deinothere that helps explain the derivation of this group of proboscideans (elephant-like) from straight-tusked ancestors, as well as evidence for the very first true carnivores that have ever been found in the continent - a group that conquered Africa in later times, but whose specific arrival time had been hard to establish. A major discovery is that of a few dental specimens of what promised to be the oldest Old World monkey know to science. Furthermore, additional remains of the primate genus Kamoyapithecus were recovered, possibly including crucial skeletal remains, which would help in understanding their locomotion, and thus would give some insight into their habitat. One of the challenges of such a uniquely rare and rich fauna is the number of new taxa to be studied without an extensive amount of comparative material. Because of this, our collaboration with experts on various taxa has expanded since the beginning of this project and more specific descriptions of the new findings are being prepared for publication. One doctoal and one master's student have benefited from this award by utilizing recovered fossils for their dissertation/thesis analyses. Likewise, Kenyan students and museum staff, as well as an American undergraduate student and an Egyptian graduate student, have also particpated in the field activities and have gained considerable scholarly and field training. The large collections that have been recovered, stored at the National Museums of Kenya, provide a valuable source of information to future scholars. We anticipate that, as more extensive interdisciplinary comparisons are made and more fossils are recovered, we will learn more specific attributes of this very rare fauna, allowing us to accurately reconstruct the environment and mammalian fauna of such a crucial time in primate history.
