Doctoral Dissertation Research: Comparative paleoecology of three contemporaneous Early Miocene catarrhine sites in East Africa

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When does absence of a species at a fossil site truly mean that the species was absent from a once living community? This question will be addressed by a comparative study of the East African primate fossil record. The East African fossil record between 21 and 17 million years ago (Early Miocene) contains abundant remains of early catarrhines (the mammalian group that includes monkeys, apes, and humans). The fossil sites of Songhor, Koru, and Napak in East Africa contain different combinations of catarrhine species, despite being very close in space and time (19-20 million). Some species are found at all sites, while others are found at only one. The goal of this dissertation research is to explain these differences and to understand their ecological significance. It has previously been proposed that these different catarrhine distributions are the result of habitat differences between these areas during the Miocene. If this were true, we would expect to find similar differences recorded in the rest of the mammalian fauna. The hypothesis that catarrhine differences are due to habitat differences will be tested through a comparative study of both the catarrhine and non-catarrhine mammalian fossils from these three sites. In addition, alternative reasons why these catarrhine assemblages might vary will also be tested. These include: (1) sampling bias, (2) preservational or taphonomic biases, and (3) fossil collecting biases. Each of these factors can substantially alter the composition of fossil assemblages, even if the living communities from which the fossils derived were identical. Therefore, testing for these factors is critical in any paleontological study that seeks to understand interlocality variation. Finally, data on the distributions of modern African catarrhine communities will be used to create models of what catarrhine distributions should look like in the Miocene fossil record. This research is important and interesting because the catarrhine fossils under study represent the earliest members of the monkey-ape-human lineage, including the earliest known monkey, and the earliest well-characterized ape. Further study of these fossils and their associated faunas will increase our understanding of the ecological differences among Early Miocene primates. This will have important implications for understanding later stages of catarrhine evolution, including that of our own species. In particular, this study will highlight the important effects that sampling biases have on the fossil record, a topic that is only rarely addressed in paleoanthropological research. Also, this research will have significance more widely in the biological sciences because it will incorporate methods from the fields of both paleontology and ecology. The broader impact of this project is that it will encourage international collaboration with researchers at the National Museums of Kenya and the Uganda Museums. Inclusion of traditionally underrepresented groups is addressed by promoting the active involvement of African researchers in this project. All fossil data collected will be integrated into the National Museums of Kenya database currently being designed so that the data can be disseminated widely to other researchers. In addition, results will be published in peer-reviewed journals and presented at scientific conferences.