Understanding taphonomy and site formation processes for fossil human and primate sites is central to testing hypotheses about paleoenvironments and the natural selection of various traits and behaviors in our lineage. Strong inferences about paleoenvironmental and behavioral reconstructions, however, rest on demonstrated associations between both fossil and sedimentary environmental proxies and taphonomic actualistic data. On Rusinga Island, Kenya, Miocene and Pleistocene fossils have been collected and studied for a century, yielding a rich assemblage of early Miocene stem hominoids and catarrhines—Ekembo, Dendropithecus, Limnopithecus, Rangwapithecus, and Nyanzapithecus. Numerous mammalian, avian, reptilian, invertebrate, and plant fossils are preserved alongside these primates. Pleistocene fossils on Rusinga are often in association with Middle Stone Age tools made my early Modern Humans. Despite the long history of collection, little consensus has been reached about the paleoenvironmental contexts in Miocene Rusinga, in part due to faunal mixing and lack of broad taphonomic studies. Furthermore, behavioral reconstructions of have been limited by not engaging with taphonomic surface modification data. Pleistocene deposits are generally understudied compared to the Miocene fossils and behavioral reconstructions have been similarly limited. This dissertation examines taphonomic site formation processes of both time periods using archaeological style excavations, systematic surface collections and taphonomic data collection. Bonebed excavations and taphonomic data at Miocene R5-Kaswanga inform paleoenvironmental reconstructions and show that attritional predation and fluvial processes account for most of the bone accumulations. A survey of Miocene primate remains for trends in surface modifications suggest predation by creodonts, carnivores and avian raptors, indicating important selection pressures from predators. Bonebed excavations at Pleistocene Wakondo yield the first behavioral reconstruction of tactical hunting on Rusinga Island.