["International Journal of Osteoarchaeology, EarlyView. ", "\nABSTRACT\nThe study of the Eastern African archaeological record is essential for understanding the origin and evolution of the Middle Stone Age (MSA). However, Olduvai Gorge, one of the primary regions in human evolution studies, has few sites associated with the MSA. The zooarchaeological and taphonomic study of two MSA sites, Victoria Cabrera Site (VCS) and Dorothy Garrod Site (DGS), allows us to understand the dynamics of accumulation of faunal assemblages in the gorge. While VCS is the result of accumulation by water flows, DGS is the result of human activity, identified especially by bones burned by intentional fire action and by intentional fracturing for bone marrow extraction. The paleontological study has allowed us to compare the taxonomic abundance of the sites with current data from various ecosystems, along with analyses of stable carbon (δ13C) and oxygen (δ18O) isotopes and dental microwear analysis of tooth remains. We have verified that the dominant environment of Olduvai Gorge at this time was characterized by open C4 savanna.\n"]