The Middle Stone Age on the Margins: Chronological and Archaeological Contexts for Hominin Behavioral Evolution in the Middle and Late Pleistocene of East Africa.

The later Middle through early Late Pleistocene (~100–400 ka) of East Africa is an important time and place for the evolution of our species. This period records the first appearance of Homo sapiens and spans significant technological changes including the decline of large handheld stone tools characteristic of the Acheulean, the development of stone tool technologies collectively known as the Middle Stone Age (MSA). These include diverse Levallois prepared core techniques and the manufacture and use of pointed weapons. It is in association with MSA technologies in sub-Saharan Africa that most of the behaviors characteristic of modern humans first appear. This doctoral dissertation provides new chronological and archaeological data relevant to hominin behavior associated with MSA technology in the Middle and Late Pleistocene of East Africa. Improved chronological resolution is achieved through tephrostratigraphy, the correlation of volcanic ashes, combined with chronometric dating in two regions: the Kapthurin Formation in the Rift Valley, Baringo, Kenya and the eastern Lake Victoria Basin of western Kenya. New data on hominin behavior is provided by archaeological excavations of two sites: 1) The 196-226 ka Sibilo School Road Site in the Kapthurin Formation. 2) The 33–49 ka site of Nyamita Main in the eastern Lake Victoria Basin. The archaeology of the Kapthurin Formation and the eastern Lake Victoria Basin are connected thematically by the presence of MSA technology. These basins are also connected stratigraphically and chronologically, as this study shows, by tephra correlations between them. Results of this work demonstrate: 1) Levallois prepared core techniques, important aspects of MSA technology, are shown to be \u3e380 ka in the Kapthurin Formation, ~100 kyr older than previously estimated in East Africa. 2) Long distance transport (\u3e166 km) of high quality obsidian for stone tool manufacture was a feature of hominin behavior associated with Middle Pleistocene MSA technology ~200 ka ago. 3) MSA technology persisted in East Africa later than 49 ka and perhaps later than 33 ka, after Later Stone Age technologies, often considered categorically superior, are documented in the region. By demonstrating both the early and late presence of various aspects of MSA technology and associated hominin behavior this work shows that tephrostratigraphy and the excavation of new archaeological material in East Africa are productive means of producing new and important data on the MSA and the evolution of human behavior