Hominid Origins

Abstract

The sequence of fossil-bearing sediments in the Manonga Valley, with an estimated age range of ~4.0–5.5 Ma, samples a critical period of time (from 4 Ma to 7 Ma) that is generally poorly represented in sub-Saharan Africa. Few other paleontological sites have sediments that fall into this time range, and many of these are difficult to date, or have relatively small faunas that have not yet been the subject of detailed study. The best paleontological information for this period comes from sites in the Baringo basin and Turkanabasin in Kenya, and from sites in the Middle Awash region of Ethiopia, where sizable faunas have been recovered from sediments that have been dated using radiometric techniques. The most important fossil collections are from the Mpesida Beds (6.4–7.0 Ma) and Lukeino Formation (5.6–6.2 Ma) in the Baringo basin, the upper Nawata Formation and Apak Member at Lothagam (~4.72–6.24 Ma) in the Turkana basin, and the Sagantole Formation (~3.5–4.5 Ma) and Adu-Asa Formation (~4.5–6.0 Ma) in the Middle Awash. It is important to note that these sites are limited geographi-cally to two relatively restricted areas within the East African Rift valley (i.e., in north-central Kenya and northeastern Ethiopia).