Development of grasslands and savannas in East Africa during the Neogene

The development of savanna-type grasslands is a relatively recent phenomena in East Africa. The stable carbon isotopic composition of paleosol carbonates from fossil localities in East Africa show that C 4 vegetation was present by about 8-9 Ma but made up only a relatively small proportion of the total biomass. Although the proportion of C 4 vegetation increased in the Pliocene and Pleistocene there is no evidence for the development of virtually pure C 4 grasslands, as is characterized by tropical grasslands today, until Middle Pleistocene times. This has important implications concerning the evolution of mammals in Africa, including hominids.