Study on origins of man and living apes in East Africa

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As shown in the title of our project, the major objectives have been to make clear the origin of hominids and origin of modern African apes. Originally, we had planned to conduct field surveys in Kenya and Zaire. The former was to discover fossils of proto-hominids, and the latter was to discover ancestors of chimpanzees and gorillas. A political situation of Zaire, however, has been worse since late spring of 1991. Therefore, we stopped having the field survey in Zaire. The areas studied in Kenya are Samburu Hills and Nachola area.On the basis of stratigraphy, the Neogene System in the areas is divided into following seven formations in ascending order : Nachola F. (19-15Ma), Aka Aiteputh F. (15-10Ma), Namurungule F. (10-7Ma), Nanyangaten-Kongia F. (7-5Ma), and Tirr-Tirr F. (4Ma). From the geological and geochronological data, an extremely marked structural gap is recognized between the Namurungule and Nanyangaten formations indicating many faults in Nachola, Aka Aiteputh and Namurungule formations but few in the upper formations from Nanyangaten Formation. The faults in the lower three formations is indicating a major tectonic movement of rift system in age from 9 to 8 Ma.The numerous equid and bovid remains have been found from the Namurungule Formation. These taxa indicates the open woodland to savanna environments. It seems that the Namurungule Fauna might have been the forerunner of the modern Sub-Saharan fauna in savanna and woodland environments. A large hominoid, Samburu-hominoid, was discovered from the formation. The hominoid might have been terrestrial knuckle-walkers or bipeds. Additional discoveries of the hominoids are strongly expected for a discussion of the origin of hominids.