One of the major lacunae in our knowledge of African hominoid evolution concerns the origins of the chimpanzee and gorilla. Several thousand specimens from the Plio–Pleistocene of Africa have been attributed to Hominidae (sensu stricto) of which only a few, including Ardipithecus ramidus, have been re-interpreted by some authors as possibly representing an ape rather than a hominid (Senut, 1998). Four recently discovered ape-like specimens from the late Middle Miocene (12.5 Ma) and Late Miocene (5.9 Ma) of Kenya partly fill the gap in the fossil record of African apes, and show some morphological and metric affinities with teeth of chimpanzees and gorillas. If these few specimens from Kenya are indeed more closely related to chimps and gorillas than to hominids, then this implies that the dichotomy between African apes and hominids occurred several million years earlier than is currently estimated by most researchers. Furthermore these ape teeth from Ngorora and Lukeino suggest that extant African apes evolved in Africa, and did not immigrate into the continent from Europe or Asia.
2005 The Anthropological Society of Nippon