Orrorin tugenensis : Millenium Ancestor
Martin Pickford (Professor, College de France, Visiting Professor to Kyoto University)

　Orrorin in the Tugen language means ﾒOriginal Manﾓ which is very appropriate because the fossils on which the genus is based are the oldest known remains of a bipedal hominid : a stunning 6 million years old. Stunning is a good adjective to apply to Orrorin because prior to 2000 most anthropologists thought that humans split from the chimpanzees only about 5 million years ago and that bipedalism arose in open country such as savannah. Orrorin completely changed that because it shows that fully bipedal hominids already existed 6 million years ago, and that they lived in wooded to forested areas. Thus, scientists are having to revise their ideas about the timing of events in hominid evolution, and the environmental conditions in which bipedalism arose. Basically, the discovery showed that many of the scenarios about human origins were wrong and that some avenues of research such as molecular biology are going to have to review their approaches to the study of the relationships between humans and apes.

　Orrorin was about 1.5 metres tall, weighed about 35 kg, walked upright on two feet when on the ground but could climb trees, and its teeth show that it was an omnivore. Bite marks on some of the bones indicate that Orrorin fell prey to carnivores on a regular basis. Originally based on 13 fossils, continued excavations at the site have yielded additional material, and we now have 22 specimens of Orrorin available from four localities within the Lukeino Formation. These reveal that most of the teeth and much of the skeleton of Orrorin are not like those of chimpanzees, but are much more like those of humans. We now think that hominids diverged from apes about 7-8 million years ago, or even earlier. Only new discoveries will enable us to determine more accurately when the ape-human split occurred. It now seems sure that hominid origins occurred in Africa during the Miocene period.