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Special Report: Ancient Ancestors? Volume 54 Number 4, July/August 2001
by Angela M.H. Schuster

Kenyan fossils complicate the picture of early hominid evolution.

The discovery of a 3.5-million-year-old cranium near the Lomekwi River in northern Kenya is prompting a major reconsideration of the australopithecine branch of our family tree. Discovered by Kenyan Justus Erus and Meave Leakey of the National Museums of Kenya during 1998 and 1999 , the fossil, named Kenyanthropus platyops, is strikingly different from its contemporary and neighbor Australopithecus afarensis, the species to which the 3.2-million-year-old Lucy belongs.

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Leakey's find came on the heels of the discovery of what may be the earliest-known human ancestor, a diminutive 6-million-year-old creature represented by fossils from several localities in western Kenya's Tugen Hills. Their date, if accepted, pushes back the earliest-known ancestor by some 1.5 million years. According to excavators Brigitte Senut of the Musée National d'Histoire Naturelle in Paris and Martin Pickford of the Collège de France, the fossils represent five individuals of a species they have named Orrorin tugenensis.

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Paleoanthropologists Brigitte Senut and Martin Pickford say the split between australopithecines and human progenitors occurred prior to 6 million years ago, the date of Orrorin tugenensis. They argue that O. tugenensis and Praeanthropus (in which they place Australopithecus anamensis and some A. afarensis fossils) are ancestral to humans, while the australopithecine branch came to an evolutionary dead end 1.5 million years ago. Before now, scholars believed that the australopithecines were our earliest-known ancestors, our family lines diverging 3 million years ago. The position of Kenyanthropus platyops has yet to be determined.

Angela M.H. Schuster is senior editor of ARCHAEOLOGY.

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© 2001 by the Archaeological Institute of America
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