A nearly 7-million-year-old skull recently described as the earliest known member of the human evolutionary family instead represents an ancient ape, say anthropologist Milford H. Wolpoff of the University of Michigan in Ann Arbor and his colleagues. The creature, Sahelanthropus tchadensis (SN: 7/13/02, p. 19: Evolution’s Surprise: Fossil find uproots our early ancestors), has more in common with fossil and modern apes than with fossil ancestors of humans, the researchers argue in the Oct. 10 Nature.
The specimen’s teeth resemble those of females in several fossil-ape lineages, they contend. As in gorillas today, the heavy brow ridge of Sahelanthropus worked with other skull elements to anchor powerful chewing muscles. Also, the position of the spinal cord opening in the skull’s base indicates that this individual didn’t regularly hold its head upright or walk on two legs, in the scientists’ view.
Two of Wolpoff’s coauthors regard their own 6-million-year-old fossil discovery as the earliest human ancestor (SN: 7/14/01, p. 20: Earliest Ancestor Emerges in Africa).
The issue is hardly settled. In a response in the same issue of Nature, Sahelanthropus discoverer Michel Brunet of the University of Poitiers in France says that, Wolpoff’s group improperly aligned many of the skull’s features and overlooked dental similarities to later fossil ancestors of humans.
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