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.