That aspect of the work, led by Christoph P.E. Zollikofer and Marcia S. Ponce de Leon of the University of Zurich-Irchel in Switzerland, started with a CAT scan of the skull, which had become deformed during its 7 million-year-old interment. It looks as though it had been squeezed centrally from both ears, with the right side of the cranium shifting upward and the left pushed downward. "The thing was sort of squashed and unlike anything that had been seen before, so you could only say so much about it," Fleagle said.
With a detailed three-dimensional X-ray image in hand from the CAT scan, the team was able to move the pieces around -- on a computer monitor -- until they lined up and fit together in what appears to have been their original form. That image reveals a skull wider than initially anticipated, with round eye sockets that look more human than ape. The relatively vertical face and other cranial and dental features "support the conclusion that Sahelanthropus is a hominid," the team concluded.
In addition to fitting all the pieces together, the researchers did an experiment: They tried to get the virtual pieces to fit into the general outline of a hominid skull, and also tried to get them to fit into an outline of a 3-D ape skull.
In the first case, the pieces fit together almost perfectly. In the second, there were overlaps and gaps -- evidence that the reconstruction was correct.
"The digital restoration is excellent," said anthropologist Tim D. White of the University of California. "The original interpretation [that Toumai was a hominid] is probably correct."
