DURHAM, N.C. -- A surprisingly complete fossil skull of an ancient relative of humans, apes and monkeys bears striking evidence that our remote ancestor was less mentally advanced than expected by about 29 million years ago.
The second and most intact cranium found of Aegyptopithecus zeuxis was identified by Duke University primatologist Elwyn Simons, who is announcing the find this week with several colleagues. Because of the new specimen's remarkable wholeness, Simons and his colleagues were able to subject it to micro CT scanning, a computerized X-ray technique that can be used to calculate the approximate dimensions of the brain the cranium once encased.
Based on previous fossils collected at the same dig site in a quarry outside Cairo, scientists had hypothesized that this early monkey already would have had a relatively large brain, said Simons, a professor of biological anthropology and anatomy.
But the researchers' new report, which displays the computer-reconstructed brain as a false-color red mass within the grey skull case, suggests that the species "had a brain that might have been even smaller than that of a modern lemur's," Simons said. "This means the big-brained monkeys and apes developed their large brains at a later point in time." Simons named this creature Aegyptopithecus zeuxis -- or "linking Egyptian ape" -- after his team found the first skull in 1966.
Simons and his colleagues reported the findings online during the week of May 14 in the journal Proceedings of the National Academy of Sciences. The work was supported by the National Science Foundation and the Leakey Foundation.
Sufficiently tiny to rest in Simons' palm, the new 29-million-year-old skull is less than half the size of the 1966 skull. Simons said he and his collaborators first thought it might represent a new species.