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Earliest Known Old World Monkey Skull

By Sean Henahan, Access Excellence

Carbondale, IL (7/24/97) A newly discovered 15 million year old monkey skull is shaking up previous notions of the evolutionary path of monkeys and humans.

Researchers found the skull on Maboko Island in Kenya's Lake Victoria. The skull belonged to a monkey belonging to an ancestral family called "Victoriapithecus". The skull dates to the Miocene period, between 7 million and 23 million years ago.

"This 15-million-year-old skull is significant because it flies in the face of what scientists have believed about how the earliest monkeys looked and behaved," said Brenda R. Benefit, an associate professor of anthropology at Southern Illinois University. "It also challenges commonly held beliefs about how the ancient ancestors of apes--and humans--looked.  And it influences where we can place other fossil catarrhines (Old World monkeys, apes and humans) on the evolutionary tree.  The concept of ancestor influences everything else down the line."

Cover image: Complete and undistorted skull of the Miocene ape Victoriapithecus 

The find is the only complete specimen skull from the Micocene period. The discovery is likely to contribute much to the understanding of the history and radiation of Old World monkeys. The skull possesses unexpected morphologic characteristics, preserving traits previously associated with extinct and living Sivapithecus and Pongo species. These traits may be primitive features of ancestral Old World higher primates in general.

Until the discovery of this skull, the oldest ever found, the consensus was that African and Asian apes had a common ancestor with a round head, short face and small teeth made for eating leaves, resembling a modern-day gibbon. But the Maboko Island skull has a low braincase, long face and big teeth.  It appears to have eaten fruit, not leaves.  While clearly a monkey, its forehead, cheeks and eye sockets make it look more like smaller version of an orangutan.

"It represents an animal that lies somewhere on the evolutionary tree between modern monkeys and the ancestor that gave rise to all monkeys, apes and humans," Benefit said.

The newly found skull also will change how scientists look at fossils of other animals.  For example, because it resembles the skull from a 32-million-year-old Egyptian primate, that animal also should fit on the family tree.

"The Egyptian skull didn't have the round head and short face of the gibbon-like model, so one group of scientists claimed it couldn't be an ancestor of monkeys and apes; another group said it was an evolved ape," Benefit said.

"Now we can see that the skull of this Egyptian primate is very similar to that of the earliest monkeys.  It fits right on the line that gave rise to both monkeys and apes."

Maboko Island is a treasure trove for anthropologists. Benefit and her team have uncovered 10,000 fossils there since 1982, about a third of which are primate fossils. The researchers found the skull in a trench first excavated by famed anthropologist Louis Leakey in 1949.

"We had left the trench intact for its historical value, but people were starting to farm in that area, so we decided it no longer made sense not to dig there," Benefit said. "After removing a layer of stone, we first found a complete crocodile skull, then a complete rhinoceros skull, then we found this one.  It was just lying there, looking up at us."

The skull  has become part of the permanent collection of the National Museums of Kenya in Nairobi.

The research appears in the July 24, 1997 issue of  Nature.

Related information on the Internet
AE: New Hominid Ancestor


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