HARVARD GAZETTE ARCHIVES

An Ancestor of Human Ancestors Found

By William J. Cromie

Gazette Staff

The bones of a distant relative of ours have been discovered in Uganda. He was a robust vegetarian, about the size of a chimpanzee, who swung ponderously through the trees as long ago as 20 million years.

The discovery pushes back by 5 million to 6 million years the time when modern apes separated from primitive apes. Humans evolved from the former about 5 million years ago; the latter went extinct around 8 million years ago.

"These are the oldest fossils found so far that belong to the evolutionary branch that includes living apes and human ancestors," says David Pilbeam, an anthropologist at the Peabody Museum of Archaeology and Ethnology. "We see in them key body features that identify all living apes, including chimps, who are our closest ancestors. The oldest humans were basically like chimps."

Pilbeam and his collaborators believe that the fossils represent a new genus and species that they have named Morotopithecus bishopi. "Moroto" comes from the place in Uganda where the creature's bones were found, "pithecus" means "apelike." "Bishopi" honors William Bishop, a British geologist who first found bones and teeth from this ape.

Redesigned Apes

Pilbeam, who is also Dean for Undergraduate Studies, first saw bits of Morotopithecus in the 1960s when Bishop brought pieces of its face, teeth, and spine to Cambridge University in England, where Pilbeam was studying. Pilbeam then worked on the material as part of a Ph.D. thesis at Yale University. He earned his Ph.D. in 1966 and visited the Moroto site in 1967-68.

"I was struck by the fact that, while the face and teeth of Morotopithecus were similar to those primitive apes, its lower spine resembled that of living apes," Pilbeam recalls.

During the 1970s and '80s, anthropologists collected a variety of fossils from apes that lived in East Africa between 15 million and 20 million years ago. They look completely different from living apes.

"Evolution basically redesigned apes," Pilbeam notes. "Just about every feature of living apes -- their torsos, internal organs, ligaments, and joints -- is different from their more primitive kin."

The fossils from Moroto seem to be an odd mixture of features from both modern and primitive apes.

In 1994 and 1995, anthropologists returned to that part of Uganda to gather more bones. The group included Laura MacLatchy, then a doctoral student of Pilbeam's, and Daniel Gebo of Northern Illinois University. They brought back two thigh bones and a part of a shoulder.

The heavy thighs would have allowed Morotopithecus to climb trees. The shoulder bone indicates that it could hang and swing from branches, probably in a quest for food and safety.

"While it moved on all fours on the ground, it was upright when in the trees," said MacLatchy who earned her Harvard Ph.D. in 1995. "Primitive apes, like monkeys, moved horizontally on the ground and on top of branches. In contrast, Morotopithecus could reach a greater variety of food while suspended from small branches."

"We had no idea that apes had evolved such modern features as long ago as 20 million years," Pilbeam noted.

Morotopithecus looks like nature put him together with pieces from extinct monkeylike apes and apes that now swing through trees in tropical Africa. This resemblance to living apes makes him their oldest known close relative. Morotopithecus didn't evolve directly into gibbons, orangutans, gorillas, and chimps, but he came from the same ancestors who did.

The bones found at Moroto came from at least two individuals. Taken together, however, not enough material exists for anthropologists to reconstruct details of what they looked like

Pilbeam and MacLatchy believe they had faces like apes and were 4 to 5 feet tall. Males weighed about 90 pounds and females about 45. They ate plants, predominantly fruits, and could move on the ground or by swinging from tree branches, albeit slowly.

"I've been interested in that ape for more than 30 years," said Pilbeam. "I think it raises all kinds of interesting questions about the ancestors of apes and humans."

Pilbeam, Gebo, and MacLatchy described their work with Morotopithecus in the current issue of Science, along with Robert Kityo of Kampla, Uganda; Alan Deino of Berkeley Geochronology Center in California; and John Kingston of Yale. MacLatchy is now at the State University of New York, Stony Brook. William Bishop died in 1977.