World's oldest ape fossil discovered

The fragile remains of the small creature, first discovered in 1992 in Ethiopia's Afar region and determined to be a new species in 1994, is the earliest known skeleton from the human branch of the primate family tree, scientists say.

Research into the Ardipithecus ramidus, nicknamed "Ardi," provides new insight into how hominids - the family of "great apes" that includes humans, chimpanzees, gorillas and orangutans - may share a common ancestor.

A team of scientists from 10 countries participated in Ardi's discovery, and 11 reports on research into the find are published in the special issue of Science.

"So this new evidence, coming as close as we've ever come to that last common ancestor really allows us to infer what that creature was like," said Tom White of the University of California at Berkeley, who collaborated on the study.

Los Alamos National Laboratory geologist Giday WoldeGabriel, who led the field geology investigations and sampling of ancient lava and ash used to determine the age of the fossilised remains, hailed the "fascinating and important discovery" of "mankind's oldest
relatives."

The scientists estimate that when she was alive, Ardi weighed about 50 kilograms and was 1.2 metres (four feet) high.

Before Ardi's discovery, the earliest well-known stage of human evolution was Australopithecus, a small-brained, bipedal "ape man" species that lived between four million and one million years ago.

The most famous remains belonged to "Lucy," a 3.2-million-year-old set of fossils found in 1974 some 72km north of where Ardi was discovered.

After Lucy's discovery, researchers expected earlier hominid remains to show a chimpanzee-like anatomy demonstrating genetic similarity between humans and chimps.

But the Ardipithecus ramidus fossils do not support that hypothesis, said White, a professor at Berkeley's Human Evolution Research Centre and Department of Integrative Biology.

"In fact, this creature is a very interesting mosaic... neither chimpanzee nor human," he said, noting that the fossil's hand is "even more primitive" than a chimp.

While the chimpanzees have very broad front teeth because they are fruit eaters, the Ardipithecus is "much more of an omnivorous creature," noted White.

"It turns out that frugivory (fruit eating) evolved along chimpanzee lineages," he said.

Fresh-water springs and small patches of dense forest made up Ardi's woodland home, according to the researchers. Palm trees grew along the forest edges and grasslands extended into the distance.

Researchers also found fig and hackenberry tree remains at Ardi's site, as well as snails, owls and parrots, small mammals including mice and bats, and a variety of other animals including porcupines, hyenas, elephants, giraffes and several types of antelope.

Ardi had a chimp-sized brain even though its face was smaller than a chimpanzee's. It had smaller incisors, and small canines, especially among males, according to White.