Earliest known ancestor of man found in Ethiopia

September 22, 1994|By Knight-Ridder News Service

SAN JOSE, Calif. -- The earliest known human ancestor -- a creature 4 to 5 feet tall that lived 4.4 million years ago -- has been found in Ethiopia, a team of Berkeley scientists said today.

The hominid, a new and much more primitive species of Australopithecus, pushes back the beginning of the human lineage by nearly a million years. It lived in a forest in what is now the Awash River region, surrounded by monkeys, antelopes, bats and other creatures.

It may have had the face of a chimpanzee, and researchers don't know yet if it walked upright or on all fours. All they have so far are a few dozen fossil fragments -- mostly teeth -- from 17 individuals. But from these scant clues, researchers have concluded that the creature must have been one of the first sprouts on the human family tree, appearing just after our line branched off from the one that led to modern apes.

It looks as though "if you went back a little bit further you'd have a chimpanzee or something very close to that," said Vincent Sarich, the anthropologist at the University of California, Berkeley, who first suggested 30 years ago that chimps are our closest relatives among the primates.

The discovery is "wildly significant," said Owen Lovejoy, an anthropologist at Kent State University who has examined the fossils. "The finds are fragmentary at the present time, but they're diamonds," he said.

As excavations continue and more complete skeletons surface, he said, they could help to answer some of the most intriguing questions about human evolution: When and why did we start to walk upright? Why did we leave the shelter of the trees for the open savanna? And why did we lose our sharp canine teeth in favor of kinder and gentler ones?

The scientists said they have enough evidence to declare the creature a new species: Australopithecus ramidus. The term "ramidus" comes from the Afar word for "root" and was chosen to acknowledge the contributions of villagers to the research. The first ramidus fossils were discovered in December 1992 by Gen Suwa, a researcher from the University of Tokyo. Walking over the barren, rocky ground in an arid region known for its hominid remains, he saw the glint of a molar among some pebbles.

"I knew immediately it was a hominid," Dr. Suwa said, "and because we had found other ancient animals that morning, I knew it was one of the oldest hominid teeth ever found."

Led by anthropologist Tim D. White of UC-Berkeley, the team spent two winters digging in the area, uncovering dozens of fossilized bones and teeth. Like those of other fossil animals found in the area, the hominid carcasses had been torn apart by scavenging animals, Dr. White said. "So we had pieces."

But the pieces were ancient indeed: Crystals of volcanic rock just below the hominid bones were dated by Paul Renne of the Berkeley Geochronology Center at 4.4 million years. An analysis of nearby animal fossils confirmed that date.

Previously, the oldest known human ancestor was Australopithecus afarensis, which lived up to 3.6 million years ago. Lucy is the most famous example; her partial skeleton, unearthed in 1974, showed that she walked erect. Scientists later found fossil footprints left in the mud by an afarensis adult and child; and in March, scientists said they had discovered the first complete afarensis skull.

The new set of fossils includes the jawbone of a child with one of its "baby teeth" still in place, the base of one skull and three bones from a single arm.

They are linked to humans literally by the skin of their teeth, Bernard Wood of the University of Liverpool said in a commentary in the journal Nature, where the discovery was reported today.

Modern people and hominids have a thick coat of protective enamel on their teeth; chimps have a thin one. The thickness of the enamel on the fossil teeth falls somewhere between.

The lone baby tooth is shaped more like one from a chimp than one from a human, Dr. White said. On the other hand, he said, the creature already had lost its ferocious-looking canines.

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