Bones in Africa Called Closest Yet to Missing Link

In a handful of teeth and skull fragments almost a million years older than anything else in the human family tree, scientists have discovered compelling evidence of a new species that may be humanity’s earliest direct ancestor.

It is the closest thing yet to the long-sought “missing link” between human beings and ancient apes, the scientists said.

The fossils, gleaned from a rugged river basin in Ethiopia, are the fragmentary remains of a child and 16 other small, apelike individuals of a previously unknown pre-human species that flourished in African woodlands 4.4 million years ago, an international team of researchers announced Wednesday.

“This species is the oldest known link in the evolutionary chain that connected us to the common ancestor (we share) with the living African apes,” said Tim D. White, a paleontologist at UC Berkeley’s Laboratory for Human Evolutionary Studies, who led the team that made the discovery near a village called Aramis.

The new species--named Australopithecus ramidus-- is a mosaic of primitive and advanced features, the scientists said. The creature’s jaw and teeth are similar to those of a chimpanzee, while other crucial details of anatomy suggest more human characteristics.

Several experts who have examined the fossils said the discovery offers the first direct glimpse into the era when humanity’s earliest ancestors veered off from other primitive primates, underscoring the relatively rapid pace of human evolution. The remains appear to date from a time shortly after the human family tree first branched, with one line leading to modern human beings and the other leading to the great apes of Africa.

The bones also buttress a theory long championed by molecular biologists who have argued that, based on genetic analysis, the first human-like species appeared as recently as 5 million years ago--about 25 million years earlier than conventional estimates. When first proposed in 1967, the idea was scorned by most anthropologists.

“When you combine these Aramis fossils with the evidence from the molecules, clearly Darwin was right--humans evolved from an African ape,” White said.

The tiny shards of bone--gnawed by ancient carnivores, buried in silt from seasonal floods--were recently unearthed by torrential desert rains. They include parts of the skull, the arm and the lower jaw of a child.

“This is the closest thing to the missing link we have ever found,” said Owen Lovejoy of Kent State University, a leading authority on human origins who has studied the find. “This thing is really primitive.”

All the remains are from the upper body and offer scant insight into how these earliest hominids, as the pre-human ancestors of humanity are called, lived or traveled. But other fossils found nearby suggest that their homeland was a flat, forested plain rich in wildlife such as rhinoceroses, bears, monkeys, bats and primitive antelopes.

The hominids are the first to be found in such a wooded environment, leading several scientists to speculate that the remains are evidence that the first stages of human evolution, such as the development of upright posture and walking on two legs, occurred among the trees and not in open grasslands as many scientists have argued.

The expedition’s discoveries were published in the science journal Nature, along with research by scientists from the Los Alamos National Laboratory and the Berkeley Geochronology Center that examines the botanical, animal and geological evidence accompanying the find.

The fossils were found in a region of East Africa that, during the past 30 years, has seen some of the most significant discoveries relating to primitive hominids. The Aramis area is north of Lake Turkana, where a 1.6-million-year-old hominid boy was found by Richard Leakey in 1984. It is 46 miles south of the Hadar, where paleontologists discovered the species represented by the famous Lucy skeleton. That species, called Australopithecus afarensis, was previously the oldest known human ancestor.

Donald C. Johanson, who discovered the Lucy skeleton in 1974, called the new find “terrific” and endorsed the idea of a new species of hominid that lived about 1.2 million years before Lucy.

“This is a very important piece of evidence that says that beyond 4 million years ago there appears to be a single line (of descent) and a single (human) lineage,” he said.

In 1979, White and Johanson described Lucy and related fossils as a new species most likely ancestral to all later hominids. Last year, a team led by White announced the discovery of more fossils from the same species that showed that hominids ranged over much of Africa for about 800,000 years.

A series of arresting discoveries announced this year has forced a reconsideration of much of what was assumed about human origins, from how quickly early hominids migrated out of Africa to what may have triggered the first use of tools.

But the story of the evolution of humankind as recorded in the sparse fossil record is composed largely of gaps and long silences. The creatures that predated Lucy’s kind remained a mystery until now.

The new species was found in a remote area west of the Awash River in Ethiopia. In the hardscrabble badlands there, expedition anthropologist Gen Suwa, from the University of Tokyo, spotted a single molar on Dec. 17, 1992, among the pebbles and hundreds of bone chips from other ancient animals whose remains had been ravaged by predators.

“I knew immediately it was a hominid,” he said.

In the year that followed, White and other expedition members turned up different bone fragments and teeth from 17 members of the species. The name of the new species-- ramidus-- is derived from the word that means “root” in the language of the Afar tribe, who live where the fossils were found.

“We think we are getting pretty close to a common ancestor between chimpanzee and human,” White said. “It is not a monkey. It is clearly a relative.”

Unearthing Human Origins

Scientists announced the discovery of prehuman fossils that are the closest thing yet to the missing link between the great apes of Africa and human beings. If confirmed by subsequent studies, the new species may prove to be near the root of the human family tree.

New species Australopithecus ramidus

Earliest known A. afarensis

Lucy

Homo neanderthalensis (Neanderthal)

Homo sapiens (Modern man)

WHAT: Teeth, skull fragments and arm bones from 17 members of a previously unknown pre-human species almost 4.4 million years old. Scientists said the new species--called Australopithecus ramidus --is believed to be humanity’s earliest known ancestor.

WHERE: At Aramis near the Awash River of Ethiopia. Site is about 45 miles from Hadar, where the famous Lucy skeleton was found almost 20 years ago. That species, called Australopithecus afarensis, was the previously oldest known human ancestor.

WHO: A team of scientists led by Tim D. White of the Laboratory for Human Evolutionary Studies at UC Berkeley, anthropologist Gen Suwa at the University of Tokyo and paleontologist Berhane Asfaw at the Ethiopian Ministry of Culture and Sports Affairs. The team is returning to the site next month.

Source: Nature, UC Berkeley.