Skulls bolster theory humanity arose in Africa

3 human fossils oldest ever found

June 12, 2003|By Peter Gorner, Tribune science reporter.

The fossilized skulls of two adults and a child who died 160,000 years ago in the badlands of northeast Ethiopia are the oldest examples of modern humans ever found, scientists reported Thursday.

The skulls, excavated from an archaic lakebed, are 60,000 years older than the earliest known specimens of ancient Homo sapiens.

Though the skulls appear to answer many questions, they are already provoking controversy in the most contentious of all sciences, paleoanthropology.

Egos clash like cymbals in the hunt for human origins. Many distinguished scientists spend their lives looking for fossils and never find anything. The few bones of human ancestors that do get unearthed are priceless beyond measure.

The new African skulls provide the first direct connection between Africa's famous ape-men and fully developed humans who started appearing around the world 100,000 years ago. They strengthen the "Out of Africa" hypothesis, which argues that humanity arose in Africa and not in multiple regions, scientists said.

"This pretty well wipes out Multiregion Theory," said Tim White of the University of California, Berkeley, co-leader of the research team. "But then, I doubt if the theory's proponents will give up willingly."

White said the fossils fit neatly into the time frame of the controversial "Eve Hypothesis," which suggests that genetic changes in mitochondrial DNA, which is passed unchanged from mothers to their children, could trace back the origin of everyone who has ever lived to a small population of Africans.

At its beginning, scientists have said, is an ancestral mother, an archetypical woman the scientists nicknamed Eve, who lived between 100,000 and 200,000 years ago.

Researchers studying the Y chromosome that fathers pass on to their sons have reached similar conclusions.

The new fossils also predate most Neanderthals and lack signs of their features. The African fossils provide strong evidence that Homo sapiens and the Neanderthals co-existed, rather than the former descending from the latter, the researchers said.

Neanderthals split off from the human family tree well over 300,000 years ago and died out about 30,000 years ago, perhaps driven to extinction by modern humans.

"These fossils show that near-humans had evolved in Africa long before the European Neanderthals disappeared," said F. Clark Howell, a co-leader of the research team.

"They thereby demonstrate conclusively that there was never a Neanderthal stage in human evolution," Howell said.

According to White, skull fragments bear cut marks made by stone tools and perhaps demonstrate a form of early mortuary practice.

The jaws and any bones below the neck were conspicuously lacking, he said, possibly indicating cannibalism.

"We have no way of knowing, but it clearly was intentional," White said.

Found in 1997

The new fossils, discovered in 1997 and undergoing analysis ever since, were described in this week's edition of the British scientific journal Nature.

The skulls were excavated near a village called Herto in the desolate Afar region of eastern Ethiopia, a rich fossil field about 140 miles northeast of Addis Ababa, the nation's capital.

The most complete of the new hominid fossils is an adult male cranium (skull lacking lower jaw) with heavily worn teeth, found embedded in ancient cemented sands.

It features a prominent forehead, flattened face and reduced brow that makes it recognizably human and clearly contrasts the projecting, heavily browed skulls of older hominid fossils.

White called the skull near-modern and definitely Homo sapiens, though it shared some traits with earlier ape-men. "The brow ridges are very strong, and the area of the neck muscle attachment is very robust. This was quite a big guy. A real man," White said.

The evidence of mortuary practice was identified on skullcap pieces representing a second individual.

The third individual, represented by a child's shattered cranium, was located nearby.

The Herto fossils form a transition between prehuman ancestors and later humans because they are the oldest fossils that have the facial features and brain cases of modern people, White said.

"We've lacked intermediate fossils between prehumans and modern humans, between 100,000 and 300,000 years ago, and that's precisely where the Herto fossils fit," White said.

He said the fossils also mesh with the molecular evidence that led to the Eve Hypothesis.

"That means we have two very different kinds of evidence leading to the same conclusion," White said. "In science, that's incredibly powerful."

From his days in the 1970s with former colleague Donald C. Johanson--when the two classified and won acceptance for the famous Lucy fossil as the oldest human ancestor--White has been a celebrated figure in the quest for human origins.

In previous studies, White and his Ethiopian colleagues discovered fossil remains dating between 5.2 million and 5.8 million years old that belong to the genus Ardipithecus, some of the earliest human ancestors known.