CHICAGO – A 3.3-million-year-old skeleton of a young child curled into a ball no bigger than a cantaloupe – a unique fossil described as “a bright beam of light” on human evolution – was unveiled Wednesday by paleontologists working in the sun-baked badlands of Ethiopia.

The tiny bundle of bones may be the best fossil yet found of the primitive human ancestor Australopithecus afarensis. That is the same species as the superstar fossil dubbed Lucy, an adult female discovered nearby in 1974.

The skeleton, described in the British scientific journal Nature and National Geographic magazine, represents the first juvenile remains of these ancient humanlike creatures, making the fossil the oldest child by far ever found.

“This is something you find once in a lifetime,” said Zeresenay Alemseged, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, an Ethiopian paleoanthropologist who led the team that discovered it.

The fossil offers clues about how the species blurred the line between ape and human. From the waist down, the skeleton looks like a human’s. But her upper body had many apelike features. Her brain was small, her nose flat like a chimpanzee’s and her face long and projecting. Her finger bones were curved and almost as long as a chimp’s.

“Clearly, we have a species in transition,” said Lucy’s discoverer, Donald Johanson, director of the Institute of Human Origins at Arizona State University. The species “sits at a critical point of human evolution.”

Some parts of the skeleton are missing – the pelvis, the lowest part of the back and parts of the limbs – but what is preserved is remarkably complete. The brain case, the lower jaw with most of its teeth, both collar bones, many vertebrae and ribs, the fingers, both kneecaps and the delicate bone that holds open the throat, called the hyoid, are all present.

“One must travel forward in time more than 3 million years, to a Neanderthal infant from Dederiyeh, Syria, to find a comparably complete infant skeleton,” anthropologist Bernard Wood of George Washington University wrote in an editorial for Nature.

“We don’t often get the opportunity to see a 3 to 4-million-year-old hominid in the course of growing up,” Wood said in an interview. “This fossil is a bright beam of life on the problem of human growth and development and how it evolved.”

The fossil hunting team happened upon the skeleton in 2000 in a region plagued by extreme heat, flash floods, malaria, wild beasts and occasional shootouts between rival ethnic groups.

Expedition member Tilahun Gebreselassie was the first to see the tiny face peering from a dusty slope. The skull was no bigger than a monkey’s, but a smooth brow and short canine teeth told Zeresenay right away that it was a small hominid.

Tucked beneath the perfectly preserved head, in a hard ball of sandstone, were many bones of the upper body.

The cause of death was not evident, though it may be that a flooding river rapidly buried the body in pebbles and sand, protecting it from the elements. Researchers estimate the child may have been 3 years old.

Etching away sandstone grains with a dentist’s drill, Zeresenay navigated between the tiny vertebrae and ribs so anatomical details could be seen. The task has taken him five years so far.

To him, what he has found suggests A. afarensis mainly moved around on two feet but also climbed trees when necessary, especially when young. The fossil’s shoulder blades resemble a young gorilla’s, suggesting the child could and did climb trees, but the angle of the femur from knee to hip is close to that of a modern human, implying she also walked efficiently on two legs.

Johanson said that in the years since he found Lucy he has come to agree that the species spent time in trees. “The females were only 3 1/2 feet and weighed about 60 to 65 pounds,” he said. “Trees offered protection. They might have been great places to sleep at night. Or to climb up and harvest fruit.”

Nearly a household word, Lucy remains one of the most important fossils ever unearthed. In the 1970s, she and her kind were the earliest prehumans yet discovered, symbolizing the ancestor common to all hominids, including human beings.

Johanson, who called Lucy “the mother of us all,” became a leading spokesman for a new science encompassing molecular biology, archeology, sociobiology, primate studies, geology and anthropology.

Today modern paleoanthropology brims with feuding iconoclasts who chew over each discovery, arguing what the bones tell us about our distant past.

Some scientists criticized the Ethiopian team for publishing findings before the specimen was totally extricated from the sandstone.

Russell Tuttle, a veteran anatomist and primate expert from the University of Chicago, called the specimen “valuable” but cautioned that any statements about it could be premature until it is fully cleaned.

“In brief, the field team deserves kudos for providing us with this interesting specimen and readers should have a salt shaker nearby as they read the articles at this point,” he said.

Wood said the specimen still takes his breath away.

“How can we find something that’s 3.5 million years old and is that complete? By the laws of nature, that shouldn’t be possible,” he said. “These tiny infants should have all been eaten, their soft bones rotted or blown away by the wind. This should not have happened. But it has.”

(c) 2006, Chicago Tribune.

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Distributed by McClatchy-Tribune Information Services.

AP-NY-09-20-06 1928EDT

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