The 3.3-million-year-old female, of the species Australopithecus afarensis, is expected to provide important clues in understanding evolution. It also will likely reignite debate over whether a species thought to be among the earliest ancestors to humans was able to climb trees like an ape.

Researchers say it's unprecedented to have such a complete skeleton of a young child dating back so far. The discovery and initial analysis of the skeleton, found in the Dikika area of northern Ethiopia, were published in today's Nature journal.

Kimbel, science director of the Institute of Human Origins, said the find will help researchers sketch an evolutionary growth pattern for one of the earliest species of human ancestors."It's a very significant find," he said, adding that so much of the skeleton was recovered, "it's as though you could hold the skeleton in your arms like a 3-year-old baby. It's quite impressive in that respect."

The discoverer of the skeleton is Zeresenay Alemseged, a former postdoctoral researcher at ASU who now works at a German anthropology institute. The Institute of Human Origins, along with the National Geographic Society, provided financial and logistical support for the research.

The ASU institute's director, Donald Johanson, discovered the Lucy skeleton in 1974, a finding that revolutionized the understanding of human origins. She was believed to be a new species in man's evolutionary line. The discovery also challenged the belief that man didn't begin walking until later, when his brain grew larger.

Preparing the skeleton for analysis has been a delicate, five-year process. Alemseged, the lead researcher, chipped sandstone from bone fragments until key features could be seen. He is still years from fully exposing the skeleton.

"It's the same species as Lucy. As far as we can tell, the baby has no pelvis preserved, but Lucy does. On the other hand, Lucy has no shoulder blades, or scapula, and this skeleton has both."

A: "When you see the specimen, especially after the years of meticulous cleaning, it's really a shock to your system. Here's a 3-million-year-old skeleton of a 3-year-old infant. It's mind-blowing to see the entire skull. It's a strikingly visual experience, especially when you realize the chances of preservation for something like this are infinitesimally small. It's really thrilling."

A: "They were omnivorous and ate a wide variety of plant foods, probably augmented with insects. It was a pretty broad diet that focused on relatively tough vegetables, fruits or nuts. They were primarily bipeds (capable of walking), and this gets back to the debate over whether they had some degree of apelike locomotion. They had small brains, not much bigger than that of the same-size apes. If you were to see one in the distance, you would say, 'My goodness that chimpanzee is walking like a human.' "

A: "It's in a badlands deposit in northeastern Ethiopia. These are soft, sedimentary rocks deposited on the banks of the river millions of years ago. They've been slowly eroded. The fossils were buried due to periodic flooding and now, once again, water patiently exposes the fossilized remains, awaiting the discovery of patient anthropologists.. It's always hot there, even in the winter. It's like Phoenix in the summer."

A: "This is an area where there is a lot of disagreement. The scapula has a number of features reminiscent of gorilla anatomy. On the other hand, it has some human features as well. It's an intriguing mix. The question is how do you interpret apelike characteristics in the skeleton? Does it have a functional significance or is it evolutionary baggage that has no particular significance? This is a matter of scientific debate, and one we don't expect to resolve."

A: "The specimen is not even fully cleaned yet. When it was found, the bulk was encased in a block of sandstone probably the size of an American football. Only bits and pieces were poking out. . . . Each of the vertebrae consists of at least three pieces, and they are tiny, tiny fragments. You have to really be patient. We felt now was the time to put on record the preliminary findings and show it to the community."

The oldest and most complete child skeleton is a significant find because so many pieces were discovered. To date, researchers have found the skull, including jaws and teeth, and parts of the shoulders, ribs, spinal column, right arm, fingers, legs and left foot.

The skeleton will be important for understanding growth and development of an early human ancestor, said Fred Spoor, a London professor who worked with ASU Professor William Kimbel on analyzing the skull.

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