Scientists digging in Ethiopia's desert have found the most complete skeleton yet of a prehistoric ape-man species thought to be a forerunner of humans.

The skeleton belongs to a three-year-old female from the primitive pre-human species called Australopithecus afarensis. She died of unknown causes more than three million years ago.

The first specimen of this group is the fossil nicknamed Lucy, a 3.2 million-year-old adult female discovered in 1974. The child's skeleton, discovered nearby in 2000, is about 150,000 years older than Lucy and far more complete, with fingers, a foot, and a torso in addition to a skull.

One of the discoverers, Zeresenay Alemseged of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, says no previous fossil of a baby pre-human has consisted of more than a partial skull, jawbone, or some teeth. Because this one is in such good condition, Alemseged says it could reveal what this human ancestor really looked like.

The skeleton offers new clues about how the afarensis species blurs the line between ape and human. The angle of the thigh bone from knee to hip is very human, implying she walked on two legs. But her torso is ape-like, as noted by another co-author of the research, Fred Spoor of University College London.

Spoor says this group of pre-humans was basically walking chimps. Zeresenay Alemseged points out that brain size of his specimen is that of a chimp, her neck is short and thick, her fingers are curved, and her shoulder blades, or scalpulae, are like a gorilla's.

The journal Nature published the research Thursday.