Image: Juvenile A. afarensis
Zeresenay Alemseged  /  ARCCH
The fossilized skull of a 3-year-old female from the species Australopithecus afarensis exhibits some characteristics of apes as well as humans.
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updated 9/20/2006 6:33:29 PM ET 2006-09-20T22:33:29

Move over, Lucy. Welcome, little Selam.

And let the debate about you and your brethren go on.

Lucy is probably the most famous fossil find in human evolutionary history — the partial skeleton of what was once a 3 1/2-foot-tall adult of an ape-man species, and named for a Beatles song that played over and over in camp the night of its 1974 discovery in Ethiopia.

Now Lucy has a young companion: Selam, the remains of a 3-year-old female of the same species, called Australopithecus afarensis. Selam lived some 3.3 million years ago, more than 100,000 years before Lucy.

"It's a pretty unbelievable discovery, to be honest," said Will Harcourt-Smith of the American Museum of Natural History in New York. "I think it's sensational."

He and others say the skeleton provides a trove of information, some of which will fuel a long-standing debate that "makes the Middle East look like a picnic," said human-origins expert Bernard Wood of George Washington University.

At issue: whether afarensis, which walked on two legs on the ground, could also climb trees easily and move around in them with agility. Selam hasn't settled the debate, but it does provide new evidence of climbing ability.

Selam's discovery in northeastern Ethiopia is reported in Thursday's issue of the journal Nature by Zeresenay Alemseged of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany; Fred Spoor, professor of evolutionary anatomy at University College London, and others.

Selam was discovered in 2000. Scientists have spent five painstaking years removing the bones from sandstone, and the job will take years more to complete. Judging by how well it was preserved, it may have come from a body that was quickly buried by sediment in a flood, the researchers said.

"It's a once-in-a-lifetime find," said Spoor.

Scientists already knew afarensis had long arms that dangled just above the knees, just the kind of feature that could indicate climbing ability. The debate centers on whether such traits are true signs of climbing ability in afarensis or just evolutionary baggage.

Spoor said so far, analysis of Selam does seem to indicate some climbing ability.

While the lower body is very human-like, he said, the upper body is ape-like:

  • The shoulder blades resemble those of a gorilla rather than a modern human.
  • The neck seems short and thick like a great ape's, rather than the more slender version humans have to keep the head stable while running.
  • The organ of balance in the inner ear is more ape-like than human.
  • The fingers are very curved, which could indicate climbing ability, "but I'm cautious about that," Spoor said. Curved fingers have been noted for afarensis before, but their significance is in dispute.

A big question is what the foot bones will show when their sandstone casing is removed, he said. Will there be a grasping big toe like the opposable thumb of a human hand? Such a chimp-like feature would argue for climbing ability, he said.

Yet, to resolve the debate, scientists may have to find a way to inspect vanishingly small details of such old bones, to get clues to how those bones were used in life, he said.

Selam also revealed just the second hyoid bone to be recovered from any human ancestor. This tiny bone, which attaches to the tongue muscles, is very chimp-like in the new specimen, Spoor said.

While that doesn't directly reveal anything about language, it does suggest that whatever sounds afarensis made "would appeal more to a chimpanzee mother than a human mother," Spoor said.

Selam includes the complete skull, including an impression of the brain and the lower jaw, all the vertebrae from the neck to just below the torso, all the ribs, both shoulder blades and both collarbones, the right elbow and part of a hand, both knees and much of both shin and thigh bones. One foot is almost complete, providing the first time scientists have found an afarensis foot with the bones still positioned as they were in life, Spoor said.

The work was funded by the National Geographic Society, the Institute of Human Origins at Arizona State University, the Leakey Foundation and the Planck institute.

© 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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