SCOTT SIMON, host:
In human evolution, the development of the foot was a big deal. With its high arch and stiffness, the foot led to long-distance walking, running, even podiatry. It's in dispute is just when this anatomical wonder evolved. Now scientists have discovered a bone they think may answer that question. Other experts say, not so fast.
NPR's Christopher Joyce has this story on some new fossil footwork.
CHRISTOPHER JOYCE: If the human foot were a building, it would be a cathedral. Twenty-six bones, and more than a hundred muscles and tendons form an arched limb that's stiff but elastic too. It's the kind of foot you need to quit living in the trees and make a home on the range.
William Jungers at Stony Brook University in New York says the foot led our ancestors down the evolutionary path.
Dr. WILLIAM JUNGERS (Anatomical Sciences, Stony Brook University): It's sort of a window into humanity.
JOYCE: The modern foot probably came before the modern brain. But when and how? Now scientists have a bone from Ethiopia that they claim has a radical message - that the first full-time walkers with the first modern foot were not human at all. They were Australopithecus. That would be Lucy, the sort of half-ape, half-human who lived a couple of million years before humans evolved.
The bone is the fourth metatarsal, the long bone that connects your heel with your fourth toe. It's a little over three million years old. Anthropologist Carol Ward from the University of Missouri is one of the scientists who studied it.
Dr. CAROL WARD (Anthropology, University of Missouri): What this fossil does is shows us that the foot of Australopithecus was fully human like. The bones of the foot were arched from front to back and from side to side and the foot was very stiff and inflexible up through the middle.
JOYCE: Writing in the journal Science, Ward says the bone shows that Lucy and her kind had given up life in trees.
Dr. WARD: If they went in the trees they didn't do it much better than you or I would.
JOYCE: But is one bone enough to prove that? William Jungers, for one, says no. Sure, Lucy's kin had at least a partial arch and could walk. But the new bone doesn't prove that the crucial inside of the arch, the nave of the foot cathedral, if you will, was like ours. Or the big toe or other foot parts. And he says it doesn't prove that Australopithecus had swapped trees for terra firma.
Dr. JUNGERS: Now, if you were betting a modern human and an australopithecine in a climbing contest, let me tell where to put your money.
JOYCE: Jungers and other experts say it will take more bones to decide if this one really rewrites history or is just another fossil footnote.
Christopher Joyce, NPR News.
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