Lucy may well be the world's most famous fossil hominid. She is the best-known specimen of the species Australopithecus afarensis, and her partial skeleton, found in 1974, revealed that she and her kin could walk upright.

But because of a lack of foot bone specimens, scientists have long debated how well she walked that is, whether A. afarensis also used a grasping movement with the feet, as apes do when they grab tree branches.

Now, a fossilized foot bone from Hadar, Ethiopia, reveals that A. afarensis had arched feet, as do modern humans, and was fully committed to walking upright. The species lived between 3.7 million and 2.9 million years ago.

Researchers from the University of Missouri and Arizona State University report these findings in the journal Science.

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