Fossil suggests that Lucy had first modern human foot.
Lucy's feet were made for walking. That's the word from a team of researchers who got a first look at a foot bone from this human relative who lived 3 million or more years ago, and concluded this ancestor was fully comfortable with life on the ground, rather than the trees.
Carol Ward of the University of Missouri, and colleagues, report in Friday's journal Science that the discovery shows that ancient Australopithecus afarensis had feet similar to modern humans. The famous fossil Lucy is the poster girl for her group of ancient hominins. No foot bones were found with her skeleton, so researchers have puzzled over whether she walked like modern people or was a blend of ground- and tree-dweller.
The new discovery shows these relatives "were fully humanlike and committed to life on the ground," Ward said. "It lays to rest the idea that they were a compromise."
The new bone, discovered with other A. afarensis bones at Hadar, Ethiopia, is a metatarsal, one of the long bones connecting the toes to the base of the foot. It shows that Lucy's kin had arches stiffening their feet like modern people, as opposed to apes whose feet are more flexible for grasping tree branches. This was an important step in evolution, Ward said. "This shows our early ancestor walked like we would walk. They were not shuffling, they were walking upright, which is a key feature of our branch of the family tree."
Ward, a professor of integrative anatomy, said that the discovery "affects much of what we know about them, from where they lived to what they ate and how they avoided predators." She said, "The development of arched feet was a fundamental shift toward the human condition, because it meant giving up the ability to use the big toe for grasping branches, signaling that our ancestors had finally abandoned life in the trees in favor of life on the ground."
Richard Potts, director of the human origins program at the Smithsonian's National Museum of Natural History who was not part of the team, said it didn't meant that A. afarensis didn't climb trees. He said it was probably very adaptable. He called the report "an impressive paper for just one bone." He said, "Every once in a while you do get one piece of the puzzle that helps you fill in something. This bone really fills in a missing piece."