One of the earliest human ancestors had human-like foot arches that would have allowed it to walk effectively on two legs. The finding may help to resolve the debate about whether this species, Australopithecus afarensis, was completely adapted to terrestrial bipedalism or retained the ape-like ability to climb in the trees.
Carol Ward at the University of Missouri in Columbia and her team analysed a fossilized bone about 3.2 million years old from Ethiopia. The fossil, the fourth metatarsal, is one of the bones that makes up the mid-foot. In flat-footed, tree-climbing chimpanzees, the bone lies flat against the ground, whereas in humans it is twisted and angled — an indicator of stiff, arched feet well adapted for walking with a human-like stride. The A. afarensis bone was twisted and angled similarly to its modern human equivalent.
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Bones made for walking. Nature 470, 309 (2011). https://doi.org/10.1038/470309b
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DOI: https://doi.org/10.1038/470309b
