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Tuesday, February 15, 2011

Lucy walked like a man

Lucy, the most well known member of the species Australopithecus afarensis, could apparently walk like modern humans. Carol Ward of the University of Missouri and William Kimbel and Donald Johanson from Arizona State University discovered an Australopithecus afarensis foot bone that shows clear evidence that Lucy had an arched foot.

This image shows the position of the fourth metatarsal Australopithecus afarensis (AL 333-160) recovered from Hadar, Ethiopia, in a foot skeleton.

Credit: Carol Ward/University of Missouri

Australopithecus afarensis lived about 3.2 million years ago. Anthropologists knew that the species was bipedal. In fact, much older hominids such as Ardi or Ardipithecus ramidus (4.4 million years ago) were known to have walked upright. However Ardi definitely had chimp-like grasping feet, ill suited for travel over flat ground. Until recently, no one knew what kind of feet Lucy had, and thus what kind of locomotion she could have employed. The discovery of the fourth metatarsal of an Australopithecus afarensis answered that question. With an arched sole and no grasping big toe, Lucy clearly walked upright on the ground like modern humans, rather than across tree branches as Ardi presumably did.

The foot bone was found in Hadar, Ethiopia, at a site referred to as the ‘First Family Site’. This rich site has yielded over 250 Australopithecus afarensis fossil specimens from at least 17 individuals.