"Lucy" is the name for the 40% complete Australopithecus afarensis skeleton unearthed in 1974 at Hadar in the Awash Valley of Ethiopia. The bones are around 3.3 million years old, and are generally thought to represent the earliest known ancestor of humans. A. afarensis lived between 3.9 and 2.9 million years ago. It is thought to have been bipedal, evidence coming from the structure of the pelvis and legs, and from a set of fossilized footprints found in Laetoli, Tanzania, that date from around 3.5 million years ago. California Academy of Sciences.