Model of 'Lucy', a young female Australopithecus afarensis hominid. The model was created from a cast of Lucy's bones, and exhibited at the Kenya National Museum, Nairobi, Kenya. The fossil bones are around 3.3 million years old, and are generally thought to represent the earliest known ancestor of humans. The skeleton was found in the Afar region of Ethiopia in 1974. A. afarensis lived between 3.9 and 2.9 million years ago. The structure of the pelvis and legs suggests that it was bipedal. A set of fossilized footprints found in Laetoli, Tanzania, that date from around 3.5 million years ago also provide evidence for bipedalism.