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Where Lived: Eastern Africa (Middle Awash and Gona, Ethiopia)
When Lived: About 4.4 million years ago
Ardipithecus ramidus was first reported in 1994; in 2009, scientists announced a partial skeleton, nicknamed ‘Ardi’. The foot bones in this skeleton indicate a divergent large toe combined with a rigid foot – it's still unclear what this means concerning bipedal behavior. The pelvis, reconstructed from a crushed specimen, is said to show adaptations that combine tree-climbing and bipedal activity. The discoverers argue that the ‘Ardi’ skeleton reflects a human-African ape common ancestor that was not chimpanzee-like. A good sample of canine teeth of this species indicates very little difference in size between males and females in this species.
Ardi’s fossils were found alongside faunal remains indicating she lived in a wooded environment. This contradicts the open savanna theory for the origin of bipedalism, which states that humans learned to walk upright as climates became drier and environments became more open and grassy.