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Scientists have discovered the oldest skeleton of a human ancestor—a small-brained, 110-pound female Ardipithecus ramidus, nicknamed Ardi. She lived in what is now Ethiopia 4.4 million years ago, making her more than a million years older than Lucy, the previous holder of the oldest hominid skeleton. The difference between Ardi and Lucy is that the latter is a bipedal hominid, while Ardi was able to both walk on two legs and use four limbs when climbing in trees—perhaps providing insight into the ape-to-human transition. According to conventional wisdom, our lineage became bipedal when they moved from the forest to the grasslands, and Ardi lived in a woodland environment.