In 1994, Tim White and an international team uncovered a partial female skeleton near Aramis in Ethiopia's Awash Valley. Catalogued as ARA-VP-6/500, the find was published in 2009 after fifteen years of meticulous restoration and assigned to a new species, Ardipithecus ramidus. "Ardi" — "ground" in the Afar language — lived around 4.4 million years ago, more than a million years before Lucy (Australopithecus afarensis).

The importance of Ardi is the opposite of chimp-like: the find upended the long-running assumption that the last common ancestor of humans and chimpanzees would have looked chimp-like. Ardi's hands and feet resemble neither modern chimpanzees nor modern humans; she was a skilled tree-climber, while on the ground she walked upright — though not as fully as Lucy — in a distinctive mosaic of her own. Her pelvis was adapted to bipedal posture; her big toe, however, was still opposable and able to grip branches.

Her habitat overturned another expectation: Ardi lived in a closed woodland ecosystem, not on open savanna. This puts serious pressure on the "savanna hypothesis" that open grassland selected for bipedalism. Ardipithecus shows that the anatomy of modern humans assembled not as a straight ladder but as a mosaic, with traits evolving on their own terms and on different schedules.