The most primitive hominid yet found, this species has more chimpanzee-like features than any other human ancestor. Ardipithecus ramidus may have walked upright. Other fossils discovered with A.

It certainly did in 1976, when paleoanthropologist Andrew Hill and a colleague were tossing elephant dung at each other in Laetoli, a hominid archeological site in Tanzania. As Hill dived out of ...