One cannot overemphasize the role of bipedalism
in hominid development. It stands as perhaps the salient point that differentiates the
forebears of man from other primates. This unique ability freed the hands for myriad
possibilities -- carrying, tool-making, intricate manipulations. From this single
development, in fact, stems all modern technology.
(From Mary Leakey, "Footprints in the Ashes of Time." National
Geographic, April 1979)