Lufengpithecus inner ear provides evidence of a common locomotor repertoire ancestral to human bipedalism

Various lines of evidence have been used to infer the origin of human biped-alism, but the paucity of hominoid postcranial fossils and the diversity of in-ferred locomotor modes have tended to confound the reconstruction ofancestral morphotypes. Examination of the bony labyrinth morphology ofthe inner ear of extinct and living hominoids provides independent evidencefor inferring the evolution of hominoid locomotor patterns. New computedtomography data and morphometric analyses of the Late Miocene apeLu-fengpithecusindicate that it and other stem great apes possess labyrinthssimilar to one another and show that hominoids initially evolved from a po-sitional repertoire that included orthogrady, below-branch forelimb suspen-sion and progression, above-branch bipedalism, climbing, clambering, andleaping (hylobatid-like) to one that comprised above-branch quadrupedal-ism, below-branch forelimb suspension, vertical climbing, limited leaping,terrestrial quadrupedal running and walking, possibly with knuckle walking,and short bouts of bipedalism (chimpanzee-like). The bony labyrinthmorphology ofLufengpithecusindicates that it probably conforms moreclosely to the last common ancestors of crown hominoids and hominidsin its locomotor behavior than do other Miocene hominoids. Human biped-alism evolved from this common archetypalLufengpithecus-like locomotorrepertoire. The low evolutionary rate of semicircular canal morphology sug-gests thatLufengpithecusexperienced a relative stasis in locomotorbehavior, probably due to the uplift of the Tibetan Plateau, which createda stable environment in the Miocene of southwestern China.