bipedalism a mode of locomotion found in many primates (particularly man) and birds, in which only the hind limbs are used in walking. True bipedalism (i.e. where locomotion is normally bipedal) has required evolutionary changes to the vertebral column and pelvis, with their associated musculature. A principal advantage of bipedalism would seem to be that the forelimbs can become modified for a nonwalking function, e.g. tool handling in man, flight in birds.