Abstract Lucy's pelvic inlet is extremely wide, particularly in relation to body size. This width, when combined with the horizontal rotation of the pelvis, minimizes the vertical displacement of the center of mass during bipedal walking. A different manner of reducing this vertical displacement and of diminishing its undesirable effects is the elongation of the lower limbs. Adoption of this strategy by later hominids presumably permitted the relative narrowing of the inlet and thus of the distance between the hip joints. Lucy's pelvis, there-fore, does not represent simply an intermediate stage between a chimpanzee-like hominoid and Homo sapiens, nor is it essentially a modern human pelvis. Although clearly bipedal and highly terrestrial, Lucy evidently achieved this mode of locomotion through a solution all her own.