The fossil skeletons of Au. sediba from Malapa cave are so complete that scientists can see what entire skeletons looked like near the time when Homo evolved. Details of the teeth, the length of the arms and legs, and the narrow upper chest resemble earlier Australopithecus, while other tooth traits and the broad lower chest resemble humans. These links indicate that Au. sediba may reveal information about the origins and ancestor of the genus Homo. Functional changes in the pelvis of Au. sediba point to the evolution of upright walking, while other parts of the skeleton retain features found in other australopithecines. Measurements of the strength of the humerus and femur show that Au. sediba had a more human-like pattern of locomotion than a fossil attributed to Homo habilis. These features suggest that Au. sediba walked upright on a regular basis and that changes in the pelvis occurred before other changes in the body that are found in later specimens of Homo. The Australopithecus sediba skull has several derived features, such as relatively small premolars and molars, and facial features that are more similar to those in Homo. However, despite these changes in the pelvis and skull, other parts of Au. sediba skeleton shows a body similar to that of other australopithecines with long upper limbs and a small cranial capacity. The fossils also show that changes in the pelvis and the dentition occurred before changes in limb proportions or cranial capacity.
The combination of primitive and derived traits in Australopithecus sediba shows part of the transition from a form adapted to partial arboreality to one primarily adapted to bipedal walking. but the legs and feet point to a previously unknown way of walking upright. With each step, Australopithecus sediba turned its foot inward with its weight focused on the outer edge of the foot. This odd way of striding may mean that upright walking evolved on more than one path during human evolution.