How did Australopithecus sediba combine humanlike and apelike features?

Australopithecus sediba is characterized by a unique mosaic of humanlike and apelike features that suggest it was both bipedal and arboreal.12

Key Anatomical Features

• Hand and Wrist: Unlike earlier australopiths, A. sediba possessed shorter fingers and an elongated thumb. This structure likely allowed for both efficient tree climbing and the dexterity required to manipulate or create simple tools.12
• Pelvis: The species displayed a short, broad, and curved pelvis similar to that of the genus Homo, suggesting adaptations for bipedal locomotion that preceded significant brain expansion.2
• Skull and Brain: While the brain size remained similar to other australopiths, the species showed a shift toward a more humanlike frontal lobe, with braincase shapes and olfactory bulb positions resembling those of modern humans.2
• Lower Body: The foot and ankle retained apelike traits, such as a heel adapted for climbing, but also featured a foot arch and a robust Achilles tendon indicative of bipedalism. Similarly, the lumbar vertebrae show a natural curve consistent with human bipedalism alongside structures supporting the strong trunk muscles needed for arboreal movement.2