Shoulder mobility would support suspensory locomotion behaviors which are present in human bipedalism. Common chimpanzees, bonobos, gibbons and baboons exhibit forms of bipedalism. Like other tetanurans, megalosaurids are carnivorous theropods characterized by large size and bipedalism. It is unclear which evolved first; sociality, bipedalism, or birth attendance. Injured chimpanzees and bonobos have been capable of sustained bipedalism. There are several hypothesizes for how early brachiating primates may have transitioned into bipedalism. Lovejoy theorizes that the evolution of bipedalism was linked to monogamy. Humans have evolved both bipedalism and large brain size. Biomechanical analysis also suggests it had adaptations to bipedalism. This shows that "A. sediba" may have practiced a unique combination of bipedalism and arboreality. Fossil evidence such as this makes it clear that bipedalism far predated large brains. Shoulder stability would decrease with the evolution of bipedalism. Subsequently, older "Ardipithecus ramidus" fossils were found with features that suggest bipedalism. Day (1986) emphasized three major pressures that drove evolution of bipedalism 1.food acquisition 2. This is because their femurs are not adapted for bipedalism.