What were some important changes the skeleton of australopithecines that reflect bipedal stance and locomotion

Answer 1

A. afarensis, a lineage of relatively terrestrial pongids who were habitual bipeds but may have slept in trees, is a representative of an early human adaptive radiation. Their brains were small (350 cm3), but the pelvis and knee are configured like bipedal humans rather than quadrupedal pongids. Limb proportions are human (Lovejoy (1993). The A afarensis great toe (metatarsal I), which is opposable in pongids, is aligned with the other toes, an adaptation for bipedal walking (Latimer and Lovejoy, 1990a, 1990b). Bipedal locomotion is no longer the facultative bipedalism seen in extant pongids, it is obligate bipedalism - the spinal column, arms, pelvis, legs, and feet are modified to make quadrupedalism difficult. Body size is extremely dimorphic -- males weighing over 60 kg and females about 30 kg. They were apparently part of an adaptive radiation of Australopithecines into the terrestrial pongid niche, a radiation that produced at least two other Australopithecine lineages.


A third lineage derived from this adaptive radiation of terrestrial pongids is characterized by retention of a rather primitive (chimpanzee-like) face and an expanding cranial capacity. The earliest representatives are Homo habilis, thought to be a lineage of bipedal pongids that progressively emphasized tool use as evidenced by discarded tools that litter their landscape. Since Australopithecines overlap H. habilis in time, there is no way of knowing whether Homo was the only tool maker, but it is clear in later Homo sites that tool manufacture and use was a fundamental element of subsistence activities, and is an important character in the second human adaptive radiation.

Answer 2

Growth of the pelvis and adjustment of the pelvic tilt, which allowed the creature to sustain its weight and keep its spine erect, Thicker leg bones to adjust to the shock of bipedal locomotion, change in skull size, especially in the forhead area which allowed for forward motion while erect, but still kept the creature from pitching forward.

Answer 3

The width of the pelvis as relates to the femurs decreased to decrease "waddling" as well.