It was previously thought that Australopithecus afarensis walked in a crouched posture, and on the side of the foot, pushing off the ground with the middle part of the foot, as today's great apes do. We found, however, that the Laetoli prints represented a type of bipedal walking that was fully upright and driven by the front of the foot, particularly the big toe, much like humans today, and quite different to bipedal walking of chimpanzees and other apes.Quite remarkably, we found that some healthy humans produce footprints that are more like those of other apes than the Laetoli prints. The foot function represented by the prints is therefore most likely to be similar to patterns seen in modern-humans. This is important because the development of the features of human foot function helped our ancestors to expand further out of Africa.
Our work demonstrates that many of these features evolved nearly four million years ago in a species that most consider to be partially tree-dwelling. These findings show support for a previous study at Liverpool that showed upright bipedal walking originally evolved in a tree-living ancestor of living great apes and humans.
Australopithecus afarensis, however, was not modern in body proportions of the limbs and torso.The characteristic long-legged, short body form of the modern human allows us to walk and run great distances, even when carrying heavy loads. Australopithecus afarensis had the reverse physical build, short legs and a long body, which makes it probable that it could only walk or run effectively over short distances.