Australopithecus Afarensis
Australopithecus afarensis lived between 3.9 and 3.0 million years ago. They are believed to be the most ancient common ancestor, or "stem" species, from which all later hominids sprang.
We know that Australopithecus Afarensis walked upright, as the whole in the spinal cord where the spine goes into the skull, the foramen magnum, is under the skull, so that the head pivots on the spinal column. The leg bones are also thicker than the bones in the arm, and the pelvis is stronger than the shoulders, which implies that weight was placed mainly on the legs, rather than evenly distributed, which it would be if it travelled on all fours.
We also have several clues about the diet of Australopithecus Afarensis. We can tell that there is vegetation in the diet, as the muscles which pull the jaw from side to side are stronger than in carnivores, and the molars are flatter. Australopithecus Afarensis are very similar to ours, so they probably have a varied, omnivorous diet as we do. Sometimes microscopic scratches on the enamel of the teeth can tell us more about the diets of fossilised humans.
Evidence from Lucy and the members of the First Family suggest that "males of the species may have been more robust in stature compared to their female counterparts".
