Australopithecus was a genus of hominids that evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct 2 million years ago. During this time period various different forms of australopiths existed, including Australopithecus anamensis, A. afarensis, A. sediba, and A. africanus. There is still some debate amongst academics whether certain African hominid species of this time, such as A. robustus and A. boisei constitute members of the same genus; if so, they would be considered to be robust australopiths whilst the others would be considered gracile australopiths. However, if these species do indeed constitute their own genus, then they may be given their own name, the Paranthropus.
It is widely held by archaeologists and palaeontologists that the australopithecus played a significant part in human evolution and it was one of the australopith species that eventually evolved into the Homo genus in Africa around 2 million years ago, which contained within it species like Homo habilis, H. ergaster and eventually the modern human species, H. sapiens sapiens.
The brains of most species of Australopithecus were roughly 35% of the size of that of a modern human brain. Most species of Australopithecus were diminutive and gracile, usually standing between 1.2 to 1.4 m tall (approx. 4 to 4.5 feet). In several variations of Australopithecus there is a considerable degree of sexual dimorphism, in this case males are larger than females. Modern hominids do not appear to display sexual dimorphism to the same degree — particularly, modern humans display a low degree of sexual dimorphism, with males being only 15% larger than females, on average. In Australopithecus, however, males can be up to 50% larger than females. New research suggests that sexual dimorphism may be less pronounced than this, but there is still debate on the subject.