Australopithecus is a genus of hominin that includes the ancestors of all modern humans and which emerged in Africa during the Late Pliocene, some 4.2 million years. The first example consisted of fossilized parts of the skull of a small primate and were discovered by workmen in a lime quarry at Taung, South Africa in 1924. These were then examined by Raymond Dart, an Australian anatomist working at the University of Witwatersrand who was able to ascertain by the structure of the base of the skull that he was dealing with a bipedal primate with a brain about the size of a chimp. He named it Australopithecus africanus, “the Southern Ape from Africa”. 

Up until then it was generally assumed the human beings had evolved in Asia where the fossils of Homo erectus were first discovered, so finding an earlier representative of the hominin line in Africa was quite a shock to the scientific community. They had also taken it for granted that the traits defining what it is to be ‘humanity’— large brains, an upright posture and the manufacture of tools—came as a package. Now they were confronted by a hominin that walked on its hind legs yet had a relatively tiny brain.

Since then, several kindred species have been found in different parts of the continent (although none outside Africa). It has become clear since the discovery of ‘Lucy’ (A. afarensis) who dates to about 3.5 million BP, that the genus originated in East Africa where its precursors have been found.

Early on it was recognized that there were at least two australopithecine lineages, one described as ‘gracile’ and the other ‘robust’. Many scholars assign the latter to a separate genus (Paranthropus) but there is no consensus so far. It is clear from modern dating methods, that the robust lineage is later and contemporary with the earliest human species such as Homo habilis. In the final years of the 20th century, two more genera, Ardipithecus and Orrorin, both of which are earlier than Australopithecus, have been identified and have both been classified as Australopithecina. No doubt many further discoveries await.

Perhaps the thorniest problem when it comes to constructing a taxonomy for any early hominins is the scattered nature of the evidence. The overwhelming majority of the fossils come from very specific geographical regions of Africa—the Rift Valley of East Africa and the limestone caves of the South African Highveld. Conditions for preservation are much better there than in the rest of the continent—much of which is covered by jungle or vast tracts of desert sand—and the political situation has been generally more stable. For these reasons, establishing direct links between species in different regions is almost impossible. Even in regions where the fossils survive and are reasonably accessible, the remains are rarely found in situ and undisturbed. The activities of predators and scavengers and the forces of erosion ensured they were most often broken and well-scattered. Consequently, it is very difficult to decide whether or not a particular bit of bone belongs to the same species as another. Needless to say, this is the subject of warm discussions in the academic community.

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