Australopithecus africanus

The species in brief

Australopithecus africanus (“southern ape of Africa”) was an upright-walking early human relative that lived in the dry, open country of South Africa between about 3.3 and 2.1 million years ago. Its brain, around 450 cubic centimetres, was not much bigger than a chimpanzee’s, but its face was flatter, its canine teeth smaller and its way of getting around more human-like than any living ape’s.

It matters as much for what it did to science as for what it was. When it was first described, in 1925, almost nobody believed that humans began in Africa.

The Taung Child

In 1924 workers were blasting limestone at the Buxton quarry near Taung. Josephine Salmons, a student of the anatomist Raymond Dart at the University of the Witwatersrand in Johannesburg, noticed a fossil baboon skull from the quarry on a director’s mantelpiece, and Dart asked the company to send him any other fossils it found. Late in 1924 two boxes of rock arrived. In one he found a natural cast of the inside of a skull. Dart spent weeks chipping away the stone and uncovered the face and jaw of a small child with a full set of milk teeth and the first adult molars just coming through.

Dart saw something between an ape and a human. The skull’s base was set so that the head sat on top of the spine, as in a person walking upright, and the teeth were small and humanlike. He announced the find in the journal Nature in February 1925, naming it Australopithecus africanus.

Most experts rejected it. At the time they expected humans to have started in Asia or Europe, and to have started with a large brain. The Piltdown forgery, discovered only in 1953, seemed to support that, with its big brain and ape jaw. A South African child with a small brain was dismissed as an ape. Dart’s fossil was not widely accepted until the 1940s and 1950s, when more adults turned up and Piltdown was exposed.

A modern look at the child’s skull gives an age of about three to four years and a small brain of roughly 400 cubic centimetres at death, which would have grown to about 450 to 500. In the 2000s Lee Berger and Ronald McGraw showed that the pattern of damage on the skull and in the eye sockets matches that left by crowned eagles on monkey skulls today. The child was probably killed by an eagle.

Sterkfontein and the cave fossils

Robert Broom, a Scottish doctor and paleontologist, took up the search. At Sterkfontein, near Johannesburg, he found the first adult skull of the species in 1936 and, in 1947 with John Robinson, a very complete one known as Sts 5 and nicknamed “Mrs Ples”. Further species were found in neighbouring caves such as Makapansgat, Gladysvale and later Malapa.

Dating the South African caves is difficult. They are filled with rubble and cave deposits that are hard to date accurately. Current work places africanus at Sterkfontein between about 3.3 and 2.1 million years ago, and the Taung Child at about 2.6 million years. The oldest part of the range is debated, because a nearly complete skeleton called Little Foot (StW 573) from Sterkfontein, found by Ron Clarke from 1994, has been dated to more than 3.6 million years. Clarke places it in a separate species, Australopithecus prometheus, while other researchers think it is africanus or something else. See Sterkfontein.

Body and lifestyle

• Size. About 1.15 to 1.4 m (3 ft 9 in to 4 ft 7 in) tall. Males were bigger than females.
• Walking and climbing. The pelvis, knee and spine show it walked upright. The arms were relatively long and the shoulder suited climbing, so, like A. afarensis, it probably spent time in trees.
• Face and teeth. The face is flatter and the canines smaller than in afarensis. The cheek teeth were large with thick enamel, built for chewing tough plant food.
• Brain. About 450 cubic centimetres on average.
• Diet. The carbon in its teeth shows it ate a mix of tree and shrub plants and grassland foods (including grasses, sedges, or animals that ate them). It probably ate fruit, leaves, seeds, roots and insects, and perhaps some meat.

Where it fits in the family tree

A. africanus is sometimes presented as the link between older apes and the genus Homo, as Broom believed. Today that is less certain. East African species such as afarensis are older and some features of africanus look more like the later robust australopiths. Some researchers think africanus gave rise to Paranthropus robustus. The 2010 discovery of Australopithecus sediba at Malapa, which had both africanus-like and Homo-like features, showed that South Africa held more than one lineage of australopiths about two million years ago. Which of them, if any, leads to us is still open.

Where to see it

The Sterkfontein Caves and the Maropeng visitor centre, both in the Cradle of Humankind World Heritage Site (declared in 1999), are open to the public. Mrs Ples and the Taung Child are kept in South African institutions, and Little Foot is held at the University of the Witwatersrand.

Sources

• Smithsonian National Museum of Natural History, Human Origins Program. Australopithecus africanus.
• Dart, R. A. (1925). Australopithecus africanus: the man-ape of South Africa. Nature 115: 195 to 199.
• Berger, L. R. and McGraw, W. S. (2007). Further evidence for eagle predation of, and feeding damage on, the Taung child. South African Journal of Science 103: 496 to 498.
• Broom, R. and Robinson, J. T. (1947). Further remains of the Sterkfontein ape-man, Plesianthropus. Nature 160: 430 to 431.
• Granger, D. E. and others (2015). New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan. Nature 522: 85 to 88.