Australopithecus africanus

This species was the first of our pre-human ancestors to be discovered, but was initially rejected from our family tree because of its small brain. This opinion changed when new evidence showed this species had many features intermediate between apes and humans.

Background of discovery

Age

This species lived between 3.2 and 2 million years ago.

Important fossil discoveries

In 1924, a fossil was rescued from a limestone quarry at Taung in South Africa and sent to Australian, Raymond Dart who was a Professor of Anatomy in nearby Johannesburg. The now-famous Taung Child skull had a mixture of human-like and ape-like features. Dart believed it to be an early ancestor of humans and in 1925 he gave his ‘man-ape’ a new species name, Australopithecus africanus.

Dart had difficulty convincing other scientists that this was a human ancestor, partly because at the time, many believed human ancestors had large brains and ape-like jaws whereas the Taung Child had the opposite set of features. Acceptance only arose in the late 1940s after Robert Broom’s discoveries of more fossils including those of adults. Since then, many hundreds of Australopithecus africanus fossils have been found in South Africa.

Key specimens:

• Sts 14: a partial skeleton discovered in1947 by Robert Broom and John Robinson in Sterkfontein, South Africa. The shape of this pelvis proved Australopithecus africanus was able to walk upright on two legs. The spine has six lumbar vertebrae in the lower back. This is a human-like rather than an ape-like feature as modern humans sometimes have six but usually have five lumbar vertebrae whereas modern African apes have five or less.
• MLD 2: a lower jaw from an adolescent discovered in Makapansgat, South Africa
• Taung Child: a partial skull and brain endocast discovered in 1924 in Taung, South Africa. This 2.3 million-year-old skull of a young child is the ‘type specimen’ or official representative of this species. It was the first fossil of a human ancestor ever found in Africa and was also the first to be classified in the genus Australopithecus. We know this individual was a young child because its first molar teeth were in the process of erupting from the jaw.
• Sts 71: a 2.5 million-year-old partial skull discovered in1947 by Robert Broom and John Robinson in Sterkfontein, South Africa. The robust features of this skull indicate it was an adult male.
• ‘Mrs Ples’ or Sts 5: this 2.5 million-year-old skull discovered in 1947 by Robert Broom and John Robinson in Sterkfontein, South Africa. The skull was nicknamed ‘Mrs Ples’ because it was originally considered to be an adult female from the genus Plesianthropus. Later, it was decided that the skull was actually an Australopithecus africanus individual and there is also some debate about whether this skull was that of a female or male.

Malapa hominins

Fossils from two individuals were recovered in 2008 and announced as a new species Australopithecus sediba in 2010. More fossils are in the process of being excavated. Many other palaeontologists consider the ‘A. sediba’ fossils to be a chronospecies of A. africanus – meaning that the slight anatomical differences between the new fossils and A. africanus are due to changes over time within a species rather than them being from different species. This view makes the fossils merely an interesting side branch of our family tree but does extend the time range for A. africanus by almost half a million years

Key specimens are the type specimen Malapa Hominin 1 (MH1), which is considered to be a juvenile and is represented by a partial cranium (UW 88-50), partial lower jaw (UW88-8) and postcranial elements including a right clavicle (UW 88-1); and Malapa Hominin 2 (MH2), a probable female adult represented by partial lower jaw (UW 88-54), isolated teeth from the lower jaw (UW 88-54) and some partial postcranial elements including most of the right arm, ankle and knee joints and bits of the pelvis and shoulder blade. MH2 is the species paratype (a specimen other than a type specimen that is used for the original description of a taxonomic group).

Distribution

All known specimens have been found at various locations in South Africa

What the name means

Australopithecus, means ‘southern ape’. It is based on ‘australo’, a Latin word meaning ‘southern’ and ‘pithecus’, a Greek word meaning ‘ape’. The name was originally created just for this species found in South Africa but several closely related species now share the same genus name.

The word africanus is a Latinised form of the word ‘Africa’ and indicates the continent where this species was found.

Relationships with other species

Australopithecus africanus was once considered to be a direct ancestor of modern humans but new finds have challenged this position. Many scientists now believe this species represents a side branch in our evolutionary family tree but there is disagreement about its exact relationship to other species.

Many of the fossils found at South African sites in the 1930s and 1940s were given separate names, such as Australopithecus transvaalensis, Plesianthropus transvaalensis and Australopithecus prometheus. These are all now recognised as belonging to the same species, Australopithecus africanus.

Fossils discovered in Malapa, South Africa, in 2008 were announced as a new species Australopithecus sediba in 2010, but many other palaeontologists consider the fossils to be a chronospecies of A. africanus – meaning that the slight anatomical differences between the new fossils and A. africanus are due to changes over time within a species rather than them being from different species. This would extend the time range for A. africanus by almost half a million years.

The dental arcade is the shape made by the rows of teeth in the upper jaw. This illustration shows the difference between the dental arcade of an ape, Australopithecus africanus and modern human, Homo sapiens.

Key physical features

Body size and shape

• females grew to about 110 centimetres in height and males were slightly taller at about 135 centimetres
• ape-like features included a cone-shaped rib cage and relatively long arms

Brain:

• averaged approximately 480 cubic centimetres. This was small but still relatively large when compared with a modern chimpanzee’s brain.

Skull:

• compared with the earlier species, Australopithecus afarensis, the skull showed some slightly more human-like features such as a smaller brow ridge and a slightly arched (rather than flat) forehead area.
• like all human ancestors, the spinal cord emerged from the central part of the base of the skull rather than from the back.

Jaws and teeth:

• jaws and teeth were intermediate between those of humans and apes and those of earlier species, such as Australopithecus afarensis
• the canine and incisor teeth had become shorter and smaller
• a gap (diastema) between the canines and adjacent teeth was rare
• premolar teeth and molar teeth were all quite large

Limbs:

• leg and foot bones indicate that this species had the ability to walk on two legs.
• they also indicate some ape-like features including slightly curved finger and toe bones and arms that were quite long, although not longer than their legs.

Pelvis:

• was fully adapted for walking on two legs but compared with those of modern humans it was less rounded, had a narrower birth canal, and was not specialised for a striding gait.

Lifestyle

Culture

This species probably used simple tools such as sticks found in the immediate surroundings and scavenged animal bones. Stones may also have been used as tools, however, there is no evidence that these stones were shaped or modified.

Environment and diet

Over 2.5 million years ago, this species occupied an environment in South Africa in which there was a mixture of woodland and savannah grassland. After 2.5 million years ago, the climate became drier and savannah grasslands spread.

Analysis of tooth wear patterns suggests that Australopithecus africanus had a diet that included fruit and leaves. Chemical analysis of the teeth also suggests that some meat was included in the diet but not in significant amounts. It is likely that they may have scavenged for meat rather than hunted.