Australopithecus — Early bipedal hominins of Africa

Physical characteristics

Australopithecus species show a mosaic of traits. Skeletal features of the pelvis, femur and knee indicate habitual bipedalism, though some aspects of the shoulder, arm proportions and curved finger bones suggest retained climbing abilities. Cranial capacity was small compared with later Homo, often similar in size to modern great apes rather than to modern humans. Dental and jaw anatomy varies, but many species have relatively large molars and thick enamel, implying a diet that could include tough, abrasive foods as well as fruit and other plant matter. Examples of important fossil material and sites are available in regional collections East African sites and in older literature about early discoveries early fossils.

Classification and major forms

The genus historically included a variety of species that paleoanthropologists group, for convenience, as gracile and robust australopithecines. The gracile forms (for example, A. afarensis and A. africanus) tend to have more lightly built faces and teeth, while the so-called robust forms possess larger chewing apparatus, flared cheekbones and sometimes sagittal crests. Some researchers place the robust forms in a separate genus, Paranthropus, while others retain them in Australopithecus; this debate reflects differing interpretations of morphology and ancestry. Well-known specimens that illustrate this diversity include fossils described in early twentieth-century work such as the Taung Child and later finds including the partial skeleton nicknamed Lucy and the Laetoli footprint-bearing deposits Taung Child, Laetoli footprints.

History of discovery and research

The first widely reported australopithecine was the Taung Child, a juvenile skull described by Raymond Dart in 1925, a discovery that initially provoked controversy but ultimately transformed ideas about human origins. Subsequent fieldwork through the mid- and late twentieth century expanded the record with additional species, better-preserved skeletons and trace fossils. Important fossils have come from sites in East and southern Africa and have been discussed in many regional and historical syntheses Raymond Dart, African origins research. Ancient dates and branching patterns are refined as new finds and dating methods appear; splits between the human lineage and other apes are commonly placed earlier than most australopithecine fossils, likely several million years before the youngest Australopithecus remains.

Significance and open questions

Australopithecus is central to understanding the sequence that led to Homo: evidence suggests that habitual bipedalism evolved before the substantial increase in brain size that characterizes our genus. Researchers continue to debate which australopithecine species, if any, is directly ancestral to Homo, how many species should be recognized, and how to interpret variation in diet, locomotion and social behavior from fragmentary remains. For the viewpoint that Australopithecus gave rise to Homo, see general treatments of the transition to our genus Homo ancestry. Distinctions between gracile and robust forms are further discussed in specialist reviews gracile group and comparative treatments of Paranthropus robust group.

Further reading and resources

• Introductory overview
• Hominin taxonomy
• Relationship to modern humans
• Taung Child details
• History of discovery
• East African fossil sites
• Earliest specimens
• Laetoli footprints
• Transition to Homo
• Gracile australopithecines
• Paranthropus and robust forms
• Regional surveys of African prehistory