australopithecine

Australopithecines are a group of extinct hominins that lived in Africa between about 4 and 2 million years ago. The term is informal and includes several species assigned to the genus Australopithecus, as well as closely related forms such as Kenyanthropus. They are among the earliest human ancestors known to show clear bipedal locomotion.

Anatomically, australopithecines had small brain sizes, averaging about 380–550 cubic centimeters, much smaller than later Homo. Their faces were prognathic, with large cheek teeth. They possessed skeletal adaptations for upright walking, including a broader pelvis and knee alignment suited to bipedal gait, yet they retained longer arms and curved fingers indicating some arboreal activity.

Key species include Australopithecus afarensis (4.2–3.0 million years ago), known from fossils such as Lucy at Hadar, Ethiopia; A. africanus (3.0–2.4 million years ago) from Taung and Sterkfontein in South Africa; A. anamensis (4.1–3.9 million years ago) from eastern Africa; and A. sediba (about 2 million years ago) from Malapa, South Africa. Some researchers also refer to additional forms such as Kenyanthropus.

Diet and behavior were diverse and probably omnivorous, including fruits, seeds, and occasional meat. Evidence for tool use is limited but some later australopithecines, such as A. garhi, have been associated with cut-marked bones, suggesting possible opportunistic tool use and meat processing.

Taxonomically, australopithecines are a paraphyletic grouping rather than a single, natural clade. They are important for understanding human evolution because they document early, habitual bipedalism and a stage between the earliest hominins and the emergence of the genus Homo.