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Last updated on April 18, 2014 at 17:24 EDT

Australopithecus africanus

Australopithecus africanus was an early hominid, an australopithecine that lived between roughly 3.03 and 2.04 million years ago in the later Pliocene and early Pleistocene. Au. africanus was of slender build and was thought to have been a direct ancestor of modern humans. Fossil remains signify that Au. africanus was considerably more like modern humans that Au. afarensis, with a more human-like cranium permitting a larger brain and more humanoid facial features. This hominid has only been found in four sites in southern Africa – Tuang, Sterkfontein, Makapansgat, and Gladysvale.

A promising fossil of the Tuang site was a skull of an odd ape-creature sharing human characteristics such as eye orbits, teeth, and most importantly, the hole at the base of the skull of the spinal column signifying a human-like posture. Raymond Dart assigned the specimen the name Australopithecus africanus. This was the first time the word Australopitecus was assigned to any hominid. Dart stated that the skull must have been an intermediate species between the ape and the human, but his claim about the Tuang Child was rejected by the scientific community at the time because of the belief that a large cranial capacity must precede bipedal locomotion. This was exacerbated by the widespread acceptance of the Piltdown Man. Sir Arthur Keith, a fellow anatomist and anthropologist, proposed that the skull belonged to a young ape, probably from an infant gorilla. It was not until twenty years later that the public accepted the new genus and that australopithecines were a true member of Homininae.

Much like Au. afarensis, Au. africanus the South African counterpart was over-all similar in many traits, a bipedal hominid with arms slightly larger than the legs. In spite of its slightly more human-like cranial features, other more primitive features, including ape-like curved fingers for tree climbing, are present as well.

Because of other more primitive features that are visible on Au. africanus, some researchers believe the hominin, rather than being a direct ancestor of more modern hominins, evolved into Paranthropus. One robust australopithecine seen as a descendent of Au. africanus is Paranthropus robustus. Both P. robustus and Au. africanus crania appear very alike despite the more heavily built features seen in P. robustus that are adaptations for chewing heavily like a gorilla. Au. africanus, on the other hand, had a cranium which fairly closely resembled that of a chimp, yet both their brains measure about 400 cc to 500 cc and most likely had an ape-like intelligence. Au. africanus had a pelvis that was constructed for slightly better bipedalism than that of Au. afarensis.

Some recent evidence regarding modern human sexual dimorphism in the lumbar spine has been noticed in pre-modern primates such as Au. africanus. This sexual difference has been seen as an evolutionary adaptation of females to better bear lumbar load during their pregnancy, an adaptation that non-bipedal primates wouldn’t need to make.

Image Caption:  Australopithecus africanus – Two views of same specimen formerly named Plesianthropus transvaalensis (holotype). Natural endocranial cast (485 cm3) (Sts 60), articulated with a fragmentary skull still embedded in breccia (TM 1511) wich includes the left maxilla, the orbital area and most of the skull base. Found by G. W. Barlow and described by Robert Broom in 1936. Discovered in South Africa . Collection of the Transvaal Museum, Northern Flagship Institute, Pretoria South Africa. Credit: José Braga;Didier Descouens/Wikipedia (CC BY-SA 3.0)

Australopithecus africanus