Australopithecus africanus

Australopithecus africanus (Plesianthropus transvaalensis holotype).jpg

Australopithecus africanus is an extinct (fossil) species of the australopithecines, the first of an early ape-form species to be classified as hominin (in 1924). Recently it was dated as living between 3.3 and 2.1 million years ago, or in the late Pliocene and early Pleistocene times; it is debated as being a direct ancestor of modern humans.[2] A. africanus was of slender, or gracile, build and has been found only in southern Africa at four sites: Taung (1924), Sterkfontein (1935), Makapansgat (1948) and Gladysvale (1992).[1]

Raymond Dart, then the head of the department of anatomy at the University of the Witwatersrand in Johannesburg, South Africa, became interested in fossils found at a limestone quarry at Taung near Kimberley, South Africa in 1924.[3][4] The most promising of these was a skull of an odd ape-like creature presenting human traits at the eye orbits, teeth, and, most importantly, the hole at the base of the skull over the spinal column (the foramen magnum); its placement indicated a human-like upright posture and implied a high probability that this hominid-to-hominin primate had achieved bipedal, as opposed to quadrupedal locomotion. Dart assigned the specimen the name Australopithecus africanus ("southern ape of Africa");[1] it was also dubbed "the Taung child".

This was the first time the word "ape" (-pithecus) was formally assigned to any hominin, which, in effect, formally declared humans as descended from apes. Dart theorized the Taung child skull must represent an intermediate species between apes and humans. But his claim was rejected by the scientific community, generally in deference to the broadly-held idea (idée fixe) that the early development of the line to humans required that a large cranium ("big brain") would precede bipedal locomotion; (see below, Mrs. Ples: cranial capacity).[1] And the rejection was buttressed by the widespread belief then, especially in British academia, that the Piltdown Man recently found in England was the likely progenitor of the human lineage. (Piltdown man was later exposed as a forgery.)

Sir Arthur Keith was an anatomist and anthropologist fellow in 1924, and a scientist whose personal prejudice looked to Europe—not to Asia or Africa—as the place where the early hominins would be shown to have emerged.[5] He dismissed Dart's claim, suggesting instead that the Taung child skull belonged to a young ape, most likely an infant gorilla or chimpanzee.[6][7] Keith's persistence in denouncing the possibility of Australopithecus while justifying the plausibility of Piltdown man was instrumental in binding the two issues inextricably together for over a generation.

Keith immersed himself in defending the Piltdown man and his reputation suffered greatly after the hoax was exposed in 1953. Phillip Tobias, in a lengthy essay published in Current Anthropology in 1992, detailed the history of the investigation of the hoax. He presented argument that implicated the motive of Keith's adamant and continual opposition to Australopithecus, to wit: if Australopithecus was a hominin ancestor, then Piltdown man could not have been and its bona fides would have been suspect and called out for formal investigation. As part of the essay Tobias debated the inconsistencies in Keith's statements and actions with contemporary members of the science community.[8]

Keith's persistent animus towards the Taung child discovery caused serious consequences; from Dart's announcement in 1924, it took nearly 30 years before the inevitable methods of science revealed the Piltdown man hoax and supported the validity of the claims (of hominin status) for Australopithecus.

Dart's theory—that the skull known as the Taung child was a human ancestor—was supported by Robert Broom, a paleontologist with the Transvaal Museum of natural history in Pretoria.[9] In 1936, the Sterkfontein caves yielded the first adult australopithecine, substantially strengthening Dart's claim for Broom. Later, Broom classified an adult endocranial cast having a brain capacity of 485 cc (found by G. W. Barlow) as Plesianthropus transvaalensis (near-man from Transvaal). In April 1947, while blasting at Sterkfontein, he and John T. Robinson discovered a skull belonging to a middle-aged female[10] (catalogue number STS 5) which he also classified as Plesianthropus transvaalensis (it was dubbed "Mrs. Ples" by Broom's young coworkers although the skull is now thought to have belonged to a young male). Both fossils were later classified as Australopithecus africanus.

This page was last edited on 20 June 2018, at 05:37 (UTC).
Reference: under CC BY-SA license.

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