Australopithecus africanus
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| Australopithecus africanus Fossil range: Pliocene |
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 STS 5 "Mrs. Ples"
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| †Australopithecus africanus Dart, 1925 [1] |
Australopithecus africanus was an early hominid, an australopithecine, who lived between 2-3 million years ago in the Pliocene.[2] In common with the older Australopithecus afarensis, A. africanus was slenderly built, or gracile, and was thought to have been a direct ancestor of modern humans. Fossil remains indicate that A. africanus was significantly more like modern humans than A. afarensis, with a more human-like cranium permitting a larger brain and more humanoid facial features. A. africanus has been found at only four sites in southern Africa - Taung (1924), Sterkfontein (1935), Makapansgat (1948) and Gladysvale (1992).[1]
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[edit] Famous fossils
[edit] Taung Child
Raymond Dart was at Taung near Kimberley, South Africa in 1924 when one of his colleagues spotted a few bone fragments and the cranium on the desk of a lime worker.[3] The skull seemed like an odd ape creature sharing human traits such as eye orbits, teeth, and, most importantly, the hole at the base of the skull over the spinal column (the foramen magnum) indicating a human-like posture. Dart assigned the specimen the name Australopithecus africanus ("southern ape of Africa"). This was the first time the word Australopithecus was assigned to any hominid. Dart claimed that the skull must have been an intermediate species between ape and humans, but his claim about the Taung Child was rejected by the scientific community at the time due to the belief that a large cranial capacity must precede bipedal locomotion,[1] this was exacerbated by the widespread acceptance of the Piltdown Man. Sir Arthur Keith, a fellow anatomist and anthropologist, suggested that the skull belonged to a young ape, most likely from an infant gorilla.
[edit] Mrs. Ples
Dart's theory was supported by Robert Broom.[4] In 1938 Broom classified an adult endocranial cast having a brain capacity of 485 cc, which had been found by G. W. Barlow, as Plesianthropus transvaalensis. On April 17, 1947, Broom and John T. Robinson discovered a skull belonging to a middle-aged female,[5] Sts 5, while blasting at Sterkfontein. Broom classified it also as Plesianthropus transvaalensis, and it was dubbed Mrs. Ples by the press (though the skull is now thought to have belonged to a young male). The lack of facial projection in comparison to apes was noted by Raymond Dart (including from Taung Child), a trait in common with more advanced hominines. Both fossils were later classified as A. africanus.
[edit] Morphology and interpretations
Like A. afarensis, A. africanus the South African counterpart was generally similar in many traits, a bipedal hominin with arms slightly larger than the legs (a physical trait also found in chimpanzees). Despite its slightly more human-like cranial features, seen for example in the craniums Mr. Ples and Sts 71, other more primitive features including ape-like curved fingers for tree climbing are also present.
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Due to other more primitive features visible on A. africanus, some researchers believe the hominin, instead of being a direct ancestor of more modern hominins, evolved into Paranthropus. The one particular robust australopithecine seen as a descendent of A. africanus is Paranthropus robustus. Both P. robustus and A. africanus craniums seem very alike despite the more heavily built features of P. robustus that are adaptations for heavy chewing like a gorilla. A. africanus, on the other hand, had a cranium which quite closely resembled that of a chimp, yet both their brains measure about 400 cc to 500 cc and probably had an ape-like intelligence.[4] A. africanus had a pelvis that was built for slightly better bipedalism than that of A. afarensis.
Charles Darwin suggested that humans had originally evolved from Africa, but during the early 20th century most anthropologists and scientists supported the idea that Asia was the best candidate for human origins.[6] However, the famous Leakey family have argued in favor of the African descent since most hominid discoveries such as the Laetoli footprints were uncovered in Eastern Africa.[7]
[edit] With regards to bipedalism
Recent evidence regarding modern human sexual dimorphism (physical differences between men and women) in the lumbar spine has been seen in pre-modern primates such as A. africanus. This dimorphism has been seen as an evolutionary adaptation of females to better bear lumbar load during pregnancy, an adaptation that non-bipedal primates would not need to make.[8][9]
[edit] See also
- Cranial capacity
- List of human fossils
- List of fossil sites (with link directory)
- List of hominina (hominid) fossils (with images)
- Human evolution
[edit] References
- ^ a b c Australopithecus africanus
- ^ Human Ancestors Hall: Tree
- ^ Raymond Dart and our African origins
- ^ a b Primate Origins
- ^ John T. Robinson
- ^ New Ideas About Human Migration From Asia To Americas
- ^ Apologetics Press - Human Evolution and the “Record of the Rocks”
- ^ The Independent's article A pregnant woman's spine is her flexible friend, by Steve Connor from The Independent (Published: 13 December 2007) quoting Shapiro, Liza, University of Texas at Austin Dept. of Anthropology about her article, Whitcome, et al., Nature advance online publication, doi:10.1038/nature06342 (2007).
- ^ Why Pregnant Women Don't Tip Over. Amitabh Avasthi for National Geographic News, December 12, 2007. This article has good pictures explaining the differences between bipedal and non-bipedal pregnancy loads.
[edit] External links
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