Australopithecus africanus


Australopithecus africanus

Taxobox | name = "Australopithecus africanus"
fossil_range = Pliocene


image_width = 250px
image_caption= Replica of the Mrs. Ples skull
regnum = Animalia
phylum = Chordata
classis = Mammalia
ordo = Primates
familia = Hominidae
genus = †"Australopithecus"
species = †"A. africanus"
binomial = †"Australopithecus africanus"
binomial_authority = Dart, 1925

"Australopithecus africanus" was an early hominid, an australopithecine, who lived between 2-3 million years ago in the Pliocene. [ [http://www.mnh.si.edu/anthro/humanorigins/ha/a_tree.html Human Ancestors Hall: Tree ] ] 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). [http://www.archaeologyinfo.com/australopithecusafricanus.htm Australopithecus africanus ] ]

Famous fossils

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. [ [http://www.press.uchicago.edu/Misc/Chicago/284158_brain.html Raymond Dart and our African origins ] ] 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, 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.

Mrs. Ples

Dart's theory was supported by Robert Broom. [http://www.anth.ucsb.edu/faculty/walker/classes/anth121/121australopithecus.pdf Primate Origins ] ] 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, [ [http://archaeology.about.com/od/rterms/g/robinsonjt.htm John T. Robinson ] ] 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".

Morphology and interpretations

Like "A. afarensis", "A. africanus" the South African counterpart was generally similar in many traits, a bipedal hominid 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.

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. "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. [ [http://www.sciencedaily.com/releases/2007/10/071025160653.htm New Ideas About Human Migration From Asia To Americas ] ] 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. [ [http://www.apologeticspress.org/articles/127 Apologetics Press - Human Evolution and the “Record of the Rocks” ] ]

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. [The Independent's article [http://news.independent.co.uk/sci_tech/article3247561.ece A pregnant woman's spine is her flexible friend] , by Steve Connor from The Independent (Published: 13 December 2007) quoting [http://www.utexas.edu/cola/depts/anthropology/faculty/profiles/Shapiro/Liza/ Shapiro, Liza] , University of Texas at Austin Dept. of Anthropology about her article, Whitcome, et al., [http://www.nature.com/news/2007/071212/full/news.2007.374.html Nature advance online publication, doi:10.1038/nature06342 (2007)] . ] [ [http://news.nationalgeographic.com/news/2007/12/071212-pregnancy-tips_2.html 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.]

ee also

* Cranial capacity
* List of human fossils
* List of fossil sites "(with link directory)"
* List of hominina (hominid) fossils "(with images)"
* Human evolution

References

External links

* [http://www.mnsu.edu/emuseum/biology/humanevolution/africanus.html MNSU]
* [http://www.mnh.si.edu/anthro/humanorigins/ha/afri.html Smithsonian]
* [http://www.handprint.com/LS/ANC/evol.html Handprint]
* [http://www.maropeng.co.za Maropeng - The Cradle of Humankind] Official Website
* [http://whc.unesco.org/pg.cfm?cid=31&id_site=915 UNESCO - Fossil Hominid Sites of Sterkfontein, Swartkrans, Kromdraai, and Environs]


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