Australopithecus

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Related to australopithecine: Australopithecus africanus, Babur, Neanderthal

Australopithecus

(ôstrā'lōpĭth`əkəs, –pəthē`kəs), an extinct hominin genus found in Africa between about 4 and 1 million years ago. At least seven species of australopithecines are now generally recognized, including Australopithecus afarensis, A. africanus, A. bahrelghazali, A. anamensis, A. boisei, A. robustus, and A. aethiopicus. Among their many shared anatomical traits were a fully erect posture and bipedal gait (though the degree to which all the species could comfortably walk upright on the ground is a matter of dispute). The most "primitive" anatomical feature was a small and apelike braincase, comparable in size to those of gorillas and chimpanzees when measured relative to overall body size. Other species have been reported found, including A. garhi in Ethiopia in 1999. There is considerable disagreement among experts on the number of species that should be included within the genus, and two of the seven species listed above—A. bahrelghazali and A. anamensis—are based on very fragmentary remains.

A. afarensis, dating to at least 3.75 million years ago, may be ancestral to all the other species of this genus, with the exception of A. anamensis, a hominin dating to c.4.1 million years ago, discovered in 1994. A. afarensis is known from fossils found at a number of sites in Ethiopia and at Laetoli, Tanzania. The 3.6-million-year-old footprints, preserved in volcanic ash at Laetoli, are commonly attributed to this species. Postcranial skeletal remains show that A. afarensis was relatively small, standing 3.5 to 5 ft (1 to 1.6 m) tall and weighing 45 to 110 lb (20 to 50 kg).

Remains of an australopithecine of similar size and between 2 to 3 million years old have also been found in S Africa. Known as A. africanus, it had molars slightly larger than A. afarensis, but in other respects it had decidedly more human features than A. afarensis, including a higher forehead, less prominent brow ridges, and a shorter face. Most researchers consider A. africanus to be a distinct species that is descended from A. afarensis.

Two other well-known australopithecines, A. boisei (from E Africa) and A. robustus (from S Africa), featured very large molars and premolars, very thick jaws, and craniums topped by prominent crests. These features probably reflect a relatively specialized diet of rough vegetable matter. In contrast, A. afarensis and A. africanus had cranio-dental features consistent with a more generalized diet. The large-toothed australopithecines also had skeletons indicative of a heavier build than the small-toothed australopithecines; the former are believed to have weighed 25 to 50 lb (10 to 20 kg) more than the latter, even though they were approximately the same height. Based on these pronounced differences, australopithecines are classified into two distinct types: gracile and robust. The robust australopithecines all became extinct between 1.5 and 1 million years ago, while one of the gracile autralophithecines is believed to have given rise to the branch leading to the emergence of the genus Homo c.2.5 million years ago.

The species A. barhelghazali is attributed to a 3.5-million-year-old jaw and tooth remains found in central Chad in 1995. The first remains of an Australopithecus recovered outside of E or S Africa, this surprisng find suggests hominin evolution took place over a much larger portion of Africa than many experts had originally believed. A cranium specimen recovered from W Turkana, Kenya, is attributed to the robust species A. aethiopicus. This fossil is 2.5 million year old and shares certain primitive features with A. afarensis, providing strong evidence that the robust A. aethiopicus descended from the gracile A. afarensis. Many experts believe A. aethiopicus subsequently gave rise to the two major robust species, A. boisei and A. robustus. Tibia and mandible fragments from Allia Bay, Lake Turkana, are attributed to yet another species, A. amarensis, providing evidence for bipedalism c.4.1 million years ago.

There is no consensus among the experts concerning the evolutionary relationship among the various australopithecines, or between the australopithecines and Homo habilis, which is considered by many to be the earliest species of the genus Homo. One proposal is that A. afarensis gave rise to two distinct lineages c.3 million years ago: One branch became the robust australopithecines (doomed to extinction), while the other branch became the gracile species (one species of which eventually evolved into H. habilis). Many researchers believe that the species that evolved into H. habilis was A. africanus. Other experts reject this model, as well as the claim that A. africanus played any such key role. Increasingly, specialists favor assigning the robust australopithecines to a completely seperate genus, Paranthropus, because of the very significant physical differences between the robust and gracile species. According to this view, A. afarensis was the last common ancestor of these two distinct types of hominins.

See also human evolutionhuman evolution,
theory of the origins of the human species, Homo sapiens. Modern understanding of human origins is derived largely from the findings of paleontology, anthropology, and genetics, and involves the process of natural selection (see Darwinism).
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Bibliography

See D. C. Johanson and M. A. Edey, Lucy: The Beginnings of Humankind (1981); E. Delson, ed., Ancestors: The Hard Evidence (1985); R. Leakey and R. Lewin, Origins Reconsidered (1992).

Australopithecus

[ȯ‚strā·lō′pith·ə·kəs]
(paleontology)
A genus of near-men in the subfamily Australopithecinae representing a side branch of human evolution.
References in periodicals archive ?
While that's still one theory, Brown now leans toward the more striking idea that Flores man represents a direct link to the much more ancient australopithecines, a notion that raises all sorts of interesting speculation because australopithecine fossils have never been found outside of Africa.
Ample evidence has shown that australopithecines were walking upright by this time, but the first traces of this skeleton - the four bones of an instep and beginning of the big toe - suggested that this species also was capable of grasping and climbing like a chimpanzee.
Such a comparison can be used to test two competing claims that can be treated as testable hypotheses: (1) the consensus among mainstream scientists that australopithecine anatomy is intermediate between those of apes and humans and (2) the young-earth creationist claim that australopithecines are "just apes," unrelated to humans (Mehlert, 2000; Line, 2005; Murdock, 2006).
Chimpanzee hand morphology cannot sustain the gamut of finessed grips; australopithecine and H.
The australopithecine cobble from Makapansgat, South Africa.
Researchers generally agree that small-brained members of the human evolutionary family, known as australopithecines, evolved into the first representative of the Homo line between 3 million and 2 million years ago.
One cannot, however, exclude the possibility that australopithecines may have had some form of communication, including the use of sounds.
In Johannesburg, I had the privilege of working closely with James Kitching, the vastly experienced palaeontologist working on the Makapansgat Australopithecine deposits.
Despite the overwhelming lack of palaeoanthropological fieldwork outside of Europe and the complete lack of an australopithecine or pithecanthropine grade fossil record within it, he suggested that because `the archaeological evidence of man's antiquity in Europe is more extensive and complete than for any other continent .
This australopithecine may have acquired brucellosis by eating fetal tissue from a similar animal, according to D'Anastasio.
afarensis, in a roughly 2-million-year-old robust australopithecine species known as Australopithecus robustus, and in modern gorillas, the researchers report in an upcoming Proceedings of the National Academy of Sciences.
In southern Africa the first Australopithecine had been named at Taung but sidelined by Sussex's joker at Piltdown.