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. There is considerable disagreement, however, among experts on the number of species that should be included within the genus. Some of the species are considered by some experts to belong to other genera, and some remains classified among the above species by some experts are considered by other experts to belong to additional Australopithecus species. Two of the seven species listed above—A. bahrelghazali and A. anamensis—are based on very fragmentary remains. Among the many anatomical traits shared by these species 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 that have been reported found include A. garhi in Ethiopia in 1999, A. prometheus in 1948 and the 1990s in South Africa, and A. sediba in 2008–9 in South Africa.

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 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 ?
A point-by-point comparison of ape, australopithecine, and human anatomy presents another opportunity that should be seized.
If we ignore our inherited flexibility, we may end up like the robust australopithecines sooner than we think.
The brain capacity is small, with some specimens fitting within the range of variation of later forms of australopithecines, about 30 [in.sup.3] (500 [cm.sup.3]) and others with lower values, lower than 24 [in.sup.3] (400 [cm.sup.3]).
The volume of australopithecine brains, determined by endocasts, is about 30% larger than that expected based on a simple regression against body weight for extant apes.
Her australopithecine relatives seem to have ranged between 3 and 4 feet in height and to have weighted perhaps 65 pounds.
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.
Researchers had hoped that the australopithecine fossil would shed light on the transition to an upright stance and tool use between 4, million and 3 million years ago.
But when she worked in Anthropology, I was a Cal student myself, showing up at her office strategically so she would take me to lunch, learning along with her about California Indians, Inuit art, and Australopithecines. Dad's Anne-mediated connections with Robert Heizer and Theodora Kroeber led to the Sierra Club's Almost Ancestors, a lament for California's lost native peoples and their special knowledge of place.
And for over a million years, our ancestors lived alongside a rather enigmatic group, the robust australopithecines. Their origins remain uncertain even 70 years after their discovery.
The Dikika baby lived about 3.3 million years ago, even before "Lucy," that most famous of all australopithecines. When the Dikika baby and her family looked to the night sky and the constellation Cepheus, which would come to bear the name of the king who would one day rule their land (at least in tales), what is now Trumpler 37 was a vast nebula that probably rivaled Orion.
Australopithecus boisei sported a gorilla like bony crest and was the most robustus among all the Australopithecines, which thrived for almost a million years only to come to an evolutionary dead end.