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Related to Australopithecus: Australopithecus africanus


(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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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).


A genus of near-men in the subfamily Australopithecinae representing a side branch of human evolution.
References in periodicals archive ?
sediba--represented in the new studies by fossils from a young male and an adult female--possessed traits typical of both Australopithecus and Homo species, Berger's team contends.
De Ruiter suspects that an isolated population of the hominid species Australopithecus africanus gradually evolved into A.
The face is tall with a massive brow ridge, yet the mid-face is short (in superoinferior dimension) and less prognathic than in (chimpanzee) or Australopithecus,'' one of the article said.
These specimens sample the right time to look into the relationship between Australopithecus anamensis and Australopithecus afarensis and will play a major role in testing the ancestor-descendant hypothesis.
A date younger than 2 million years would support the idea that many Homo species, as well as many Australopithecus species (SN: 8/10/13, p.
However, the new analysis suggested that these traits did not arise as a single package but several key ingredients once thought to define Homo evolved in earlier Australopithecus ancestors between 3 and 4 million years ago, while others emerged significantly later.
TEHRAN (FNA)- After 13 years of meticulous excavation of the nearly complete skeleton of the Australopithecus fossil named Little Foot, South African and French scientists have now convincingly shown that it is probably around 3 million years old.
3 million years ago and without skeletal evidence, anthropologists believed it was similar to the ancient species Australopithecus and had evolved from this genus.
COLLEGE STATION, Texas, April 11, 2013 /PRNewswire-USNewswire/ -- Close examination of the lower jawbone, teeth and skeleton of the hominid species Australopithecus sediba proves conclusively that it is uniquely different from a closely related species, Australopithecus africanus, according to a series of papers authored by a scientific team that includes several Texas A&M University researchers.
The bones don't belong to the Lucy fossil's species, Australopithecus afarensis -- the only hominid (or member of the human lineage) thought to be living then, according to findings reported in the journal Nature.
The species - dubbed Australopithecus Sediba - had ape arms but human-like hands, which could have been used to make tools and climb trees, a small but humanshaped brain and a pelvis which allowed it walk in an upright fashion.
Australopithecus afarensis was long thought to have lived on vegetation alone; the discovery sheds light on early dietary habits and tool use.