The term australopithecine refers generally to any species in the related genera of Australopithecus and Paranthropus. It may also include members of Kenyanthropus, Ardipithecus, and Praeanthropus. The term comes from a former classification as members of a distinct subfamily, the Australopithecinae. They are now classified by some within the Australopithecina subtribe of the Hominini tribe. Members of Australopithecus are sometimes referred to as the "gracile australopithecines", while Paranthropus are called the "robust australopithecines".
The australopithecines occurred in the Plio-Pleistocene era, and were bipedal and dentally similar to humans, but with a brain size not much larger than that of modern apes, with lesser encephalization than in the genus Homo. Humans (genus Homo) may have descended from australopithecine ancestors, while the genus Ardipithecus is a possible ancestor of the australopithecines.
Phylogeny
Phylogeny of subtribe Australopithecina according to Briggs & Crowther 2008, p. 124.
- Australopithecina
- Australopithecus
- A. afarensis
- A. africanus
- A. anamensis
- A. bahrelghazali
- A. garhi
- Paranthropus
- P. robustus
- P. boisei
- P. aethiopicus
- Ardipithecus
- A. ramidus
- A. kadabba
- Australopithecus
Physical characteristics
The post-cranial remains of australopithecines show they were adapted to bipedal locomotion, but did not walk identical to humans. They have a high brachial index (forearm/upper arm ratio) when compared to other hominids, and they exhibit greater sexual dimorphism than members of Homo or Pan but less so than Gorilla or Pongo. It is thought that they averaged heights of 1.2â€"1.5 metres (3.9â€"4.9 ft) and weighed between 30 and 55 kilograms (66 and 121 lb). The brain size may have been 350 cc to 600 cc. The postcanines (the teeth behind the canines) were relatively large, and had more enamel compared to contemporary apes and humans, while the incisors and canines were relatively small, and there was little difference between the males' and females' canines compared to modern apes.
Relation to Homo
Most scientists maintain one of the australopithecine species evolved into the Homo genus in Africa around two million years ago. However there is no consensus on which species:
"Determining which species of australopithecine (if any) is ancestral to the genus Homo is a question that is a top priority for many paleoanthropologists, but one that will likely elude any conclusive answers for years to come. Nearly every possible species has been suggested as a likely candidate, but none are overwhelmingly convincing. Presently, it appears that A. garhi has the potential to occupy this coveted place in paleoanthropology, but the lack of fossil evidence is a serious problem. Another problem presents itself in the fact that it has been very difficult to assess which hominid represents the first member of the genus Homo. Without knowing this, it is not possible to determine which species of australopithecine may have been ancestral to Homo."
Marc Verhaegen has argued that an australopithecines species could have also been ancestral to the Pan genus (i.e. chimpanzees).
Asian australopithecines?
A minority held viewpoint among palaeoanthropologists is that australopithecines moved outside of Africa. A notable proponent of this theory is Jens Lorenz Franzen, formerly Head of Paleoanthropology at the Research Institute Senckenberg. Franzen argues that robust australopithecines had reached not only Indonesia, as Meganthropus, but also China:
"In this way we arrive at the conclusion that the recognition of australopithecines in Asia would not confuse but could help to clarify the early evolution of hominids on that continent. This concept would explain the scanty remains from Java and China as relic of an Asian offshoot of an early radiation of Australopithecus, which was followed much later by an [African] immigration of Homo erectus, and finally became extinct after a period of coexistence."
In 1957, an Early Pleistocene Chinese fossil tooth of unknown province was described as resembling P. robustus. Three fossilized molars from Jianshi, China (Longgudong Cave) were later identified as belonging to an Australopithecus species (Gao, 1975). However further examination questioned this interpretation; Zhang (1984) argued the Jianshi teeth and unidentified tooth belong to H. erectus. Liu et al. (2010) also dispute the Jianshi-australopithecine link and argue the Jianshi molars fall within the range of Homo erectus:
"No marked difference in dental crown shape is shown between the Jianshi hominin and other Chinese Homo erectus, and there is also no evidence in support of the Jianshi hominin's closeness to Australopithecus."
Wolpoff (1999) though points out that in China "persistent claims of australopithecine or australopithecine-like remains continue".
