Australopithecine

The term **Australopithecine** ('australos' for short) refers to any species in the genus _Australopithecus_ or the genus _Paranthropus_. These were bipedal hominids that lived in the Pliocene–Pleistocene epochs.

## Description

Australopithecines had ape-like and human-like qualities. They were mainly bipedal, like humans, but could probably climb and live at least partly in trees. Their arms were longer in proportion to their bodies, which is useful when moving above the ground. The efficiency of their walking is difficult to estimate, but they were not so well adapted to bipedalism as humans.

The males were much larger than the females, which suggests a family arrangement with a dominant male and several females, as with modern apes. Nothing is known for certain about their use of tools.

The australopithecines had a brain size not much larger than modern apes. The great increase in brain size of modern man began with the genus _Homo_: it did not start with the australos.

The arrangement of their teeth, especially the dental arcade, was similar to humans. They did not have the large canine teeth characteristic of present-day apes.

## Classification

Australopithecines are in the hominin tribe of African apes that includes humans and all ancestors of _Homo sapiens_ back to our split from the apes.

The australopithecines appeared in the late Miocene epoch:

- _Australopithecus_, about four million years ago (mya)
- _Paranthropus_, about 2.7 mya

When used alone, the term refers to both genera together. _Australopithecus_ is sometimes referred to as the "gracile (slender) australopithecines", while _Paranthropus_ are also called the "robust australopithecines".

### Other genera

- _Kenyanthropus_ (3.5 to 3.2) mya is either a separate genus of australos, or a species of _Australopithecus_.
- _Ardipithecus_ (5.6 and 4.4) mya is a Miocene hominin. It had a grasping big toe, and therefore could live in trees as well as on the ground. The term "facultative biped" is used.
- _Sahelanthropus_, also a Miocene hominin, lived about seven million years ago (mya). The relationships of this species to the australos is unclear.
- _Orrorin_, at 6.1 to 5.7 mya is known from 20 pieces of bone, and its relationships are unclear. _Orrorin_ is both earlier, by almost 3 million years, and more similar to modern humans than is _A. afarensis_. The main similarity is that the Orrorin femur is morphologically closer to that of _H. sapiens_ than is _Lucy's_; there is, however, some debate over this point.

## Ancestry

A likely ancestor of the australopithecines is the _Ardipithecus_ genus, which lived in East Africa. The genus _Homo_ (humans) appears about 2.4 million years ago with _Homo habilis_.

Australos moved into mixed savannah/woodland habitats as the climate cooled in the later Miocene. This explains their adaptations to walking or walking plus climbing. It also explains the changes to their diet and teeth, though not in detail.

## List

The australopithecines according to Briggs & Crowther are:
- Australopithecina
    - _Australopithecus_
        - _A. afarensis_
        - _A. africanus_
        - _A. anamensis_
        - _A. bahrelghazali_
        - _A. garhi_
    - _Paranthropus_
        - _P. robustus_
        - _P. boisei_
        - _P. aethiopicus_
    - _Ardipithecus_
        - _A. ramidus_
    - _Orrorin_
        - _Orrorin tugenensis_
    - _Sahelanthropus_
        - _Sahelanthropus tchadensis_