The earliest fossils of the group Hominidae are the australopithecines. These hominids have been found mostly in a few locations in South Africa and Eastern Africa. The first australopithecine fossil discovery was of an Australopithecus africanus skull found in South Africa in 1925 by Raymond Dart.
Dated at 4.4 Million years old, early Pliocene, the earliest
known specimens are fragments of skeletons found in Ethiopia and Kenya
and are called Ardipithecus ramidus and a later form called Australopithecus
anamensis. Australopithecus anamensis is dated between
4.2 and 3.9 million years old. The australopithecines were relatively small-brained
hominids. They walked upright on two legs. There are believed
to be seven species within this genus. Only Australopithecus africanus
and Australopithecus africanus are thought to have contributed
to the hominid lineage; the others are viewed as evolutionary dead-ends.
It is also believed that it is from the species Australopithecus afarensis
that later gave rise to our genus, Homo, roughly 2.5 million years ago.
This is under debate, however, since it is the species Australopithecus
africanus which more closely resembles our genus in certain characteristics.
africanus comes from southern Africa. This species more
closely resembles humans from the neck up, but it is more ape-like than
A. afarensis from the neck down. Australopithecus
africanus has a larger cranial capacity than does Australopithecus
afarensis, but it has longer arms and shorter legs.