The Earliest Hominines Essay Research Paper The

The Earliest Hominines Essay, Research Paper The Earliest Hominines The first undoubted hominine discovered thus far is Ardipithecus ramidus, which was found in 1994 and is known from 17 fragments of teeth and bone. It dates to approximately 4.4 million years ago. Thought to be the descendent genus of Ardipithecus is the genus Australopithecus; individuals of this genus were bipeds while on the ground and had ape-like brains and dexterous hands. There are at least six species of Australopithecus: A. anamensis, A. afarensis, A. aethiopicus, A. africanus, A. boisei, and A. robustus. In 1924 an unusual fossil was brought to Raymond Dart, an anatomist at the University of Witwatersrand in Johannesburg. This fossil had a curious mix of ape-like and human-like traits. Dart named

the fossil Australopithecus africanus and claimed that, based on the forward position of the foramen magnum, the creature was a biped. At least four species are recognized: A. afarensis and A. africanus being smaller and lacking the massive jaws of the two larger species, A. boisei and A. robustus. A. afarensis and A. boisei are from East Africa, while A. africanus and A. robustus are from South Africa. An earlier species, A. anamensis comes from Kenya, while a single representative of a sixth species, A. aethiopicus comes from West Turkana and is known as the “black skull” for its distinctive black staining. Australopithecus africanus has been discovered at three South African sites: Taung, Makapansgat, and Sterkfontein. All of these sites range in date from 3 to 2.3 mya;

however, a partial foot may be as old as 3.5 million years. Australopithecus afarensis dates to between 3.9 and 2.9 mya, and was discovered in the 1970s and 1990s in the Afar region of northern Ethiopia. Included in this species are the two famous finds of Don Johanson: the remarkably complete female skeleton AL 288-1, known as “Lucy”, and the collection of 13 individuals at Afar Locality 333 which has come to be known as the “First Family”. Material nearly 4 million years old from Laetoli in Tanzania has also been ascribed to A. afarensis, despite suggestions that the wide variation in size of individuals may mean the presence of 2 species. It is likely, however, that A. afarensis size differences represent sexual dimorphism similar to Miocene apes and intermediate

between the greatly dimorphic modern gorillas and the less dimorphic chimpanzees. Other East African sites have yielded fossils similar to A. afarensis or A. africanus. These sites are all 2 million or more years old. The individuals ranged between 3.5 and 5 feet, with weights of between 29 and 45 kg. Australopithecus afarensis and A. africanus are considered to be “gracile” or smaller australopithecines. These two species possessed small incisors, short canines in line with the other teeth, and a rounded dental arch. No gap between the canines and incisors in the upper jaw (diastema), as seen in apes, was present. The molars and premolars were larger than those of modern humans, but were similar in form. Tooth wear indicates that these species chewed as humans do, but with 2

to 4 times the force. The diet was largely tough, fibrous vegetation. A. afarensis individuals tend to show more sivapithecine features, such as a less-rounded dental arch, less shearing tooth wear, slight diastema, and some canine projection, than the later A. africanus individuals. These sivapithecine features suggest a Miocene sivapithecine-like ancestor. Some sex differences have been noticed in these two australopithecines: males seem to develop a bicuspid first lower premolar while females do not; and females seem to possess skeletal features better suited to tree-climbing than males. These differences suggest that males and females may have had slightly different foraging strategies, with males spending more time on the ground and females exploiting trees. Cranial capacity