ago, and the genus flourished until it seemed to have become extinct about 1.5 million years ago. All the australopithecines were efficiently bipedal and thus indisputable hominines. In details of their teeth, jaws, and brain size, however, they differ enough among themselves to warrant division into four species: A. afarensis, A. africanus, A. robustus, and A. boisei. The earliest australopithecine is A. afarensis, which lived in eastern Africa between 3 and 3.9 million years ago. Found in the Afar region of what is now Ethiopia and in Tanzania, A. afarensis had a brain size a little larger than those of chimpanzees. Some of the species possessed canine teeth somewhat more projecting than those of later hominines. No tools of any kind have been found with A. afarensis fossils. Between about 2.5 and 3 million years ago, A. afarensis apparently evolved into a later australopithecine, A. africanus. Known primarily from sites in southern Africa, A. africanus possessed a brain similar to that of its predecessor. However, although the size of the chewing teeth remained large, the canines, instead of projecting, grew only to the level of the other teeth. As with A. afarensis, no stone tools have been found in association with A. africanus fossils. By about 2.6 million years ago, the fossil evidence reveals the presence of at least two, and perhaps as many as four, separate species of hominines. An evolutionary split seems to have occurred in the hominine line, with one group evolving toward the genus Homo, and finally to modern humans, and the others developing into australopithecine species that eventually became extinct. The australopithecine species that eventually became extinct includes the robust australopithecines, A. robustus, that lived in southern Africa, and A. boisei, found only in eastern Africa. Snell 4The robust australopithecines represent an unusual adaptation because their principal difference from other australopithecines l...
