It has relatively small front teeth, but massive grinding teeth in a large lower jaw. Most specimens have sagittal crests. Its diet would have been mostly coarse, tough food that needed a lot of chewing. The average brain size is about 530 cc. Bones excavated with robustus skeletons indicate that they may have been used as digging tools. Australopithecus boisei (was Zinjanthropus boisei)A. boisei was found at Lake Turkana, Northern Kenya and existed between 2.1 and 1.1 million years ago. It was similar to robustus, but the face and cheek teeth were even more massive, some molars being up to 2 cm across. The brain size is very similar to robustus, about 530 cc. Some consider boisei and robustus to be variants of the same species. Australopithecus aethiopicus, robustus and boisei are known as robust australopithecines, because their skulls are more heavily built. However, in the same sedimentary layer, another cranium was also found belonging to a species of hominid named Homo ergaster. This hominid species is believed to be a different geographical population of Homo erectus Homo habilisH. habilis, "handy man", was so called because of evidence of tools found with its remains by the Leakeys in1961. Habilis existed between 2.4 and 1.5 million years ago. It is very similar to australopithecines in many ways. The face is still primitive, but it projects less than in A. africanus. The back teeth are smaller, but still larger than in modern humans. The average brain size, at 650 cc, is considerably larger than in australopithecines. Brain size varies between 500 and 800 cc, overlapping the australopithecines at the low end and H. erectus at the high end. The brain shape is also more humanlike. The bulge of Broca's area, essential for speech, is visible in one habilis brain cast, and indicates it was possibly capable of rudimentary speech. Habilis is thought to have been about 127 cm (5'0") tall, and about 45 kg (100 lb) in weight, although fe...
