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Entrances and Exits Between 4 million and 2 million years ago, at least 11 different hominid species existed in central, eastern, and southern Africa. These species fall into three genera: Australopithecus, Paranthropus, and Kenyanthropus. At any given time during this era, from four to seven different species existed simultaneously.8 Paleoanthropologists surmise that at least six of the hominids were Australopithecus. Like earlier hominids, australopithecines can be thought of as bipedal apes, distinct from chimpanzees.9 The brain size of australopithecines (380 to 450 cm3) was slightly larger than that of chimpanzees (300 to 400 cm3). Though the cranium, facial features, and dental anatomy were apelike, they were distinct from the corresponding chimpanzee features. The australopithecines stood about four feet tall and matured rapidly, like the great apes. Skull, pelvis, and lower limbs all display features that indicate these hominids walked erect. Still, the bipedalism, called facultative, was distinct from the obligatory bipedalism employed by Homo hominids. Some paleoanthropologists think the australopithecines could also climb and move effectively through trees. This idea is based on their relatively long upper arms, short lower limbs, and funnel-shaped torsos. Work published in 2000 indicates that some australopithecines might have knuckle-walked like the great apes.10 The earliest australopithecines lived either in a woodland environment or in a mixed habitat of trees and open savannas. Later australopithecines lived only on the grassy plains. Their capacity to climb and move through trees, as well as walk erect, gave these hominids easy mobility in their varied environment. The oldest member of Australopithecus, Australopithecus anamensis, existed between 4.2 and 3.8 million years ago, based on fossils recovered near Lake Turkana in Kenya. Australopithecus afarensis fossils have been recovered in eastern Africa and date to between 4 and 3 million years old. “Lucy” (discovered in the early 1970s by Donald Johanson) is one of the best-known specimens. She is nearly 40 percent complete, with much of the postcranial skeleton intact.11 Remains of Australopithecus bahrelghazali, dated at 3.2 million years ago, have been recovered in Chad. Some paleoanthropologists think, however, that A. bahrelghazali is properly classified as an A. afarensis. Australopithecus africanus lived in South Africa between 3.0 and 2.2 million years ago, based on the fossil record. One of the best-known A. africanus specimens is the “Taung child” discovered in 1924 by Dart. The Taung child was the first australopithecine found.12
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