Australopithecus Our Distant Ancestor
One of our hominid ancestors is probably Australopithecus (from the Latin word austral, meaning "southern," and the Greek word pithekos, meaning "ape") or a primate very much like it. Figure 1-11 shows reconstructions of the animal's face and body. The name Australopithecus was coined by an Australian, Raymond Dart, for the skull of a child that he found in a box of fossilized remains from a limestone quarry near Taung, South Africa, in 1924. (The choice of a name to represent his native land is probably not accidental.) We now know that many species of Australopithecus existed, some at the same time.
The skull of the "Taung child" did not belong to the earliest species, which lived more than 4 million years ago. These early hominids were among the first primates to show a distinctly human characteristic: they walked upright. Scientists have deduced their upright posture from the shape of their back, pelvic, knee, and foot bones and from a set of fossilized footprints that a family of australopiths left behind, walking through freshly fallen volcanic ash some 3.6 million to 3.8 million years ago. The footprints feature the impressions of a well-developed arch and an unrotated big toe more like that of humans than of apes. The evolutionary lineage from Australopithecus to humans Homo sapiens "Lucy" is not known precisely, in part because many Australopithecus
W H AT ARE T H E O RIGIN S O F BRA IN A ND BE H AVIO R? ■ 21
A. robustus
A. afarensis
A. africanus
] Common ancestor
H. habilis I I H. erectus I
H. neanderthalensis | H. sapiens |
1600 1400
I 1000 Ii 800
H. neanderthalensis
H. erectus
H. habilis
Common A. africanus ancestor
Millions of years ago
H. habilis
Common A. africanus ancestor
Figure 1-12
H. sapiens species evolved, some contemporaneously. One possible lineage is shown on the left in Figure 1-12. A common ancestor gave rise to the Australopithecus lineage, and one member of this group gave rise to the Homo lineage.
The last of the australopith species disappears from the fossil record about 1 million years ago after coexisting with other hominids for some time. Also illustrated in Figure 1 -12, at the right, is the large increase in brain size that evolved in the hominid lineage. The brain of Australopithicus was about the same size of that of nonhuman apes, but succeeding members of the human lineage display a steady increase in brain size.
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