Many Hominid Species

figure 43-20

Many different species of hominids may have coexisted in time and possibly interacted during the past 7 million years. Scientists continue to find new hominid fossils and debate the exact classification of some fossils. This diagram represents one interpretation of the fossil record.

Paleontologists continue to find new hominid fossils. Although the exact classification of some fossils is strongly debated, it is clear that human evolution did not proceed as a single lineage of increasingly humanlike forms. Rather, several hominid forms arose, thrived, and became extinct over the past 7 million years, as shown in Figure 43-20. Furthermore, different species of hominids may have coexisted in time and possibly interacted.

In 1995, Mary Leakey and colleagues at the National Museums of Kenya announced the finding of a new hominid species, Australopithecus anamensis, that predated A. afarensis (Lucy's species) by about 300,000 years. Like Lucy's species, this species was also similar to a chimpanzee but probably bipedal. A possible descendant of Lucy's species was A. africanus, which lived about 2.3 to 3 million years ago. It was taller and heavier than Lucy's species and had a slightly larger brain capacity (430 to 550 cm3).

Three more-recent species, A. aethiopicus, A. robustus, and A. boisei, date from about 2.6 million to 1 million years ago. The physical characteristics of these later species suggest that they were a different lineage from A. afarensis. For example, they had heavier skulls, larger molars, and generally thicker bodies than Lucy's species did. Their brain capacity ranged from 450 to 600 cm3. Some scientists call these later hominids robust australopithecines, and some scientists place them in the genus Paranthropus instead of in the genus Australopithecus.

Hominids in the Fossil Record naiiest hominidlj-

These species are the earliest known primates whose traits are more humanlike than apelike. These ' traits include the ability to walk upright and smaller teeth, flatter faces, and larger brains than earlier primates had. Fossils of these species have been found in Africa.

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