Hominid Species Time Line
Page 12
II. The More Recent Australopithecine/Paranthropus Species
In the 1930's and 40's, the first specimens of robust australopithecines, as they were originally called, were discovered in east and southern Africa. These discoveries and the ones that followed have considerably complicated our view of the hominid family tree. These cousins of ours are now classified into several distinct species and, interchangeably, into two genera. But whether called australopithecines or paranthropoi, they represent a line—or several lines—of hominids that evolved “along side” early human species and undoubtedly interacted with them. They are not regarded, however, as being in the ancestral line to modern humans.
There is currently no consensus on how to classify these species; the terms Australopithecus and Paranthropus (“beside man”) are used almost interchangeably. It is widely assumed that these species are descendents of either Australopithecus africanus or A. afarensis (or both), and that they remained adapted to a woodland environment. Their obvious specialization as plant-eaters, with massive molars and pre-molars, modified cheek bones, and sagital crests on their skulls, is the basis for their being placed in a new and separate genus by some scientists.
These species are small brained (400-550 cc) compared to human species contemporaneous with them. Their huge teeth and skulls, often topped with prominent dorsal (sagittal) crests to which large jaw muscles attached, show that they specialized in eating tough plant material. Aside from their skulls and teeth, their skeletal remains are not much different from A. africanus. They were larger than chimps, with males standing slightly over five feet tall. The two skulls at left show dramatically the effects of this “chewing” specialization. Our ancestors, in contrast, evolved as omnivores with a taste for meat.
The total number of these later australopithecine species is disputed. Of the four species represented below, the most ancient, A. afarensis, at left, is sometimes regarded as ancestral to both humans and the other australopithecines. Not everyone agrees. The three more recent australopithecines ["Southern Apes"] to the right of A. afarensis were erect-walking, members of the hominid family and contemporaries of the earliest human species.
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A. Afarensis |
A. Africanus |
A. Robustus |
A. Boisei |
