By Eugene M. McCarthy, Ph.D.
This extremely ancient hominid was discovered in 1992 by a team led by anthropologist Tim White of the University of California, Berkeley.
The material was initially assigned to Australopithecus by White et al. (1994). But they later claimed (White et al. 1995) the creature they had found was different from australopithecines — different enough to deserve a new genus, Ardipithecus, of its own.
The first fossils recovered were pieces of the skull, a mandible, teeth, and arm bones. Additional fragments recovered in 1994, together with the previous finds, added up to about 45 percent of the skeleton. This was the now famous "Ardi", a 50-kilogram (110 pound) female. Ultimately, the material recovered included most of the cranium, as well as the hands, feet, and pelvis. Ardi was recovered from Pliocene strata at a site named Aramis, near the Middle Awash River, in the Afar Depression, Ethiopia (see maps at right).
Later, between 1999 and 2003, a team headed by Sileshi Semaw, of Indiana University, discovered fragmentary remains from nine separate Ardipithecus ramidus individuals at As Duma in the Kada Gona river valley on the western margin of the Afar.
All specimens presently assigned to Ardipithecus ramidus date to around 4.4 mya and show a mixture of ape-like and australopithecine-like features. Because A. ramidus shares certain characteristics with apes, some experts think it's an ancestor of chimpanzees instead of humans. A growing consensus, however, seems to consider it close to a common ancestor of both apes and humans since its teeth are intermediate between those of earlier apes and Australopithecus afarensis.
The brain size of this hominid was on the small side, even for an ape. The cranial capacity was between 300 and 350 cc — smaller than that of the typical chimpanzee, and considerably smaller than that of a gorilla. It was smaller, too, than the usual australopithecine's — less than a quarter the size of a modern human's.
According to an analysis of the postcranial material presented in a recent package of articles published in the journal Science, Ardipithecus ramidus was bipedal when on the ground, but went on all fours when climbing trees, as is, of course, the case with modern humans. However, unlike modern humans this hominid had a big toe that could grasp branches.
Wear patterns on dental remains indicate Ardipithecus ramidus was omnivorous, and ate a broad range of foods, but that it did not eat many items that were fibrous, hard, or abrasive (Teaford and Ungar 2000). However, since stone tools (and fire) were still far in the future, meat could not have been consumed with any regularity. The oldest known stone tools date to about 2.5 mya (Semaw et al. 1997, Semaw 2000) — nearly two million years later than all known fossils of A. ramidus.
Habitat: Woodland.
Diet: Omnivorous.
Synonym: Australopithecus ramidus.
Etymology: The name of this hominid is constructed from the Greek suffix -pithecus and two words from the Afar language, ardi meaning "ground" or "floor", and ramid meaning "root", plus the Latin masculine ending -us. This etymology indicates that White et al. intended from the outset (White et al. 1995), when they named this creature, to convey that it is on the "ground floor" — or at the very root — of hominid evolution. Whether this is actually the case remains to be shown.
Interesting facts and information about other ancient hominids:
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