A Science Odyssey
People and Discoveries

4.4 million-year-old human ancestor is found

Tim White, Berhane Asfaw, and Gen Suwa, who have long worked together unearthing and analyzing fossils in Africa, made a new and remarkable discovery in 1993. In Ethiopia, they found hominid skull, jaw, and arm bones plus a few teeth that dated back to 4.4 million years ago. That would make these the oldest hominid ancestors yet identified, and the most primitive hominid species known.

Announcing these fossils in 1994, the group named them Australopithecus ramidus, putting them in the same genus as the 1.75-million-year-old Australopithecus boisei and the 3-million-year-old "Lucy." But eight months later, the researchers changed the name to Ardipithecus ramidus, moving the species represented by the fossils into a different genus. They did not fully explain the change, but were continuing to analyze the fossils and planned publication of their findings within a few years. (According to naming convention, discoverers have the right to name the species, but acceptance of the genus they suggest depends upon the agreement of other workers in the field.)

The species looked to be a link between ancient African apes and Australopithecus.It shared physical features of both groups. Paleontologists Meave Leakey and Alan Walker write that "Ardipithecus, with its numerous chimplike features, appears to have taken the human fossil record back close to the time of the chimp-human split."

Discussion continues over whether Ardipithecus is a hominid or not, whether it walked on two feet or not, and what its relationship is to the 3.94.2 million year old fossils found in 1995 by Meave Leakey and Alan Walker in Kenya (Australepithecus anamensis). These latter show clear signs of walking upright and of living in a wooded area, throwing into doubt the usual explanation of bipedalism as an adaptation to living in the savannah. These recent discoveries provide important evidence in the search for human origins, but points out Walker, "As with so many scientific discoveries, this one also provokes more fascinating questions."

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