A publication of the Archaeological Institute of America
Debate over whose fossils represent our earliest ancestor continues, the newest contender being the 5.2-5.8-million-year-old fossils--a right mandible, four teeth, two arm and finger bones, one collar bone, and a toe bone--found between 1997 and 2001 in the Middle Awash region of Ethiopia. Just reported in the journal Nature by paleontologist Yohannes Haile-Selassie of the University of California at Berkeley, the bones have been dubbed Ardipithecus ramidus kadabba, a subspecies of A. ramidus, already known from 4.4-million-year-old fossils.
In the Afar language, kadabba means progenitor. The name was chosen because the fossils are close in time to the divergence of the ape-chimp and human lines, estimated on genetic evidence to have happened 6.5 to 5.5 million years ago. It also reflects Haile-Selassie's belief that his finds, and not the six-million-year-old Orrorin tugenensis discovered recently in Kenya, are on the human line (see "Ancient Ancestors," July/August 2001). Haile-Selassie claims that his Ardipithecus postdates the split but is close to the last common ape-chimp and human ancestor. O. tugenensis, he contends, could be the last common ancestor, an ape and chimp ancestor, or the ancestor of a dead-end evolutionary line.