New Ethiopian Fossils May Represent Oldest Human Ancestor Yet

Researchers working in Ethiopia have unearthed the remains of a creature thought to occupy a spot on the family tree quite close the evolutionary branching point between humans and chimpanzees. According to a report published today in the journal Nature, these remains belong to a new subspecies of the hominid genus Ardipithecus, previously known fossils of which date to 4.4 million years ago. The new fossils, however, come from sediments dated to between 5.2 and 5.8 million years ago, and thus may represent the earliest known human ancestor.

Yohannes Haile-Selassie, a doctoral candidate at the University of California at Berkeley, discovered the fossils in Ethiopia's Middle Awash study area, a locale famous for yielding other key fossils, such as the 4.4 million-year-old Ardipithecus ramidus and the 2.5 million-year-old Australopithecus garhi. Subsequent analyses of the fragmentary remains—which include a jawbone with teeth; hand, foot and arm bones; and a piece of collar bone—revealed a bipedal creature with teeth similar to those of later hominids. These teeth and certain skeletal features are more primitive than those belonging to Ardipithecus ramidus, however, thus leading Haile-Selassie to designate the fossils as a new subspecies, Ardipithecus ramidus kadabba.

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A.r.kadabba is not without competition for the distinction of being the earliest human ancestor. Earlier this year a French team unveiled the 6 million-year-old remains of Orrorin tugenensis, a new species that the discoverers regard as hominid. (These researchers consider Ardipithecus a chimpanzee ancestor.) For his part, Haile-Selassie asserts that more information is required to resolve Orrorin's place in the family tree. And with excavations resuming in the Middle Awash this fall, more clues to our elusive evolutionary past may yet come from Ardipithecus. --Kate Wong

A New Human Ancestor?

Image: FRED SPOOR; copyright National Museums of Kenya
Researchers working in Kenya have unearthed fossils that could upset a long-held view of human origins. According to a report published today in the journal Nature, the remains represent a previously unknown hominid genus and species from which modern humans may have descended. For decades that distinction belonged to Australopithecus afarensis—a species typified by the famous 3.2-million-year-old Lucy skeleton. But the new discovery, dubbed Kenyanthropus platyops, comes from roughly the same time interval and thus renders Lucy's ancestral status far less certain.

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Meave Leakey of the National Museums of Kenya and her colleagues recovered the Kenyanthropus remains—which include jaws, teeth and a skull dated to between 3.2 and 3.5 million years old—from mudstone sediments in northern Kenya’s Turkana basin. (The skull is apparently the oldest almost complete early human cranium known.) Subsequent analysis revealed a creature rather different from Lucy and her kin. In particular, Kenyanthropus has a far flatter face and smaller molar teeth—feeding-related differences that suggest the two groups could have coexisted without competing for food resources.

"Now that we have a new form of early hominid from the same time period that is quite distinct from afarensis, the anthropologists will have to decide which of these forms of early human actually lies in our ancestral tree," University of Utah geologist Frank Brown, who dated the fossil, remarks. "It cannot be both." --Kate Wong


ما فهمته يا اخى عبد المسيح هو ان الجمجمة المكتشفة هى عائلة جديدة new family تقع فى تطورها بين الانسان والشيمبانزى ولكن هى لكائن اقل تطوراً من الانسان الحالى بكثير .

اذا فهمت شئ آخر من المقال من فضلك اشرحه لى .

وقل لى بالله عليك ... هل هذه جمجمة انسان ؟ باين عليه كان انسان اهبل .