Kenyan Fossils Point to New Species of Human Ancestor
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Fossils discovered in East Africa represent a new species of human ancestor that lived about four million years ago, according to findings published in the August 17 issue of Nature magazine. The discovery sheds new light on the question of when and where upright posture first evolved.
"These fossils place the emergence of bipedalism further back in time by a half million years," said NSF-supported paleoanthropologist Alan Walker of Pennsylvania State University, a member of the research team. "This gets close to the hypothesized time of splitting of the ape and human lineages, and fills in a bit more of the gap in our knowledge of human evolution."
The search for the earliest hominid--the animals on the human family tree--took place in two locations in Kenya's Turkana Basin area. Scientists knew that hominids and African apes share a common ancestor, but lacked the clues to indicate whether that ancestor was quadrupedal or bipedal. In search of this clue, Walker led a research team at Allia Bay while paleontologist Meave Leakey, with funding by the National Geographic Society, investigated a site called Kanapoi.
Fossils discovered at the Kanapoi site--including jaws, teeth and a lower leg bone--were dated at between 3.9 and 4.2 million years old, and showed clearly that their owner walked upright. Leakey and Walker placed the fossils in a new species named Australopithecus anamensis (A. anamensis).
Other research efforts have turned up clues to the emergence of uprightness. In 1994, paleoanthropologist Tim White of the University of California, Berkeley--also supported by the National Science Foundation--announced the discovery in Ethiopia of even older fossils which he identified as Ardipithecus ramidus (A. ramidus), a new genus and species of hominid.
The researchers in Kenya theorize that the Ethiopian fossils discovered by White belong to a sister species to all later hominids, and represent a different branch of the hominid tree. They further theorize that the Kenyan fossils represent the surviving branch--the actual forerunner to our species, Homo sapiens.
The discoveries at Turkana Basin help to paint a picture of the being that bridges the split between apes and humans but leave unanswered questions, pointed out Walker. "What is the relationship of bipedalism to this split? Did bipedalism cause the split? As with so many scientific discoveries, this one also provokes more fascinating questions," he said.
The Kenya findings are also discussed in an article by Leakey, to be published in the September issue of National Geographic magazine. Other members of the Kenyan research team were Craig Feibel of Rutgers University and Ian McDougall of Australian National University.
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