domingo, 18 de noviembre de 2007

Mama, Is That You? Possible Ape Ancestor Found

Jennifer Viegas, Discovery News

Nov. 12, 2007 -- A toothy, nut-chomping large ape from Kenya may represent a new species that was, or was very close to being, the last common ancestor to gorillas, chimpanzees and humans, according to a new study that outlines the recently discovered, 10 million-year-old species.

Called Nakalipithecus nakayamai, the ape lived within a critical window of evolutionary time.

Lead author Yutaka Kunimatsu explained to Discovery News that molecular studies of living apes indicate gorillas, chimps and humans diverged from each other in Africa during the Late Miocene 11-5 million years ago.

"Nakalipithecus is derived from Africa and from an appropriate age," Kunimatsu, a Kyoto University primate researcher, said.

Fossil remains of the species, excavated by the researchers in the Samburu Hills of northern Kenya, include a jawbone and 11 telltale teeth.

"Based on the dentition, (the ape) was approximately the size of female gorillas to orangutans and it had thick enamel and low, voluminous cusps on its cheek teeth," Kunimatsu explained, "so it is likely that this ape ate a considerable amount of hard objects, possibly nuts or seeds."

Other studies suggest the landscape of northern Kenya at the time would have consisted of woodlands with some open patches.

The findings were published today in the Proceedings of the National Academy of Sciences.

An odd twist to the find is that the new ape most closely resembles another related species, Ouranopithecus macedoniensis , from Greece. Some researchers had even thought the Greek ape was the last common ancestor, or at least close to it.

The Africa/Greece connection likely was due to apes on the move, according to Kunimatsu. He said the oldest known ape fossil dates to 25 million years ago and was found in northern Kenya.

"It is 16-17 million years ago that apes started to appear in the fossil record in Europe, and 13 million years ago in Asia," he said. "It is therefore natural to think that the ancestor of all apes originated in Africa and then, during the course of evolution, some apes went out of Africa and dispersed into Europe and Asia."

Martin Pickford, a paleontologist at the National Museum of Natural History in Paris, believes the latest finds are extremely significant.

"I can't overstress the importance of these fossils from the Late Miocene of Kenya," Pickford told Discovery News. "They are just what the doctor ordered for those of us interested in the divergence between the African apes and humans."

He explained that some researchers previously theorized that the ancestor to African apes and primates may have originated in Eurasia, since so many early ape fossils come from Asia and southern Europe-primarily Greece, Turkey and Bulgaria. The hypothesis was "an offspring of the previous dearth of African fossils from the Late Miocene," he said.

Pickford added, "But now, this tremendous black hole is being filled, and by fossils which show clear affinities with extant African apes and humans."

While scientists continue to debate which ape may have been the actual "mother" of all living great apes, including humans, Africa now appears to have been its homeland, with related lineages that sprung up in Ethiopia, Greece and Turkey.

The entire matter, Pickford said, is "very intriguing and food for thought...indeed, a feast for thought."

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