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Missing Link Fossil 'extends Human Family Tree'


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Missing link fossil 'extends human family tree'


By Roger Highfield, Science Editor

Last Updated: 6:01pm BST 22/08/2007



The family tree of humans and great apes stretches back millions of years further than thought, according to scientists who have found the teeth of a "missing link" fossil.


eaapes122.jpgThe teeth from a new species of fossil ape (above) and the team at work in Afar The remains of the new species of great ape have been uncovered in the desert scrubland of Afar about 100 miles east of Addis Ababa, Ethiopia, and represent a hitherto unseen link in the human fossil record which only goes back about six million years and reveals little of how the human line actually emerged from apes.


Dating from around 10 million years ago, the long-sought-after discoveries provide hard evidence of our origins, helping to pin down the date when gorillas split from chimp-human stock revealing this crucial fork in our family tree occurred at least two million years earlier than previously thought.


Timing the divergence between the gorilla, chimp and human lineages has until now been done by studying differences in DNA, and calibrating these splits with only fragmentary fossil evidence.


In the new issue of Nature, Gen Suwa of Tokyo University Museum, Berhane Asfaw of the Rift Valley Research Service and Yonas Beyene of the Ethiopian Ministry of Culture and Tourism, present nine fossil teeth from Ethiopia's Chorora Formation.


The molars "share key similarities" with those of a modern gorilla, Dr Suwa told The Daily Telegraph.


The teeth are those of a new species of fossil ape, dubbed Chororapithecus abyssinicus, and if they come from a creature on the gorilla lineage, as the researchers suggest, then the divergence between gorillas and the chimp-human stock must have happened between 10 million and 11 million years ago, not eight million years ago as had been previously thought.


This would be the earliest recognised primate that was directly related to the living African great apes (gorillas, chimpanzees and bonobos).


Dr Asfaw described the moment of the discovery: "It was our last day of field survey in February 2006, our sharp-eyed field assistant, Kampiro, found the first ape tooth, a canine. He picked it up and showed it to me, and I knew this was something new - Ethiopia's first fossil great ape."


Until recently, ape fossils from 12 to seven million years ago in Africa were extremely limited, leading some scientists to speculate that the direct line of ancestral ape from which gorillas, chimpanzees, and humans emerged, was not African, but rather came back to Africa from Eurasia. But the new find suggests once again, that Africa was the place of origin of both humans and modern African apes.


A leading figure in the field, Prof Tim White of the University of California, Berkeley, commented yesterday: "At last, these investigators have begun illuminate the darkness of the African late Miocene, a period during which the ancestral lines leading to modern African apes had begun to differentiate."


"Once again, it is Africa - particularly Ethiopia - that has yielded crucial evidence for evolution near the base of our family tree."


Jay Kelley, who studies primate teeth at the University of Illinois, told Nature that he is sceptical of the significance of the new finds.


Prof White countered: The foundation for the claim seems sound; a real tour-de-force of dental analysis. The other lineage (that was the common ancestor of the later chimps and hominid lines) has yet to be found. But hopefully, we're closing in on it from both ends."


He added: "This time - for the first time - we are getting a glimpse of what appears to be the dawn of the gorilla lineage.


"However, this great palaeontological news is tempered by the realisation that living gorillas, after ten million years of evolution, are now threatened by another evolutionary endpoint - modern humans."



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