"Earliest human ancestor discovered" 

     Researchers in Ethiopia have discovered the earliest human
     ancestor so far. They have unearthed the teeth, jawbone,
     collarbone, hand and foot bones of a creature who walked on
     two legs through cool, wet forests 5.8m years ago.

     Yohannes Haile-Selassie, a doctoral student at the University of
     California, and his colleagues report in Nature today that they
     found evidence of a creature they have provisionally named
     Ardipithecus ramidus kadabba in the Middle Awash region of the
     Afar desert of Ethiopia.

     So far, the fragments of 11 hominid skeletons more than 5m years
     old have been found. At least five belong to the new subspecies.
      
     No one can begin to guess what Ardipithecus may have looked like.
     There are no intact limb bones, and no skull, so no one can
     reconstruct a face or torso. But the animal may have been the 
     size of the modern chimpanzee. On the evidence of its teeth, it
     probably lived on fibrous roots and leaves.
          
     The teeth had characteristics found in all later human-like
     creatures, but not in fossil or living apes. This meant that the
     animal had evolved after the human lineage separated from that
     of the chimpanzee ancestors. The toe and fragments of leg bone
     clearly belonged to a creature that walked on two legs. 

     Until now, the earliest known hominid - called Ardipithecus
     ramidus - stalked the same part of the Horn of Africa 4.4m years
     ago. The latest discovery pushes human ancestry nearer to the
     so-called "missing link", the last common ancestor of humans
     and their nearest relatives, the chimpanzee.

     The Middle Awash is a dry, stony, heavily eroded landscape.
     But 6m years ago, it was probably 4,500ft higher, much cooler,
     wetter and covered with forest. The newly discovered hominid
     foraged for food alongside primitive elephants, horses, rhinos,
     rats, monkeys and perhaps 50 other kinds of mammal. Active
     volcanoes showered the territory with ash, and lava flows
     blocked rivers to form lakes. 

     "It is hard to imagine that life would go on normally under such
     hostile environmental conditions - Ardipithecus and the other
     animals were real survivors," said Giday Wolde Gabriel, of the
     Los Alamos national laboratory, who helped date the fossils. 

     The region has been a goldmine for researchers. Three decades
     ago, it yielded the famous skeleton of "Lucy" - a female who
     died 3.2m years ago. Seven years ago, it produced the first
     Ardipithecus. In 1997, it provided the first proof of stone tool
     use by human ancestors 2.5m years ago. In 1999, the US-Ethiopian
     team found a new human species called Australopithecus garhi,
     which lived on the same plain 2.5m years ago.
       
     But the story of how humans emerged from this African genesis is
     as murky as ever. "The fossils are strong evidence that lines 
     leading to chimpanzees and humans had split well before 5m years
     ago," said Mr Haile-Selassie. "No one thought we would find any
     hominids there at all. Now everybody is hoping we will find a
     skeleton." 

     Tim Radford, science editor
     Thursday July 12, 2001
     The Guardian 
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