ON ITS OWN TWO FEET

KENYAN FOSSILS SUGGEST A NEW, EARLIER DATE WHEN A HUMAN ANCESTOR FIRST WALKED UPRIGHT

It is one of the fundamental mysteries of human evolution. When did the first apelike creatures begin to walk upright? Scientists believe this transformation probably occurred between 4 million and 6 million years ago, but until recently they had no fossils to back up their hypothesis. In 1994 researchers reported that they had found teeth and other fragments of a 4.4 million-year-old hominid in Ethiopia. But without key bones from below the waist, they could not say for sure how the animal moved.

Now, less than a year later, another team of paleontologists, led by Meave Leakey from the National Museums...

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