http://www.cnn.com/TECH/science/9805/06/science_humans.reut/
Excerpt:
Evidence found dating earliest known erect humans
May 6, 1998
Web posted at: 3:21 PM EDT (1521 GMT)
NEW YORK (Reuters) - A group of scientists say they have conclusive evidence
that fossils they discovered in Kenya in 1995 are from the earliest known
ancestor of man to walk erect, more than four million years ago.
In an article published in the May 7 issue of the British journal Nature,
the scientists said tests on volcanic material from the area of the find
confirm the fossils' age at between 4.07 million years to 4.12 million
years, pushing the emergence of walking on two legs back more than 500,000
years.
....