Fossils discovered in Kenya in 1995 are from the earliest known ancestor of man to walk erect -- more than four million years ago, a group of scientists said. Tests on volcanic material from the area 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.

Human-like limbs, ape-like jaws
http://cnn.com/TECH/science/9805/06/science_humans.reut/