Fossils Indicate Human Ancestor Walked Erect More Than 4 Million Years Ago

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 4 million years ago. In an article in today’s issue of the 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 and 4.12 million years, pushing the emergence of walking on two legs back more than 500,000 years.

The new species, called Australopithecus anamensis, has primitive jaws, shaped more like a chimpanzee’s than like a modern human’s. It also shows large differences in size between the sexes in overall body parts and differences in shape for certain body parts, such as teeth. A wrist bone has the primitive features of a chimpanzee, while leg bones are more like a modern human’s, allowing the creature to walk upright.

Compiled by Times medical writer Thomas H. Maugh II