The Japan Times, May 18, 1998
By PATRICK RIZZO
Evidence dates earliest walking hominids
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 4 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.
"These tests basically remove any doubt that the origins of bipedalism go back well over 4 million years," said Craig Feibel, a Rutgers University geologist, in a phone interview.
Feibel coauthored the article with Meave Leakey of the National Museums of Kenya, Ian McDougall of Australia National University, Carol Ward of the University of Missouri and Alan Walker of Penn State University.
Feibel said the new findings also would lay to rest concerns in the scientific community that the fossils they had named Australopithecus anamensis actually were from two different types of hominids, or members of the human family.
The teeth and jaws of anamensis were found at different layers of rock (in Kanapoi, southwest of Lake Turkana in northern Kenya, and Allia Bay, east of the lake) from the rest of the skeleton, raising doubts that they were from the same species.
The jaw and teeth are very apelike, with parallel tooth rows, unlike human jaws, which widen as you go back. A partial fossil found of a tibia, one of the larger leg bones, shows strong evidence of bipedality, however, and a lower humerus (or arm bone) is very like modern man's.
The tests, done on volcanic matter in layers above the limb bones, yielded dates of 4.07 million years ago, leading to the conclusion that fossilized bones found in layers below were older, Feibel said.
"It wasn't until 1996 that we discovered materials in this layer that we could actually date," Feibel said. "The age proves that there is only a very short interval of time represented by the fossils, and essentially they are all very old; so in a sense, that supports their all being from the same species."
Anamensis, therefore, was a very unusual primate, a sort of intermediate between man's older, apelike ancestors and modern humans. It had humanlike limbs, apelike jaws and teeth and a small brain.