ADDIS ABABA, Ethiopia — U.S. and Ethiopian scientists have discovered the fossilized remains of what they believe is humankind's first walking ancestor, a hominid that lived in the wooded grasslands of the Horn of Africa nearly 4 million years ago.
The bones were discovered in February at a new site in Mille, in the northeastern Afar region of Ethiopia, said Bruce Latimer, director of the Cleveland Museum of Natural History in Ohio. They are estimated to be 3.8 million to 4 million years old.
The fossils include a complete tibia, parts of a thighbone, ribs, vertebrae, a collarbone, pelvis and a complete shoulder blade.
There also is an ankle bone which, with the tibia, proves the creature walked upright, said Latimer, co-leader of the team that discovered the fossils.
The bones are the latest in a growing collection of early human fragments that help explain the evolutionary history of man.
"Right now we can say this is the world's oldest bipedal," Latimer said. "This new discovery will give us a picture of how walking upright occurred."
Paleontologists previously discovered in Ethiopia the remains of Ardipithecus ramidus, a transitional creature with significant ape characteristics dating as far back as 4.5 million years.
There is some dispute over whether it walked upright on two legs, Latimer said.
Scientists know little about A. ramidus.
A few skeletal fragments suggest it was even smaller than Australopithecus afarensis, the 3.2-million-year-old species widely known by the nearly complete "Lucy" fossil, which measures about 4 feet tall.
Scientists have yet to classify the new find, which they believe falls between A. ramidus and A. afarensis.
The specimen was found after two months of excavation at Mille, 37 miles from the famous Lucy discovery.