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From David Perlman:

In the Afar language of Ethiopia, he's called Kadanuumuu, and to the Ethiopia-born anthropologist who found his bones, he could be called "Big Man," or even "Big Guy."

But to everyone else interested in the discovery of new fossil evidence for the ancestry of the human lineage, he'll be known as "Lucy's great-grandfather."

A team of noted fossil hunters reports this week the discovery of a creature in the same species as Lucy, but at least 400,000 years older than that famed female whose discovery in 1974 was hailed as a major step in piecing together the story of human evolution.

From the newfound fossils, their leading discoverer says scientists have determined that the creature - nicknamed Kadanuumuu, but known scientifically as Australopithecus afarensis - walked upright on two feet. It means that bipedalism was fully established as a normal way of life in human ancestry at least 3.58 million years ago, when this remote forebear lived.

The finding is reported in the current issue of Proceedings of the National Academy of Sciences.

Yohannes Haile-Selassie, director of anthropology at the Cleveland Museum of Natural History who earned his doctorate at UC Berkeley, led the international team of fossil hunters in Ethiopia's arid Afar Desert that discovered evidence of the creature in 2005. They first found its single lower arm bone and kept digging for five more years before they assembled enough bones to identify it.

Its nickname, Kadanuumuu, is Afar for big and male.

In all, the scientists unearthed a left leg, a shoulder, a collarbone, a pelvis and parts of the rib cage - altogether about 40 percent of the entire skeleton, Haile-Selassie said.

Donald Johanson, Lucy's discoverer and now founding director of the Institute for Human Origins at Arizona State University in Tempe, called the "grandfather" report intriguing and, recalling the many recent discoveries of Lucy's fossil relatives, said: "This is really a remarkable time in the history of paleoanthropology."

Johanson noted that although Lucy was tiny - about 3 1/2 feet tall - Kadanuumuu was much larger - about 5 or 5 1/2 feet tall.

The size difference between Lucy, who lived 3.2 million years ago, and her "great-grandfather," is known as sexual dimorphism and is true for humans today, although the wide divergence in size of the two fossils is typical of those early creatures that still bore more traces of their descent from the ape lineage, Johanson said.

"The pelvis in both creatures is very advanced," said Owen Lovejoy, a co-author of the report by Haile-Selassie's group and one of the world's foremost experts on fossil anatomy. "There's a deep groove that shows they were pretty good runners. They had clearly evolved to walk very much as humans do, and to run fast without pulling a hamstring muscle."

Lovejoy also analyzed the bones of Lucy and "Ardi," the much earlier creature who lived some 4.2 million years ago - much closer to the unknown time in evolution when the lineages of humans and apes split from a "last common ancestor."

Ardi - Ardipithecus ramidus - was reported only last year by a team headed by Tim D. White of UC Berkeley who worked with Johanson on the discovery of Lucy more than 35 years ago. Ardi, who lived 4.4 million years ago, walked on two feet, but also climbed trees and was a much earlier arrival on the winding evolutionary pathways that led to all the hominids before us, Homo sapiens.