3.6 million-year-old relative of 'Lucy' discovered: Early hominid skeleton confirms human-like walking is ancient

Haile-Selassie is the first author of the initial analysis of the specimen, which will be published in the online early edition of the Proceedings of the National Academy of Sciences during the week of June 21, 2010.

The partial skeleton belongs to "Lucy's" species, Australopithecus afarensis. It was found in the Woranso-Mille area of Ethiopia's Afar region by a team led by Haile-Selassie that excavated of the skeleton over five years following the discovery in 2005 of the lower arm bone. The team recovered the most complete clavicle and one of the most complete shoulder blades ever found in the human fossil record. A significant portion of the rib cage was also found.

The specimen was nicknamed "Kadanuumuu" (kah-dah-nuu-muu) by the authors. This means "big man" in the Afar language and reflects its large size. The male hominid stood between 5 to 5 ½ feet tall, while "Lucy" stood only 3 ½ feet tall.

"This individual was fully bipedal and had the ability to walk almost like modern humans," said Haile-Selassie. "As a result of this discovery, we can now confidently say that 'Lucy' and her relatives were almost as proficient walking on two legs as we are, and that the elongation of our legs came earlier in our evolution that previously thought."

He explained, "All of our understanding of Australopithecus afarenis' locomotion was dependent on 'Lucy.' Because she was an exceptionally small female with absolutely short legs, this gave some researchers the impression that she was not fully adapted to upright walking. This new skeleton falsifies that impression because if 'Lucy's' frame had been as large as this specimen, her legs would also have been proportionally longer."

Kent State University Professor Dr. C. Owen Lovejoy was a co-author of the research and helped analyze the skeleton. When comparing it to "Lucy," Lovejoy said, "They both have pelves, a complete lower limb bone and elements of the forelimb, vertebral column and thorax. However, the new specimen has more complete ribs and a nearly complete scapula, which tells us much more about body form in Australopithecus afarensis than 'Lucy' was able to alone."

Authors of the research include Cleveland scientists Dr. Bruce Latimer, interim director of the Center for Human Origins of the Institute for the Science of Origins at Case Western Reserve University, and Dr. Beverly Saylor, associate professor of geological sciences at Case Western Reserve University. Other co-authors are from Addis Ababa University in Ethiopia, Berkeley Geochronology Center and Stanford University.

Australopithecus afarenis is the best-known direct early human ancestor. Until now, the only partial skeleton assigned to this species was "Lucy," a 3.2 million-year-old female individual, which was discovered in 1974 by a team led by then Museum curator Dr. Donald Johanson.

The analysis of "Kadanuumuu" indicates that the shoulder and rib cage of this species were different from those of chimpanzees. "These findings further confirm what we concluded from the 'Ardi' specimen -- that chimpanzees have undergone a great deal of specialized evolution since we shared a last common ancestor with them," said Lovejoy.

"Ardi," or Ardipithecus ramidus is a 4.4 milion-year-old hominid species that was unveiled in October 2009 by a team that included Haile-Selassie, Lovejoy, and Museum scientists and associate researchers Dr. Linda Spurlock, Dr. Bruce Latimer and Dr. Scott Simpson. "Ardi" was named by the journal Science as breakthrough discovery of the year. Click here to find out more about "Ardi."