PhysOrg.com—Scientists from The Cleveland Museum of Natural History, Kent State University, Case Western Reserve University, Addis Ababa University and Berkeley Geochronology Center were part of an international team that discovered and analyzed a 3.6 million year old partial skeleton found in Ethiopia. It’s only the second partial skeleton of A afarensis to be recovered. Renowned Ethiopian fossil hunter Alemayehu Asfaw found the first element of “Kadanuumuu” in February 2005 at Korsi Dora, about 210 air miles northeast of the Ethiopian capital Addis Ababa. The specimen was exposed on the surface and further investigation resulted in the recovery of more elements.
Excavations between 2005 and 2008 uncovered an upper arm, a collarbone, neck bones, ribs, pelvis, sacrum, a thighbone, a shinbone and the shoulder blade. Excavations took more than five years to complete. 400,000 years older than the famous “Lucy” skeleton, its remains provide conclusive proof that A afarensis could walk upright freely without the use of its hands. Advanced upright walking, like that of modern humans, occurred much earlier than previously thought.
The partial skeleton belongs to “Lucy’s” species, Australopithecus afarensis, found in the Woranso-Mille area of Ethiopia’s Afar region by a team led by Dr Yohannes Haile-Selassie, Curator and Head of physical anthropology at The Cleveland Museum of Natural History. It was excavated over five years after the discovery of a fragment of the lower arm bone in 2005. The excavation recovered the most complete clavicle and one of the most complete shoulder blades ever found in the human fossil record.
The specimen was nicknamed “Kadanuumuu”, meaning “big man” in the Afar language, indicating its size. The male hominid was between 5 feet; and 5 feet 6 inches tall, while “Lucy” was only about 3 feet 6 inches. “Kadanuumuu” appears to be in good agreement with fossilized footprints dated to about 3.6 million years ago and discovered in Laetoli, a site in Tanzania in eastern Africa. The footprints show that early human ancestors habitually walked upright; there are no knuckle-impressions or signs of abducted toes. Haile-Selassie said:
The KSD skeleton is long sought fossil evidence. It complements the Laetoli footprints and incontrovertibly shows A afarensis was an obligate bipedal since its first appearance in the fossil record. This individual was fully bipedal and could walk almost like modern humans. We can now confidently say that “Lucy” and her relatives were almost as proficient as we are walking on two legs, and that the elongation of our legs came earlier in our evolution than previously thought.
KSD is shorthand for “Korsi Dora”, the name of the locality where the skeleton was found. Co-author Dr C Owen Lovejoy, Kent State University professor of anthropology, explained:
The new specimen tells us much more about the pelvis, thorax, and limb proportions than “Lucy” did alone.
Previous examinations of Lucy led some scientists to conclude A afarensis was not fully adapted to upright walking, partly from her short stature. Long legs are a characteristic of bipedalism. “Kadanuumuu” has most of the same skeletal parts as Lucy and others never previously known, including a significant portion of the rib cage and a nearly complete adult shoulder blade. Before now anthropologists concluded evolutionary ancestors had shoulders more like those of chimpanzees. But “Kadanuumuu” surprised researchers by revealing a shoulder very different from chimpanzees, which are thought to be the closest living relatives of Homo sapiens. Haile-Selassie explained:
Kadanuumuu’s shoulder was also a major discovery. It shows that our ancestor’s shoulder blade and rib cage were much more similar to those of modern humans than previously had been thought. This tells us that chimpanzees have evolved a great deal since we shared a last common ancestor with them.
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