New Ethiopian Discovery sheds Light on Bipedalism in Ancient Hominids

The authors of a paper appearing in the scientific publication “The Proceedings of the National Academy of Sciences”, claim that a 3.58 million-year-old partial skeleton of an ancient human may help resolve the puzzle over just how bipedal were Australopithecus afarensis.

The new skeleton nicknamed “big man” by the research team comes from the Rift Valley in the central Afar of Ethiopia, about 200 miles north-east of Addis Ababa.  Discovered in 2005 by a team member, Alemayehu Asfaw, the bones were situated near the Mille River, a long day’s walk north of Hadar where the famous 3.2 million-year-old fossil skeleton A. afarensis known as “Lucy” was found.  “Big man” or “Kadanuumuu” in the local dialect, is estimated to be nearly 2 metres tall, much taller than Lucy and the limb bones and pelvis are helping scientists to understand how this ancient hominid walked and moved about.

Australopithecus afarensis

Commenting on the find, Owen Lovejoy, a palaeoanthropologist at Kent State University (Ohio) stated:

“This new skeleton shows a fully running and walking biped, with most of the adaptations we have.”

Lead author of the study, Yohannes Haile-Selassie from the Cleveland Museum of Natural History (Cleveland, Ohio) added:

“What we see in the new skeleton’s pelvis is what we see in modern humans.”

Lucy’s small frame caused some disagreement over earlier interpretations of bipedality, Owen Lovejoy contends, but “big man’s” size and adult age allow clearer comparisons with other hominid types.

The new find supports conclusions drawn last year about the even earlier bipedality of another Ethiopian hominid, Ardipithecus ramidus, which at a minimum of 4.4 million-years-old is the oldest hominid found so far.  A. ramidus wasn’t fully modern, however; it retained ape-like arms and feet, which Australopithecus afarensis specimens don’t have.

To read an article on the discovery of A. ramidus: Oldest Known Human-like Ape Unveiled.

But the new skeleton doesn’t answer all the questions about when hominids began walking upright.  Palaeoanthropologists and other scientists who have studied the fossil evidence have concluded that although this new skeleton suggests that A. afarensis were “adept and committed bipeds, they were not identical and biomechanically equivalent to people”.

Interestingly, studies of the shoulder blade (scapula), the oldest hominid shoulder blade known to date, indicate that the muscle structure was very similar to what we see in our own species.  This suggests that for A. afarensis their arboreal heritage from their ape-like ancestors was already very distant.

For models and replicas of prehistoric animals and ancient hominids: Prehistoric Animal Models and Ancient Humans.