TheMillerCircle.org

Meet our long extinct cousin–Ardipithecus ramidus or “Ardi,” a female who happens to be the newest and oldest member of the human ancestor tree.  In the December 18 2009 issue of Science Magazine, the editors named the discovery of Ardi, whose fossilized remains date back 4.4 million years, as the scientific breakthrough of the year. This must have been a challenge for the editors of Science, as the papers first describing the investigative work on Ardi were all published in Science Magazine in 2009 in the form of 11 papers, with 47 researchers from nine different countries, collaborating to not only analyze the fossil bones of Ardi, but further characterize an additional 150,000 fossil specimens from the same dig site, located in the Afar Depression of Ethiopia. The results represent 15 years of labor-intensive investigations and extensive collaborations. While many of the insights and conclusions derived from this study have been challenged by other researchers,  no one has challenged the age, significance or authenticity of the finding. Until Ardi was discovered in 1994, our oldest hominin fossil was the famous Lucy (Australopithecus afarensis), discovered in 1974. Lucy was 3.2 million years in age, so the discovery of Ardi was a major step backward in time. And, Ardi is more transitional and primitive than Lucy.

Hominin is meant to describe all humans and human ancestors exclusive of those related to modern apes. You can learn about the various distinctions among humans and other primates here. The single requirement legitimizing membership in the hominin club is that of walking erect, as we do. Many clues point to an erect posture for Ardi, including skull changes, hand differences and pelvis structure. Ardi’s pelvis was not well preserved, so some doubt about this not so subtle feature, makes the story incomplete, or at least less certain. You can watch a video discussion among the scientists who described the original findings here. One distinctive feature of Ardi is the structure of the foot, which had an opposable toe, suggesting that she was at home swinging from tree branches grasped with her feet or hands. Thus Ardi, only slightly larger than a chimpanzee, was in transition between a pure tree dweller and a non-tree dwelling, erect-walking hominid. Ardi had a brain only slightly larger than that of  a chimpanzee, a fact that researchers take to mean our ancestors learned to walk upright before our brains acquired their large, modern size. Extensive analysis of the fossil record from the dig site suggests that Ardi hung out in an ancient floodplain, covered in woodlands, as she climbed among hackberry, fig and palm trees and lived among monkeys, kudu antelopes and peafowl. Do you see any similarity between Ardi and the features of known, living hominids of today? I think I have a direct descendant as one of my neighbors.