Oldest Known Human Ancestor

In the October 2, 2009 issue of Science, scientists report on the discovery and reconstruction of the oldest known nearly complete skeleton of a female pre-human ancestor. Named Ardipithecus ramidus, “Ardi” stood only four feet tall and weighed about 110 pounds. Apparently she was a “facultative” biped, meaning that she could walk upright on the ground but was still able to climb and walk in trees.

The first bones of Ardipithecus ramidus were discovered in 1992, but it has taken this long to find and reconstruct enough of a skeleton to be confident enough to publish the results. And the results are stunning. At 4.4 million years old, Ardi pushes back the dawn of bipedalism by more than a million years. (“Lucy”, the celebrated Australopithecus afarensis shown on p. 518 of Human Biology, 5^th ed., is 3.2 million years old).

It’s the biggest find in decades. You can find 11 scientific articles on Ardipithecus ramidus in Science online. For a summary, read the Perspectives article by Ann Gibbons entitled “A new kind of ancestor: Ardipithecus unveiled”.