The Knee Joint From Hadar
The discovery in November 1974 of a nearly complete, three million year old skeleton, nicknamed “Lucy”, overshadowed a quite remarkable find twelve months before. In 1973, Donald Johanson found two fragments of fossilized bone, the proximal or near end of a tibia and the distal or far end of a femur, otherwise known as a shinbone and thighbone, which together form the knee. The distal end of the femur in a biped has a distinctive shape, differing from the shape of a chimp or gorilla femur, for example.
When this find – “the knee joint” - was dated at three million years, Johanson knew he had found the oldest (at that time) evidence of bipedality. “Lucy” confirmed this a year later. Being a more spectacular find, Lucy caused us to lose sight of how groundbreaking was the discovery of the knee joint.