One warm, sunny day in November of 1974, anthropologist Donald Johanson was walking through the desert of Hadar, Ethiopia when he came across the elbow bone of a skeleton, slightly protruding to the surface. Johanson took the bone back to his camp and began to analyze it with colleagues. He soon realized that he had more than just a single elbow bone, but a number of bones, all from the same skeleton.
Johanson returned to the site of discovery and dug up more and more bones, all of which he believed belonged to a single hominid. He called in experts on bone structure and locomotion and then began to determine conclusions based on the findings that these experts were making. Johanson believed that Lucy, as he has come to call his skeleton, was the oldest human ancestor, at 3.2 million years old. She was the most complete hominid skeleton ever found with 40 % of her skeleton having been recovered.
Lucy was also the best preserved skeleton of a hominid, with her bones in excellent condition. But most important was Johanson’s claim and reason for putting her in the lineage of humans, which was that she was bipedal (walked upright, on two feet). This claim was based on evidence supplied by Johanson, locomotion expert Owen Lovejoy, and many other experts in various fields, and they were well-supported and have changed the way we interpret human evolution.
The most remarkable discovery about Lucy, that went along with her being bipedal, was that her brain size was very small. It was about a third of the size of humans, and much closer in size to that of apes. This was a crucial discovery, because before finding Lucy, it was commonly believed that brain growth occurred in apes first and then, only after that, did apes start to walk upright and develop more human characteristics. These beliefs held that once hominids started to walk upright, their hands were suddenly free to start making tools, weapons, and carrying food back for others.