The stunning 1974 discovery oered proof that ancient hominins were walking around on two feet some 3.2 million years ago.
On November 24, 1974, paleoanthropologist Donald Johanson was looking for something very specic in the gravel-strewn landscape of northeastern Ethiopia. A year earlier, Johanson and a colleague had made a thrilling discovery in the very same region—a perfectly preserved knee joint from an ancient human that walked those hills 3.4 million years ago. That was nearly a million years older than the oldest known human fossil at the time.