Bed I, the oldest, is about 2 million years old. From the late 1930s, Louis and Mary Leakey found stone tools in Olduvai and elsewhere, found several extinct vertebrates, including the 25-million ...

When Louis Leakey and Mary Nicol first met, he asked her to help with illustrations for his upcoming (1934) book Adam's Ancestors: An Up-to-Date Outline of What is Known about the Origin of Man.