How did Mary leakeys discover change in the modern understanding of prehistoric humans?

Mary Leakey's discoveries, such as the Laetoli footprints and the skull of Proconsul africanus, provided critical evidence for the theory of human evolution. They showed that upright walking predated the development of a large brain, challenging previous assumptions. This helped shift the focus from a linear progression of human evolution to a more complex, branching family tree of human ancestors.