Homo sapiens is the most successful, the most widespread and the most influential species ever to walk the Earth. In the blink of an evolutionary eye we have spread around the globe, taken control of Earth's biological and mineral resources, transformed the environment, discovered the secrets of the universe and travelled into space. Yet just 7 million years ago, we were just another species of great ape making a quiet living in the forests of East Africa. We do not know exactly what this ancestor was like, but it was no more likely than a chimpanzee or gorilla to sail across the ocean, write a symphony, invent a steam engine or ponder the meaning of existence. How did we get from there to here?