Who are we? Where do we come from? What does it mean to be human? For thousands of years, such questions have been explored through philosophy and religion, but the answers now seem to lie firmly within the grasp of an empirical approach to the world and our place within it. By peering deep into our past and dragging clues out into the light, science can now provide us with some of the answers to the questions that people have always asked. From the first spark of life on earth 3.8 billion years ago, we track the evolution and connectivity of all living things. Follow in the footsteps of our ancestors from Africa into Asia and around the Indian coastline, to Australia, north into Europe and Siberia, and, eventually, to the last continents to be peopled: the Americas. Examine the sophistication of some of the earliest civilisations, and we’ll discuss how we know what we know and why we think what we think, what science can tell us. This is the story of us, from single cell to civilisation.