S1, E1: Ian Thorpe, Ernie Dingo and Julia Zemiro are setting out on an extraordinary experiment. They're about to become some of the first people in Australia to use DNA to go on a journey tracing their ancestry back through more than 200,000 years. Guiding the trio on their journey is Dr John Mitchell. Dr Mitchell has spent more than 40 years studying genetics and what it tells us about our identity. But how can this journey of genetic time travel be plotted? The Y and Mitochondrial DNA on our fathers and mothers lines passes from generation to generation as exact copies. But every so often, a mutation occurs - a marker. These markers denote a new branch of the human family tree and the great journey of humankind. And crucially they can plot where Ian, Julia and Ernie's ancestors were and when. The trio heads towards the Serengeti plains in northern Tanzania. They're stepping back 200,000 years to the beginnings of humankind.