Ten years on from making her landmark BBC2 series, The Incredible Human Journey, Alice Roberts explores the latest insights into the colonisation of the globe by our ancient forebears. Sometimes racing along coastlines, at other times, coming to a standstill, with any advance blocked by great walls of ice, our ancient ancestors gradually spread right across the globe. Along the way, they adapted to a huge range of different environments, learning to live everywhere - from tropical forests and temperate shorelines to the high Arctic. In the last ten years, the evidence has piled up: new fossils, archaeological sites and astounding insights from genetics have painted a new picture of these ancient journeys, and the challenges overcome by our Stone Age ancestors.