How did Stone Age people reach North and South America? Dr Alice Roberts discovers evidence for an ancient corridor through the Canadian ice sheet that may have allowed those first people through. But some very ancient finds in southern Chile seem to suggest a very different way into the Americas; an ancient human skull discovered in Brazil even points to an Australasian origin of the Americans. Could a route from Australia across the Pacific have been possible?

• Alice Roberts
• Tessa Wojtczak