Rat DNA clues to sea migration This carving shows Pacific rats on the face of a Polynesian ancestor Scientists have used DNA from rats to trace migration patterns of the ancestors of today's Polynesians. People are thought to have arrived in Polynesia, comprising the Pacific islands of Fiji, Tonga and Samoa, by boat some 3,000 years ago. Rat data suggests the journey was more complex than the popular "Express Train" theory, which proposes a rapid dispersal of people from South Asia. Details appear in Proceedings of the National Academy of Sciences. Elizabeth Matisoo-Smith and Judith Robins from the University of...