Even with modern airplanes and ships, the far-flung islands of Tonga, Samoa, Hawaii, Micronesia and Fiji are difficult to reach. Thousands of years ago, the seafarers who first settled the islands had a much more arduous journey, sailing thousands of kilometers and navigating by the stars. According to a new study, these intrepid travelers may have gotten a boost from weather associated with El Niño-Southern Oscillation patterns, which sweep through the Pacific every three to seven years.