The earliest colonization of oceanic islands by Homo sapiens occurred about 50,000–30,000 years ago in the tropical and temperate waters of the western Pacific, yet how this was achieved remains unclear. Under the experimental archaeology program called 'Holistic Reenactment Project of Voyages 30,000 Years Ago', we designed, built, and tested reed-bundle rafts as one of the candidate seagoing crafts in Paleolithic East Asia. Two rafts made by the best locally available reed, Typha domingensis, showed excellent stability and buoyancy at sea, but lacked mobility, speed, and durability required to cross fast-flowing seas in the Ryukyu Islands, southwest Japan. This supports the hypothesis that the first Ryukyu islanders used more sophisticated watercrafts to reach these islands about 35,000 years ago. [ABSTRACT FROM AUTHOR]