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Hunter-gatherer occupations of small islands are rare in world prehistory and it is widely accepted that island settlement is facilitated by agriculture. The Ryukyu Islands contradict that understanding on two counts: not only did they have a long history of hunter-gatherer settlement, they also have a very late date for the onset of agriculture, which only reached the archipelago between the 8th and 13th centuries AD. Here, we combine archaeology and linguistics to propose a tripartite model for the spread of agriculture and Ryukyuan languages to the Ryukyu Islands. Employing demographic growth, trade/piracy and the political influence of neighbouring states, this model provides a synthetic yet flexible understanding of farming/language dispersals in the Ryukyus within the complex historical background of medieval East Asia. Introduction Methods Results - Archaeological Approach -- Demographic growth -- Trade/piracy -- State intervention - Linguistic Approach -- Linguistic inferences about the most probable tree structure -- Linguistic inferences about the most probable homeland of Proto-Ryukyuan -- Linguistic inferences about the most probable break-up time of Proto-Kyushu-Ryukyuan -- Inferences about the most probable linguistic outcome of the migration Discussion Conclusions

We investigated the genetic structure among populations of the Ryukyu wild boar (Sus scrofa riukiuanus) on Tokunoshima Island by analyzing DNA from modern and archaeological samples. Four and two mtDNA haplotypes were found in the modern and archaeological samples, respectively. One haplotype was shared between the modern and archaeological samples. Of the seven haplotypes, four were only found on Tokunoshima. These haplotypes were genetically close to each other and classified as those from the Ryukyu wild boars. This genetic similarity between modern and archaeological samples suggests that these four haplotypes originated from Tokunoshima. The chronology of the archaeological samples suggests that the genetic structure of the wild boar population on Tokunoshima has been maintained for over 1000 years. The representative glucosephosphate isomerase-processed pseudogene (GPIP) allele for the modern population on Tokunoshima was GPIP*3a and was found in a Ryukyu wild boar in a previous study. We detected three modern individuals that were genetically distinct from the Ryukyu wild boars based on mtDNA and GPIP analyses. They all had a different combination of the mtDNA haplotype and GPIP allele from each other. Our results indicate that gene flow events from pigs to wild boars have occurred on Tokunoshima.