Patterns of prehistoric human mobility in Polynesia indicated by mtDNA from the Pacific rat

Human settlement of Polynesia was a major event in world prehistory. Despit e the vastness of the distances covered, research suggests that prehistoric Polynesian populations maintained spheres of continuing interaction for at least some period of time in some regions. A low level of genetic variatio n in ancestral Polynesian populations, genetic admixture (both prehistoric and post-European contact), and severe population crashes resulting from in troduction of European diseases make it difficult to trace prehistoric huma n mobility in the region by using only human genetic and morphological mark ers. We focus instead on an animal that accompanied the ancestral Polynesia ns on their voyages. DNA phylogenies derived from mitochondrial control-reg ion sequences of Pacific rats (Rattus exulans) from east Polynesia are pres ented. A range of specific hypotheses regarding the degree of interaction w ithin Polynesia are tested. These include the issues of multiple contacts b etween central east Polynesia and the geographically distinct archipelagos of New Zealand and Hawaii. Results are inconsistent with models of Pacific settlement involving substantial isolation after colonization and confirm t he value of genetic studies on commensal species for elucidating the histor y of human settlement.