mtDNA lineage analyses: origins and migrations of Micronesians and Polynesians

The islands of Micronesia and Polynesia collectively comprise the last major region of the globe to be settled by humans. Both of these groups of islands were colonized within the last 4,000 years by Austronesian-speaking agriculturists. Based on biogeographic and linguistic patterns, central-eastern Micronesia and Polynesia are included by many in a single category called Remote Oceania. Similarities of biologic, linguistic, and cultural traits within Remote Oceania highlight a question central to Oceanic studies: Are similarities among islands due to a common origin of isolated communities, to ongoing interactions among islands, or both? Analyses of mitochondrial DNA (mtDNA) sequences reveal that most remote Oceanic populations are polyphyletic. These polyphyletic populations violate the assumptions of many genetic distance and population demography models and so are problematic to interpret. The majority of mtDNA sequences from Micronesian and Polynesian populations are derived from Asia, whereas others are inferred to have originated in New Guinea. These data support an Island Southeast Asian origin and a colonization route along the north coast of New Guinea. The Marianas and Yap proper (main island) appear to have been independently settled directly from Island Southeast Asia, and both have received migrants from Central-Eastern Micronesia since then. Palau clearly demonstrates a complex prehistory including a significant influx of lineages from New Guinea. Thus genetic similarities among Micronesian and Polynesian populations result, in some cases, from a common origin, and in others, from extensive gene flow.