mtDNA lineage analyses: origins and migrations of Micronesians and Polynesians

The islands of Micronesia and Polynesia collectively comprise the last majo r region of the globe to be settled by humans. Both of these groups of isla nds were colonized within the last 4,000 years by Austronesian-speaking agr iculturists. Based on biogeographic and linguistic patterns, central-easter n 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 D NA (mtDNA) sequences reveal that most remote Oceanic populations are polyph yletic. These polyphyletic populations violate the assumptions of many gene tic distance and population demography models and so are problematic to int erpret. The majority of mtDNA sequences from Micronesian and Polynesian pop ulations are derived from Asia, whereas others are inferred to have origina ted 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-E astern Micronesia since then. Palau clearly demonstrates a complex prehisto ry 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. (C) 2000 Wiley-Liss, Inc.