A detailed study of DNA of Pacific Islanders finds that their mitochondrial DNA were present in Island Southeast Asia from an earlier period than the so-called Austronesian expansion, and suggests a more complex picture of how humans migrated into the Pacific.

Resolving the ancestry of Austronesian-speaking populations
Soares et al.
Human Genetics, DOI 10.1007/s00439-015-1620-z

New research into the origins of the Austronesian languages
Eureka Alert, 28 January 2016

There are two very different interpretations of the prehistory of Island Southeast Asia (ISEA), with genetic evidence invoked in support of both. The “out-of-Taiwan” model proposes a major Late Holocene expansion of Neolithic Austronesian speakers from Taiwan. An alternative, proposing that Late Glacial/postglacial sea-level rises triggered largely autochthonous dispersals, accounts for some otherwise enigmatic genetic patterns, but fails to explain the Austronesian language dispersal. Combining mitochondrial DNA (mtDNA), Y-chromosome and genome-wide data, we performed the most comprehensive analysis of the region to date, obtaining highly consistent results across all three systems and allowing us to reconcile the models. We infer a primarily common ancestry for Taiwan/ISEA populations established before the Neolithic, but also detected clear signals of two minor Late Holocene migrations, probably representing Neolithic input from both Mainland Southeast Asia and South China, via Taiwan. This latter may therefore have mediated the Austronesian language dispersal, implying small-scale migration and language shift rather than large-scale expansion.

Paper is open access, downloadable here.