Tracing the Austronesian Expansion Through Language and Genetics
The indigenous Taiwan tribe Amis share close Y-Chromosome affinities with Polynesian populations as far out as Aotearoa.
The Austronesian language family, one of the largest and most widely dispersed in the world, has long fascinated linguists and geneticists alike. Its speakers, who today number over 380 million, are spread across a vast swath of the globe, from Madagasicara in the west to Rapa Nui in the east. But where did this remarkable expansion begin, and how did it unfold?
Recent research by Javier Rodriguez Lui et al. combining linguistic and genetic evidence is shedding new light on these questions. By studying the distribution and diversity of key genetic markers, scientists are piecing together a clearer picture of the migratory paths taken by the ancestors of today's Austronesian speakers.
One such marker is the Y-chromosome sub-haplogroup O2a2b-P164. Moderate to high frequencies of this lineage are found among the indigenous Amis people of Taiwan, as well as in parts of the Philippines, Micronesia, and Western Polynesia. Crucially, diversity within the haplogroup decreases with increasing distance from Southeast Asia, suggesting a gradual expansion outward from this region.
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High-resolution sequencing of O2a2b-P164 Y-chromosomes paints an even more detailed picture. The data point to an origin for the lineage around 19,000 years ago, likely in mainland Southeast Asia. Then, approximately 4,700 years ago, the haplogroup split into three distinct branches: one localized to Southeast Asia, one to Taiwan (represented by the Amis), and one that would go on to predominate in what are called Micronesia and Polynesia today.
This timeline aligns with the leading linguistic model for the Austronesian expansion, which proposes a progression from Taiwan to the Philippines and Indonesia beginning around 5,000 years ago, followed by a rapid spread into the previously uninhabited islands of Oceania. The relative homogeneity of O2a2b-P164 lineages in Polynesia and Micronesia suggests this final phase occurred in quick pulses, with founder effects and genetic drift leading to the high frequencies observed in some populations.