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Population Study Points to Distinct Genetic, Language Trajectories for Remote Oceania

NEW YORK (GenomeWeb) – A new analysis of ancient and contemporary genomes from Oceania suggests that remote South Pacific island populations have retained the ancestral Austronesian language brought to Remote Oceania by East Asian ancestors, although Papuan populations arriving over the past 2,500 years or so have since replaced the early populations.

"The demographic history suggested by our ancient DNA analyses provides really strong support for this historical linguistic model, with the early arrival and complex, incremental process of genetic replacement by people from the Bismarck Archipelago," co-senior author Adam Powell, an archaeogenetics, linguistic, and cultural evolution researcher at the Max Planck Institute for the Science of Human History, said in a statement. "This provides a compelling explanation for the continuity of Austronesian languages despite the almost complete replacement of the initial genetic ancestry of Vanuatu." 

As they reported online today in Nature Ecology & Evolution, Powell and colleagues from centers in Germany, France, Australia, and elsewhere did targeted, genome-wide sequencing on 19 ancient samples from sites in Vanuatu, Tonga, French Polynesia, and the Solomon Islands using samples that were between a few hundred- and nearly 3,000 years old. They also genotyped 27 ni-Vanuatu individuals from modern-day Oceania, analyzing the modern and ancient sequences in concert with available SNP and/or whole-genome sequence profiles for hundreds more individuals from Oceania and East Asia.

Prior studies suggest that Austronesian explorers, likely venturing from East Asia, began peopling the Remote Oceanic islands such as the Santa Cruz Islands, Vanuatu, New Caledonia, and Fiji thousands of years ago. But there are still many unanswered questions about the complex historical interactions between Austronesian and non-Austronesian language-speaking populations in Near and Remote Oceania.

Along with complete mitochondrial genome sequences for these ancient individuals, the team extracted information at roughly 1.24 million nuclear genome SNPs in the 19 ancient samples from Remote Oceania, ranging in age from roughly 2,600 to 200 years old, using hybridization sequencing and Illumina HiSeq 4000 sequencing.

The researchers also used the Axiom Genome-Wide Human Origins array to genotype 27 ni-Vanuatu individuals from the Malakula and Efate islands and did low-coverage shotgun sequencing on eight of those participants.

Together with existing genotyping and/or genome sequence data for hundreds of modern day individuals from Remote Oceania, Near Oceania, East Asia, and beyond, the new SNP profiles provided a clearer look at Remote Oceania's population history. In particular, the team noted that the earliest population on Vanuatu largely clustered with East Asian and Austronesian populations — a Remote Oceanic population that appears to have been replaced by populations clustering more closely with Near Oceanic-Papuan populations starting some 2,500 years ago.

Although the precise population dynamics differed somewhat between Remote Oceanic islands, the researchers saw signs of earlier-than-anticipated Papuan ancestry in the region, coupled with a slow and steady shift that did not seem to be accompanied by widespread language replacement.

"Population replacement with language continuity is extremely rare — if not unprecedented — in human history," Powell and his co-authors concluded. "Our analyses show that rather than one large-scale event, the process was incremental and complex, with repeated migrations and sex-biased admixture with peoples from the Bismarck Archipelago."