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Ancient DNA Analysis Finds Three Migration Waves Shaped Genetic Ancestry of Vanuatu

NEW YORK – The population of Vanuatu was shaped by the influx of three groups with differing ancestral backgrounds, a new genetic study has found.

Vanuatu is an archipelago of dozens of islands that stretches for more than 620 miles in the South Pacific Ocean, where it has formed a key link between the Solomon Islands and New Caledonia. Humans settled in the region beginning about 3,000 years ago.

By analyzing ancient DNA isolated from bone or tooth samples of individuals who lived in various regions of Vanuatu during different eras, researchers led by Harvard Medical School's David Reich began to piece together the ancestry components that arrived with each wave of migration. As they reported in Current Biology on Thursday, the researchers found that the first wave of migrants during the Lapita period likely came from a source with East Asian ancestry, while a second wave of people arriving largely had Papuan ancestry. A third wave then came from a population with mostly Polynesian ancestry. 

"Our results outline three distinct periods of population transformations," Reich and his colleagues wrote in their paper.

The researchers generated genome-wide data for 11 ancient individuals from the island of Efate in central Vanuatu. Five were from Chief Roi Mata's Domain, a World Heritage Site consisting of three locations on Efate, Lelepa, and Artok. The researchers analyzed their new samples in combination with 26 previously published samples from Ni-Vanuatu individuals, eight other Oceanians, and a set of diverse present-day samples.

A principal components analysis largely separated the populations based on their proportion of First Remote Oceanian ancestry and on their similarity to either Solomon Island or New Guinea populations. The ancient individuals broadly overlapped in their ancestry with modern inhabitants of the same islands, though some older individuals exhibited a higher level of First Remote Oceanian ancestry.

Based on their population genetic analyses, the researchers found that the 12 individuals from the Lapita cultural complex, including four newly analyzed samples, had nearly entirely First Remote Oceanian-related ancestry. These samples dated back to between 3,000 and 2,500 years ago.

The source of the First Remote Oceanian-related ancestry is a population related to East and Southeast Asians. The researchers noted that while future analysis of additional samples could uncover greater genetic diversity from this period, their findings support the idea that the first people of Remote Oceania descended from a population related to East and Southeast Asians and spread the Lapita cultural complex.

Then about 2,500 years ago, a shift in genetic ancestry occurred, as a smaller proportion of First Remote Oceanian-related ancestry was found among post-Lapita samples. Instead, the researchers noted an influx of Papuan ancestry. Its source in Vanuatu, beginning 2,500 years ago and continuing to the present, is largely the same and is likely to be the island of New Britain and not the closer Solomon Islands, they reported.

The researchers suggested, based on both archeological and genetic findings, that this second migration event was largely a continuation of the first one from late-Lapita times but involved migrants with different ancestry.

Based on their analysis of samples from Chief Roi Mata's Domain from about 1600 AD, a third wave then brought in Polynesian-related ancestry as well as additional First Remote Oceanian-related ancestry. Additionally, present-day communities in central, though not southern, Vanuatu appear related to the Chief Roi Mata's Domain individuals, suggesting differing sources of Polynesian influence throughout Vanuatu.

"Thus, although the ancestry of present-day Ni-Vanuatu groups can largely be traced to the early human history of the archipelago, later migrations — in particular of Polynesians — have also contributed to the genetic diversity of Vanuatu today," the researchers wrote in their paper.