Who were the first people in the Pacific?

Published: Tue 4 Oct 2016 11:05 AM
Tuesday, October 4, 2016
Who were the first people in the Pacific?
New research looking into the DNA of the earliest ancestors of Māori has confirmed that the first people to settle in the Pacific were from Asian farming groups rather than having a suspected Papuan ancestry.
According to research co-authored by Massey University Professor Murray Cox the revelations may hold the key to future health improvements for Māori and Pasifika populations.
The research is the first to sequence ancient DNA from 3,000-year-old skeletons to identify who were the first people to reach the Pacific Islands.
By examining skeletal remains from the first people to settle in Vanuatu and Tonga – the research was able to put a 40-year-debate to rest. They have shown that ancient settlers had little to no Papuan ancestry, which proved that the first people to reach remote Oceania were from Asian farming groups, with later movements bringing Papuan genes into the region.
Before this work, no ancient genomic DNA had ever been obtained from any tropical region, including the Pacific. This resulted in two opposing scenarios to explain why Māori and Pasifika have Papuan and Asian ancestry – the other stating that farming groups moving out of Asia mixed with Papuans near New Guinea and created a mixed group with both ancestries and the mixed group settling in the Pacific.
“This paper gives us the first basic picture of the genomic makeup of Pacific Islanders,” Professor Cox of the Institute of Fundamental Sciences says. “Unlike European New Zealanders, where we can leverage off research done in the UK and USA, we knew very little about the genomes of Pasifika and Māori. We knew that they had a mixture of both Asian and Papuan ancestry, but had no idea how this came about or when.
“Knowing this is important because some of the genetic variations caused by this population mixing will likely be linked to health outcomes, perhaps explaining why health issues like obesity and diabetes are such challenges for Pacific peoples today. Ultimately, understanding this DNA may give us new ideas for health treatments,” Professor Cox says.
“When you think about New Zealand, this was the last landmass in the Pacific to be settled, around 1,250 years ago. Most of this population mixing was already over by the time the first Māori arrived here, but the people in those boats were part of this great settlement process, and it therefore directly affects New Zealand Māori today.”
Skeletal remains
The study examined ancient DNA from three individuals who were among the earliest to settle in Vanuatu up to 3,100 years ago and one who was among the earliest to settle in Tonga up to 2,700 years ago.
The Vanuatu skeletal samples were extracted from a 3,000-year-old burial site, where 60 skeletons, whose skulls had been taken away by mourners, were discovered by construction workers on Éfaté Island in 2003. The Tongan skeletal samples were found at a site on Tongatapu Island (Talasiu site) these were the oldest securely dated skeletal assemblage from Polynesia around 2,500 years ago.
“Ancient DNA has radically reshaped our understanding of the human past in recent years, overturning models of European history and identifying substantial genetic mixing with archaic hominids, such as Neanderthals and Denisovans. However, ancient genomic DNA has only been reported from cold regions, like Europe and Siberia,” Professor Cox says.
The data was then compared to DNA samples from 356 present-day humans from 38 Southeast Asian and Oceanian populations.
Preparation of skeletal samples, DNA extraction and sequencing was carried out in dedicated ancient DNA laboratories at University College Dublin, Harvard Medical School, and the Max Planck Institute for the Science of Human History in Germany.
'Sex-biased' patterns
The study also reported the most accurate estimates of sex-biased admixture (the difference in the proportion of males and females contributing to a person genes) in diverse Southeast Asian and Pacific peoples to date.
“During the later stages of the settlement process, when the two groups were mixing, marriages between Asian women and Papuan men occurred very frequently, leading to unusual 'sex-biased' patterns of diversity in the genomes of their descendants.
“It is likely that this later mixing of people with Papuan ancestry was largely driven by Papuan men who came to Oceania and married resident Asian women,” Professor Cox says.
His previous research in modeling and developing theory about this sex-biased admixture process was an important basis for interpreting this finding.
The paper entitled Ancient genomics and the peopling of the Southwest Pacific was published in Nature today. Click here for the full report.
Caption: A 3,000-year-old burial in the Pacific Island nation of Vanuatu that is source of one of the ancient DNA samples.

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