DNA reveals new route of Pacific migration

By AAP with AG Staff 9 February 2011
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Polynesian people may have populated the Pacific via New Guinea rather than Taiwan as previously thought.

NEW DNA EVIDENCE has emerged which overturns theories on how humans spread across the Pacific.

The islands of Polynesia were first inhabited around 3,000 years ago, but where these people came from has long been a hot topic of debate amongst scientists. The most commonly accepted view, based on archaeological and linguistic evidence as well as genetic studies, is that Pacific islanders were the latter part of a migration south and eastwards from Taiwan which began around 4,000 years ago.

Now, scientists believe the DNA of current Polynesians can be traced back to migrants from the Asian mainland who had already settled in islands close to New Guinea 6,000 to 8,000 years ago. The evidence was uncovered by researchers at the University of Leeds in the UK, and published in the latest American Journal of Human Genetics.

“Our study of the [DNA] evidence shows the interactions between the islands of south-east Asia and the Pacific was far more complex than previous accounts tended to suggest and it paves the way for new theories of the spread of Austronesian languages,” says lead author, Professor Martin Richards.

Genetic signatures from mum provide record of inheritance

The type of DNA extracted and analysed in this kind of study is that in the cell’s mitochondria. Mitochondrial DNA (mtDNA) is passed down the maternal line, providing a record of inheritance which goes back thousands of years. The scientists look for genetic signatures which enable them to classify the DNA into different lineages and then use a ‘molecular clock’ to date when these lineages moved into different parts of the world.

“Most previous studies looked at a small piece of mtDNA, but for this research we studied 157 complete mitochondrial genomes in addition to smaller samples from over 4,750 people from across south-east Asia and Polynesia,” says Martin.

“We also reworked our dating techniques to significantly reduce the margin of error, he says. “This means we can be confident that the Polynesian population – at least on the female side – came from people who arrived in the Bismarck Archipelago of Papua New Guinea thousands of years before the supposed migration from Taiwan took place.”

However, many linguists maintain that the Polynesian languages are part of the Austronesian language family which originates in Taiwan. Martin and co-researcher Pedro Soares argue, though, that the linguistic and cultural connections are due to smaller migratory movements from Taiwan that did not leave any substantial genetic impact on the pre-existing population.