Washington: University of Leeds researchers have found new evidence that may overturn the current theories of how humans colonised 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 that began around 4,000 years ago.
But the Leeds research has found that the link to Taiwan does not stand up to scrutiny. In fact, 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 some 6-8,000 years ago.
The type of DNA extracted and analysed in this kind of study is that stored 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 that 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.
Lead researcher, Martin Richards, explained, "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 Southeast Asia and Polynesia."
Nevertheless, most linguists maintain that the Polynesian languages are part of the Austronesian language family, which originates in Taiwan. And most archaeologists see evidence for a Southeast Asian influence on the appearance of the Lapita culture in the Bismarck Archipelago around 3,500 years ago.
Richards and co-researcher Pedro Soares have argued 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.
"Although our results throw out the likelihood of any maternal ancestry in Taiwan for the Polynesians, they don`t preclude the possibility of a Taiwanese linguistic or cultural influence on the Bismarck Archipelago at that time," explained Richards.
"In fact, some minor mitochondrial lineages back up this idea. It seems likely there was a ``voyaging corridor`` between the islands of Southeast Asia and the Bismarck Archipelago carrying maritime traders who brought their language and artefacts and perhaps helped to create the impetus for the migration into the Pacific," he added.
The findings have been published in The American Journal of Human Genetics.