Fast train to New Zealand

A new analysis of genetic diversity in Pacific Islanders backs up the 'fast train hypothesis', which holds that Polynesian and Micronesian peoples moved quickly through the Melanesian islands during their diaspora 3000 years ago and have little in common genetically with Melanesian people.

A genome scan of autosomal markers - 687 microsatellites and 203 indels - from almost 1000 individuals showed that Polynesians and Micronesians show strong genetic relation to East Asians, particularly Taiwanese Aborigines, and have little genetic similarities with Melanesian peoples.

The study, The Genetic Structure of Pacific Islanders', was published online by PLoS Genetics.

Lead author Jonathan Friedlaender, a professor of anthropology at Temple University in the US, said the new analysis was consistent with the fast train hypothesis.

"Our genetic analysis establishes that the Polynesians' and Micronesians' closest relationships are to Taiwan Aborigines and East Asians," Friedlaender said.

The analysis backs up previous studies using mitochondrial DNA that the ancestors of Polynesians and Micronesians originated in Taiwan, moved through Indonesia to Melanesia and then dispersed through the outer islands of Oceania and New Zealand.

The study also showed that differentiation between Melanesian people is quite high, varying not only between islands but by island size and topography, with the genetic pattern loosely mirroring different language groups.

"The first settlers of Australia, New Guinea, and the large islands just to the east arrived between 50,000 and 30,000 years ago, when Neanderthals still roamed Europe," Friedlaender said.

"These small groups were isolated and became extremely diverse during the following tens of thousands of years.

"Then, a little more than 3000 years ago, the ancestors of the Polynesians and Micronesians, with their excellent sailing outrigger canoes, appeared in the islands of Melanesia, and during the following centuries settled the islands in the vast unknown regions of the central and eastern Pacific."

The study sample concentrated on Papuan-speaking populations and their neighbours in the Bismarck and Solomon Islands; the island of Belau in Micronesia; Samoans and Maori; and aboriginal people from Taiwan.

It found that while Polynesian people are genetically distinctive in their own right, they have much more in common with Micronesians, Taiwanese Aborigines and East Asians than with Melanesians.

"Some groups in Island Melanesia who speak languages related to Polynesian, called Austronesian or Oceanic languages, do show a small Polynesian genetic contribution, but it is very minor - never more than 20 per cent," Friedlaender said.

"There clearly was a lot of cultural and language influence that occurred, but the amount of genetic exchange between the groups along the way was remarkably low.

"From the genetic perspective, if the ancestral train from the Taiwan vicinity to Polynesia wasn't an express, very few passengers climbed aboard or got off along the way."

The study also involved researchers from New Zealand's Victoria University, the Papua New Guinea Institute for Medical Research, the Mackay Memorial Hospital in Taiwan and the universities of Maryland, Yale and Binghamton in the US.