DNA surprise in Pacific migration

By ANGELA GREGORY

An international genetics study has shown that the female voyaging ancestors of modern Polynesians attracted Melanesian islanders who joined the transpacific migration.

The surprising finding undermines the "express-train" theory, derived from archaeological, linguistic and molecular studies, that Austronesian peoples rapidly expanded into remote Oceania.

Study team member Dr Geoff Chambers, of Victoria University's Institute for Molecular Systematics, said the scientists had worked like molecular detectives to follow the trail of genetic evidence.

The researchers, led by scientists from Stanford University in California, tested DNA samples from 148 contributors of either Maori or Polynesian descent.

Dr Chambers said analysis of male-specific Y chromosome markers revealed a pattern of complex relationships between Pacific Island populations.

There were clear differences between the ways men and women had contributed to the Polynesian gene pool.

The findings indicated that men from Southeast Asia, Melanesia and New Guinea had been recruited into the voyaging populations.

"This is in marked contrast with female mitochondrial DNA markers which are more or less exclusively of the Southeast Asia type."

Dr Chambers said the results prompted a number of questions, but the new data helped to resolve some long-standing questions about how Polynesian settlement occurred.

"The whole story makes better sense now that we have evidence that genetic exchange occurred between the voyagers and resident populations they encountered along the way."

Dr Chambers said the research was prompted after his 1998 finding that Polynesians were closely related to the ancient hill tribe people of Taiwan, which had caused huge international interest.

He predicted there would again be worldwide academic interest in the latest study results, as the development of the Polynesian ethnic group was the last chapter in human evolution.