DNA questions Pacific origins

By PATRICK GOWER and agencies

Polynesians may have migrated to the South Pacific through Southeast Asia and Indonesia, according to new scientific evidence.

Genetic research using male DNA has raised questions about previous studies that suggested Polynesian origins were in Taiwan or the southwestern Pacific islands of Melanesia.

The new study, from the University of Texas Health Science Centre in Houston, fails to support the older theory, suggesting instead the South Asian migration route.

University researchers studied male chromosomes from across the Pacific and Southeast Asia and found that Polynesian/Micronesian populations were far more closely related to Southeast Asians than Taiwanese.

"The divergence between the Taiwanese and the Polynesian/Micronesian populations is twice as great as the divergence of either population group from Southeast Asians."

Last night, Victoria University anthropology lecturer Dr Nancy Pollock said the new study meant existing theories would be revised.

"This means that everything doesn't fit as nicely as everyone's argued for the last 15 years," she said.

"It's all been very cosy so far, but maybe something else is happening.

"It's bringing science into explaining history, and that's always got some tricky parts."

Researchers studied the Y chromosomes of 551 men, comparing the distribution of 15 specific genetic markers.

The Y chromosome is passed from father to son.

Taiwanese aboriginal people carried markers that differed from those of either Polynesians of the eastern Pacific or Micronesians to the west.

The researchers felt the most likely explanation was that both the Taiwanese and Polynesians originated in Southeast Asia, but dispersed independently.

The researchers also noted that there has been controversy over the extent to which Melanesians contributed to the populations of Micronesia, to their north, and Polynesia.

They found that one marker common in Melanesians, H17, was missing in Polynesians, suggesting the Melanesian contribution was very low or negligible.

The research also deals a further blow to Norwegian explorer Thor Heyerdahl's theory that South Americans sailed to the South Pacific to become its first settlers.

Scientists also found no significant European contribution to Polynesian ancestry.

They said that while the Y chromosome study did not unequivocally point to a centre of origin for the Polynesians, the islands of Southeast Asia, such as the Indonesian group, emerged as a probable migration route.

The earlier theory of Polynesian origins, suggesting dispersal via Taiwan, had been based on studies of mitochondrial DNA.

That type of DNA is inherited only from the mother.

Some questions about the earlier studies have been raised in recent years, but the researchers said the reason for the different findings using the male-only Y chromosome was unclear.

One possibility might be differences in male and female migration patterns.