Rat DNA Offers Clues to Pacific Colonization, Study Says

John Pickrell
for National Geographic News
June 9, 2004

Wherever people go, rats go too. Now researchers are making use of this fact to help understand patterns of human migration. A new genetic comparison of rats from various Pacific islands presents clues about the origins of Polynesian people.

The study, published this week in the science journal Proceedings of the National Academy of Sciences, strikes a blow against one popular theory of how remote Pacific islands were colonized, and argues that the migration was a slow and complex process.

"People in the Near Oceania region of the Pacific have a long history of interaction with other groups," said study author Elizabeth Matisoo-Smith, a biological anthropologist at the University of Auckland, New Zealand. "[This] make[s] understanding the prehistory of the region difficult using human genes alone."

Noting that Polynesians and their ancestors carried plants and animals as they migrated, Matisoo-Smith said, "We can use the genetic variation in those species to track the movement of the people who carried them."

The technique is similar to one used by archaeologists to uncover clues about early peoples by pinpointing the origins of stone or clay used in ancient tools and pots, Matisoo-Smith said.

Epic Journey

Pacific settlement is thought to have begun around 40,000 years ago with the migration of people from Asia into New Guinea and Australia. By 30,000 years ago, these early people had sailed onto the Solomon Islands and the Bismarck Archipelago, a region known as Near Oceania.

Colonization of so-called Remote Oceania—the region east of the Solomon Islands that encompasses Vanuatu, Fiji, Tonga, Samoa, and far beyond—did not begin until much later. Precisely how this transpired has been the subject of vigorous debate for centuries.

One popular theory is known as the "express train" model. It argues that the Lapita people, who first populated Remote Oceania, represent a second wave of colonists who rapidly swept their way from Taiwan through Southeast Asia and Near Oceania and out into Remote Oceania. According to the theory, the process, which started 3,500 years ago, took just a few centuries to complete.

Advocates believe that the Lapita are the ancestors of the Polynesians and that they had little or no mixing with existing populations in Near Oceania. Evidence for the theory comes from striking similarities between languages spoken by indigenous inhabitants of Taiwan and Pacific Islanders.

But other theories suggest different scenarios. One holds that the Lapita people were made up of existing Near Oceania inhabitants alone, with little input from Taiwan. Another argues that the Lapita descended from people who did come from Asia, but underwent plenty of mixing with people in New Guinea, the Solomon Islands, and other parts of Near Oceania as they migrated.

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