The ancestors of today's Polynesians and Micronesians were probably East Asians who quickly island-hopped through Near Oceania—what is now Australia, New Guinea, and the Solomon Islands—a new genetic study suggests. Jonathan Friedlaender and colleagues found that the two modern-day groups show little genetic relation to the indigenous peoples of Near Oceania. The finding supports theories that Polynesians instead descended from East Asians and aboriginal Taiwanese who apparently raced through the region.
     "They left very few genes behind," said Friedlaender, a professor emeritus of anthropology at Temple University in Philadelphia, Pennsylvania. "And they incorporated very few genes from the people in this region of Near Oceania, [although] they stayed for three or four hundred years before moving on to explore the central Pacific islands, where they became Polynesians and Micronesians," added Friedlaender.
     The study also reveals that Melanesian peoples (those from Vanuatu, the Solomon Islands, Papua New Guinea, and Fiji) harbor incredible genetic diversity—evidence of tens of thousands of years of relative isolation and a series of small migrations from Asia. "There's more population divergence in these islands than you see across all of Europe," Friedlaender said. "You can really tell by the way people look, and now genetically, what island they are from." Archaeologist Patrick Kirch said, "It's what you'd expect over a long time period like that. You see the same complexity in languages. New Guinea alone has something like 900 languages in its interior. That's probably the highest density of language differential per square mile in the world," said Kirch, of the University of California, Berkeley.
     Experts have spent decades pondering how humans settled the Pacific islands. Commonly held theories suggest that Near Oceania was colonized first, between about 30,000 and 50,000 years ago. The newcomers arrived in small numbers. In succeeding centuries their populations became isolated in a way that few people have anywhere in the world. But between 3,000 and 3,500 years ago, a new migration occurred, featuring an influx of peoples from Asia called the Lapita — the ancestors of those who would go on populate distant Polynesia and Micronesia.
     Previous studies suggested that the Lapita's most likely origin was Taiwan and East Asia—but opinions diverge concerning the history of these people. Friedlaender's study supports an 'express train' theory — the idea that they plied the waters in outrigger vessels and inhabited offshore islands and coastal areas not heavily populated with indigenous Melanesians. Some scientists, however, hold firm to the 'slow boat' theory — the idea that Polynesians had Melanesian ancestors on their family tree.
     Some interaction between the Lapita and Melanesian peoples is evident, but the critical question for scientists is the extent of this commingling. Geneticist Spencer Wells, a National Geographic Society explorer-in-residence and director of the society's Genographic Project, thinks that the genetic data may show that Polynesians and Micronesians are a mix of Taiwanese aborigines, East Asians, and Melanesians. He pointed out that the mitochondrial DNA evidence—which is passed down from females—tends to support the express-train theory. But the Y-chromosome, or male, evidence supports a slow-boat process, he said. This "suggests something interesting is going on, perhaps with different male and female migration patterns, which we see in other regions of the world," he said.

Source: National Geographic News (17 January 2008)