A publication of the Archaeological Institute of America
New genetic data are calling into question long-accepted views about the origins of Polynesians, the inhabitants of the scattered central and eastern Pacific islands. After colonization of the Indonesian islands, Australia, and New Guinea by 40,000 years ago, the Solomon Islands southeast of New Guinea apparently formed the eastern limit of human habitation in the South Pacific. Three thousand years ago, however, colonization of islands farther east began. These later colonists were believed to have originated in mainland Asia, perhaps southern China, voyaging through the corridor of inhabited islands on their way east.
In a recent issue of the American Journal of Human Genetics, Oxford University's Martin Richards and his colleagues reviewed the geographic distribution of a set of shared genetic traits called the Polynesian motif. Many scholars have viewed the genetic uniformity of Polynesians as strong support for what is informally known as the express train model of rapid expansion out of a homeland in Taiwan or southern China around 6,000 years ago with little mixing between them and existing populations in Melanesia and Micronesia. Richards and his colleagues, however, found that the genetic evidence indicates the Polynesians came from somewhere in the voyaging corridor--perhaps eastern Indonesia between southeastern Borneo and the Moluccas. Furthermore, the Polynesian motif has not so far been found anywhere in China, Taiwan, or the Philippines, and it is thought to date back in eastern Indonesia something like 17,000 years. These findings contradict the timing and geography of the express-train model for Polynesian origins.
Genetic evidence used to support the express train concept was recently published in the journal Nature by evolutionary biologist Christopher Austin of the South Australian Museum. Austin examined the DNA of a small Pacific island lizard (Lipinia noctua) and found that on islands west of the Solomons it was genetically diverse but on Polynesian islands it was more uniform. Austin believes a few lizards (or even a single pregnant female) could have stowed away on a canoe in New Guinea or a nearby island. Their progeny evidently then moved from island to island farther east into the Pacific as uninvited hitchhikers on voyaging canoes. Because this founding population was small, it had a restricted gene pool and therefore less genetic diversity. This, Austin claims, is evidence that Polynesians swept rapidly out of Asia.
Many Pacific archaeologists are challenging this conclusion. As anthropologist Kevin Kelly of the University of Iowa notes, the lizard genetic evidence only deals with the unintentional human transport of this small creature from somewhere in the New Guinea area to Polynesia, not from Taiwan or southern China (where the lizard, in fact, does not exist). In short, the lizard genes tell us nothing about an ancient Polynesian homeland in Asia, or about how fast they moved to the central and eastern Pacific islands beginning 3,000 years ago.