From rats  to bacteria , researchers have traced the spread of all sorts of critters to figure out when the first intrepid humans reached the islands of Polynesia, one of the last places on Earth to be settled by people . Next up: coral. Archaeologists are dating tools made of coral to pinpoint precisely when humans occupied the oldest known archaeological site in remote Oceania—Nukuleka, on the island of Tongatapu in the island Kingdom of Tonga. At Nukuleka in the past, archaeologists have relied on radiocarbon dates of wood associated with distinctive Lapita earthenware pottery: the red, stamped ceramics left behind by the first seafarers, who swept out of Southeast Asia and into Polynesia. But these dates haven't been particularly reliable. Now, archaeologist David Burley from Simon Fraser University, Burnaby, in Canada and two Australian colleagues have dated coral files that the early settlers used to smooth and sculpt the surfaces of wood and shell artifacts. Using uranium-thorium dating on the coral, they found that the files were made between 2830 and 2846 years ago —a remarkably precise 16-year window—the researchers report today in PLOS ONE. Because these early settlers left a trail of coral files throughout Oceania, this new method "provides significant new opportunities for our understanding of the exploration and settlement of the far distant islands spread across the South Pacific," Burley says.
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