Sail away: tools reveal extent of ancient Polynesian trips.

The ocean wasn't enough to hold back the daring seafarers who settled the islands of East Polynesia beginning around 4,000 years ago. A new analysis of stone tools underscores the nautical skill of ancient Polynesian mariners. It indicates that, about 1,000 years ago and prior to European contact, these intrepid canoeists transported rocks for toolmaking from Hawaii to islands more than 4,000 kilometers to the south.

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Legends recounted by Polynesian islanders refer to ancestors in the distant past who used canoes with sails to travel south from the Hawaiian Islands to Tahiti and then east to the Tuamotu Islands. Chemical studies of stone tools previously recovered in the Tuamotu Islands back up those local accounts, say geologist Kenneth D. Collerson and archaeologist Marshall I. Weisler of the University of Queensland in St. Lucia, Australia.

The Tuamotus and the nearby Society Islands "could be approached from all quarters and were thus probably important in Polynesian trade," Collerson and Weisler conclude in the Sept. 28 Science.

The scientists assayed a variety of trace elements and isotopes in 19 basalt adzes--woodcutting implements resembling hoes, with stone blades fastened to the ends of wooden shafts. The late Polynesian archaeologist Kenneth Emory found the artifacts on nine coral atolls in the Tuamotus between 1929 and 1934.

Collerson and Weisler also characterized 28 volcanic-rock sources throughout Polynesia by their trace elements and isotopic compositions.

Comparisons of the Tuamotu adzes with these rocks showed that all but one came from surrounding island groups, such as the Marquesas, Pitcairn, Austral, and Society Islands.

The chemical signature of the final adze places its origin in Hawaii. The likely sea route between Hawaii and Tahiti, one of the Society Islands, via the Tuamotus has favorable winds and currents for roundtrip sea voyages, the researchers say.

Archaeologist Ben Finney of the University of Hawaii in Honolulu agrees. In 1976, he demonstrated that people could have settled Polynesia by navigating canoes across thousands of kilometers of open sea. He and his colleagues built a 19-meter-long reconstruction of an early two-masted Polynesian voyaging canoe. Taking roughly 2 months, they sailed the craft from Hawaii to Tahiti and back, passing through the Tuamotus along the way.

Ancient canoe voyagers must have passed their knowledge from one generation to the next until around 550 years ago, when most open-sea journeys ceased in East Polynesia, the Australian researchers suggest.

The new findings follow a report that Polynesian seafarers reached what's now Chile by about 620 years ago (SN: 6/9/07, p. 356). A bone from a Chilean archaeological site contains an exact copy of a genetic sequence that appears in DNA from 600- to 2,000-year-old chicken bones found in Tonga and American Samoa.

That evidence "provided archaeological support for Polynesians having reached South America in pre-Columbian times," Finney says. "Now we need to look for Polynesian basalt adzes there."