Chicken of the sea: poultry may have reached Americas via Polynesia.

Thor Heyerdahl got it backwards. More than 40 years ago, the late explorer proposed that the Inca or their predecessors voyaged from South America to Polynesia by raft. On the contrary, a new study indicates that Polynesian seafarers reached what's now Chile by about 620 years ago. That conclusion hinges on the first evidence of when chickens arrived in the Americas.

A team led by anthropologist Alice A. Storey of the University of Auckland in New Zealand used radiocarbon dating and a comparison of ancient DNA to determine a Polynesian origin for a chicken bone previously unearthed at Chile's E1 Arenal site. Mitochondrial DNA extracted from the El Arenal bone contains an exact copy of a genetic sequence that appears in comparable DNA from 600-to-2,000year-old chicken bones found in Tonga and American Samoa. Those islands lie 6,000 miles west of Chile.

Europeans arrived in South America around 500 years ago, after the Inca had incorporated chickens into religious ceremonies, according to Storeys group.

Storey and her coworkers performed radiocarbon dating on one El Arenal chicken bone selected from 50 bones recovered in 2002. The researchers then isolated a particular segment of mitochondrial DNA from the same bone and from 11 chicken bones found at pre-European archaeological sites in Polynesia. They found the same sequence in all the bones.

This stretch of DNA undergoes frequent alterations over generations. Yet the researchers found the same DNA segment in feathers of two living chickens belonging to a blue-egg-laying breed in Chile. Selective breeding may by chance have preserved the Polynesian sequence, the researchers suggest. The new findings will appear in the Proceedings of the National Academy of Sciences.

"The weight of scientific evidence is now squarely behind the hypothesis that it was seafaring eolynesians who sailed from the islands to South America and returned" remarks archaeologist Patrick V. Kirch of the University of California, Berkeley.

In 1989, Kirch reported that preserved sweet potatoes up to 1,000 years old, found at Polynesian archaeological sites, had originated in South America. The new evidence supports a scenario of long-distance canoe voyages by Polynesians, Kirch says.

Archaeologist Betty Meggers of the Smithsonian Institution's National Museum of Natural History in Washington, D.C., disagrees. In her view, both a black-boned breed of chickens now found in Central America and the blue-egg variety in South America originated in Asia.

Pre-Columbian transfers of various plants, animals, and cultural traits occurred in both directions from Asia to South America, Meggers holds. The most likely sea route ran north of Hawaii and down America's Pacific coast, she says.

Moreover, the claim that the Inca possessed chickens "is historical fiction," asserts archaeologist Michael E. Moseley of the University of Florida in Gainesville. No chicken remains have been found at Inca sites, although the Spanish sometimes referred to a native duck breed as "chickens" he says.

Further work must be done to confirm the age of the El Arenal chicken bones and to establish that Polynesians regularly visited South America, Mosdey adds.