Julia Hinde reports from the annual American Association for the Advancement of Science meeting in Seattle

A piece of clay pottery from a site in China may provide evidence of the earliest domesticated maize in the Old World and add weight to theories of significant trade across the Pacific in the centuries prior to Columbus's American landings, geographers claim.

Carl Johannessen, emeritus professor of geography at the University of Oregon, told the AAAS meeting, that he is seeking funding to formally date the piece, which appears to have been moulded around an ear of the corn.

He hopes dating will show the object to be around 2,000 years old, pushing back the date of maize entry to the Old World from the Americas by more than 500 years.

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Professor Johannessen is also keen to carbon date a peanut excavated from what is thought to be a 4,000-year-old site in China.

Corn and peanuts are New World domesticates which do not grow wild in the Old World, and Professor Johannessen believes that their presence in Asia is proof of early sea routes between the continents. His work is funded by a Mormon foundation whose scriptures speak of movement across the sea from the Old World.

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Stephen Jett of the University of California in Davis explained that maize could not have crossed to Asia via the Bering Strait because it cannot be cultivated at this high latitude. He discounted its transfer via birds or ocean currents, saying that human involvement would still be needed to cultivate the crop.

Professor Jett hopes that DNA profiling in South America and Polynesia may help clear up uncertainties about early links between the peoples of the Pacific rim. "DNA evidence should be fairly definitive," he added.