New radiocarbon dating of fossils suggests

(CNN) -- Archaeologists say a site in South Carolina may rewrite the history of how the Americas were settled by pushing back the date of human settlement thousands of years.But their interpretation is already igniting controversy among scientists.An archaeologist from the University of South Carolina on Wednesday announced radiocarbon tests that dated the first human settlement in North America to 50,000 years ago -- at least 25,000 years before other known human sites on the continent."Topper is the oldest radiocarbon dated site in North America," said Albert Goodyear of the University of South Carolina Institute of Archaeology and Anthropology.If true, the find represents a revelation for scientists studying how humans migrated to the Americas.Many scientists thought humans first ventured into the New World across a land bridge from present-day Russia into Alaska about 13,000 years ago.This new discovery suggests humans may have crossed the land bridge into the Americas much earlier -- possibly during an ice age -- and rapidly colonized the two continents."It poses some real problems trying to explain how you have people (arriving) in Central Asia almost at the same time as people in the Eastern United States," said Theodore Schurr, anthropology professor at the University of Pennsylvania and a curator at the school's museum."You almost have to hope for instantaneous expansion ...

But whether the Topper site proves valid, Collins said most archeologists now believe people settled in America before 13,000 years ago, refuting a theory that has held sway for 75 years.Since the 1930s, archaeologists generally believed North America was settled by hunters following large game over the land bridge about 13,000 years ago."That had been repeated so many times in textbooks and lectures it became part of the common lore," said Dennis Stanford, curator of archeology at the Smithsonian Institution."People forgot it was only an unproven hypothesis."A growing body of evidence has prompted scientists to challenge that assumption.A scattering of sites from South America to Oklahoma have found evidence of a human presence before 13,000 years ago -- or the first Clovis sites -- since the discovery of human artifacts in a cave near Clovis, New Mexico, in 1936.These discoveries are leading archaeologists to support alternative theories -- such as settlement by sea -- for the Americas.

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