The Americas were first settled by Stone Age Europeans who crossed the Atlantic by boat during the last Ice Age up to 20,000 years ago, a new book has claimed.
The scientists behind the claim say people known as the Solutreans, living in France and northern Spain, followed the coast of an ice shelf stretching south into the ocean from the Arctic to reach the continent.
They believe they then settled in an area stretching from the eastern United States to Venezuela, while the continent was further settled by early people crossing a land bridge linking Asia with Alaska across what is now the Bering Sea.
Across Atlantic Ice, by archaeologists Professor Bruce Bradley of the University of Exeter and Dr Dennis Stanford of the Smithsonian Institution in Washington DC, is based on more than a decade's research into the origins of the Clovis culture.
The Clovis are thought to be behind 12,000-year-old Stone Age tools found in New Mexico 80 years ago and the scientists claim these people were the descendants of Solutreans who had arrived after making a long journey by boat along the edge of the ice.
Professor Bradley said: "We now have really solid evidence that people came from Europe to the New World around 20,000 years ago. Our findings represent a paradigm shift in the way we think about America's early history. We are challenging a very deep-seated belief in how the New World was populated. The story is more intriguing and more complicated than we ever have imagined."
The book, launched at the National Museum of Natural History at the Smithsonian, claims that the continent was settled from east and west, but that the people arriving from Europe could predate those coming across from what is now Russia into Alaska by up to 5,000 years.
They say that discoveries on the eastern seaboard of the United States show that Europeans arrived "no later than 18,450 years ago and possibly as early as 23,000 years ago, probably in boats from Europe".
They also claim these early inhabitants made stone tools that differ in significant ways from the earliest stone tools known in Alaska. But they admit they are so far unable to clearly identify how these Europeans are linked to contemporary Native American peoples.
Dr Stanford added: "This book is the result of more than a decade's work, but it is just the beginning of our journey."