CALGARY -- A commonly held belief about the route taken by the first humans to arrive in North America may be turned on its ear after an international study released this week.

It is thought that the migration of the first people into the Americas from Siberia occurred via the Bering Land Bridge through a corridor in what is now Western Canada. The area was opened up by the retreating ice sheets at the end of the last ice age between 14,000 and 15,000 years ago.

But a study -- "Postglacial viability and colonization in North America's ice-free corridor" -- published in the latest issue of Nature casts doubt on that theory.

"There was no vegetation, animal life or wood in the central parts of the corridor before 12,600 years ago," said the study's lead author, Eske Willerslev, from the Centre for GeoGenetics, Natural History Museum of Denmark at the University of Copenhagen.

Willerslev and his international crew, including a number of Canadian scientists, analyzed nine sediment cores from Charlie Lake and Spring Lake in British Columbia and Alberta -- the last areas of the corridor to thaw.

Their research, based on plant remains and environmental DNA, reveals the landscape couldn't support human life until about 2,000 years after the first humans were recorded in North America. Willerslev said there was no vegetation or animals, such as bison and mammoth, that were an important food source hunted by early Americans.

"It shows that the first humans to occupy the Americas south of the big ice sheets covering most of northern North America during the last ice age could not have come through the interior ice-free corridor, whether you believe these first humans were Clovis or earlier," Willerslev told The Canadian Press.

"It first became viable for travelling and survival around 12,600 years ago. You have archaeological sites in the U.S. and Chile that are at least some two thousand years older."

The Clovis were thought to be the first people to settle in North America around 13,500 years ago, at the end of the last ice age. But spearheads and DNA from a group predating the Clovis, were found at the Paisley Caves in Oregon and found to be as old as 14,000 years.

Willerslev now believes the most logical route that the early humans took was along the western edge of the North American continent including Alaska, British Columbia and Oregon. He said 14,000 years ago, most parts of North America would have been under ice with the exception of Alaska and the Yukon.

The next step in the research would be to explore the coastal route using the same technological approach, if possible, he said.

Willserslev said many in the scientific community he's spoken to are excited about the research but there are others unlikely to accept a different point of view.

"Some scientists will go to their graves with their original beliefs independent of the evidence. But that's all right," he said.

"What matters is what the majority view is. That sets the mindset of the next generation of researchers."