Did First Americans Arrive By Land and Sea?
for National Geographic News
|November 6, 2003|
A growing number of experts are radically rethinking how the Americas were first populated. Scientists say an emerging picture suggests that the earliest people to reach the New World may have arrived by both land and coastal routes.
For the last several decades, prevailing theory held that a small group of big game hunters in Siberia followed the Pleistocene megafaunamammoth, mastodon, and extinct bisonacross a land bridge that formed during the last Ice Age. Known as Beringia, it connected Asia to Alaska and northwestern Canada. As the glaciers began to retreat, an ice-free corridor opened up around 12,000 years ago, allowing people to make their way south to populate North and South America.
However, recent archaeological finds and geophysical studies have dramatically challenged this picture, advancing the possibility that people traveled both by boat and by foot.
"A variety of different lines of evidence have led to a wholesale reconsideration of the possibility of a coastal route," said Jon M. Erlandson, an anthropologist at the University of Oregon in Eugene.
Vance T. Holliday, an anthropologist and geoscientist at the University of Arizona in Tucson, said: "Recent findings have made it clearer that regional climate and geography played a much larger part in early migration patterns than previously thought, and increases the likelihood that people arrived using a coastal route."
Holliday organized the scientific panel that presented its findings at the annual conference of the Geological Society of America which concluded yesterday in Seattle, Washington.
"The change in emphasis from interior corridor to coastal route has been truly astonishing and only occurred in the last year or so," said Charlotte Beck, an anthropologist at Hamilton College in Clinton, New York. "This is really new for everybody."
The earliest reliably dated evidence of human habitation in North America are 11,500-year-old fluted projectile points found in Clovis, New Mexico. The distinctive points, which could be attached to a wooden spear to make a formidable weapon, became identified with small groups of people spreading slowly across North America who came to be known as the "Clovis" culture.
One of the first pieces of evidence to call the interior routethe so-called "Clovis first" theoryinto question was confirmation in 1997 of human habitation at a site known as Monte Verde in southern Chile. Artifacts left there by early peoples predate the earliest known Clovis artifacts by 1,000 years.
The find raised the question of how people could have reached South America without leaving a trace of their presence in North America. (Erlandson notes that "new evidence suggests that the ice-free corridor from Beringia does not appear to have been open early enough for it to have contributed to the 12,000 to 12,500 year old settlement of Monte Verde.")
Now, new, more precise geophysical data from geologists suggests there was a great deal of variation in regional climate and habitat across time in Beringia.
"The Bering corridor may have been open for much longer than previously thought," said Andrea K. Freeman, an archaeologist at the University of Calgary in Alberta, Canada. "It's possible the western end of Beringia was open as much as 30,000 years ago, while the regions bordering the Gulf of Alaska remained glaciated."
More telling has been a reappraisal of the southern coastline of Beringia.
For decades it was simply assumed that the coast of Beringia was an inhospitable place to live, said Erlandson. New evidence suggests that instead of a straight-line coast, the southern coastline of Beringia was comprised of hundreds of islands, shallow bays, and inlets. Such coastal topography would have facilitated coastal living and migration.
"This type of relatively complex coastline is much more conducive to human habitation," said Erlandson. "It provides more protected habitat. And it's much more productive, providing a wealth of resources for early settlers."
Similar shorelines around the Pacific Rim today frequently support large underwater kelp forests. Kelp forests provide habitat for sea mammals, shellfish, fish, and sea birds, providing a ready source of food. The forests also tend to break up waves heaving on shore, making for safer boating.
"The other thing that has occurred is a reappraisal of the maritime skills of early peoples," said Erlandson. "In the last several years, there has been a pretty dramatic shift about the role of the sea in human history."
Once humans moved out of Africa and into Asia and Europe, three waves of migration occurred: People traveled to Australia, Japan and the islands in western Melanesia, and to the Americas.
"We know that at least two of [these waves] occurred by boat," said Erlandson, noting that humans arrived in Australia by boat at least 50,000 years ago. "There's no reason to think the Americas couldn't have been colonized in the same way," he said.
Arguing for a Sea Route
Until now, one of the primary arguments against a coastal migration route has been the lack of archaeological evidence. "There are no sites," said Beck. "Of course, rising sea levels mean that most, if not all, of the sites would be underwater now."
Erlandson, who has written extensively on the importance of coastal habitats and the seafaring abilities of early humans, urges caution.
"We haven't proven it happened yet," he said. "There was no archaeological evidence supporting the interior route theory. It was really a leap of faith." He's also careful to add that "there's embarrassingly little data" to support arguments for a coastal route. "But that's what makes it interesting."
"The only thing that's certain is it has to be more complicated than just one group migrating across Beringia," said Beck. "It's more likely that there were numerous migrations at different times, by different routes."
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