CORVALLIS, Ore. - As evidence mounts that the first inhabitants of the Americas arrived well before the once-popular "Clovis model" depicted, scientists hope to begin exploring raised marine terraces and other ancient landscapes in an effort to discover the oldest archaeological sites in the western hemisphere.

A forthcoming book, "Ice Age Peoples in North America: Environments, Origins, Adaptations," provides a synthesis of early new world archaeological discoveries. It also outlines some of the evidence that renders obsolete the Clovis theory, which had suggested that the Americas were populated through a single migration across the Bering Land Bridge some 11,500 years ago. The book will be published late this summer by the Oregon State University Press.

And this Oct. 28-31, scientists will present their newest theories and evidence at a major summit conference on First Americans studies. Called "Clovis and Beyond," the conference in Santa Fe, N.M., will be hosted by the Museum of New Mexico Laboratory of Anthropology. Conference organizers Rob Bonnichsen, OSU; Dennis Stanford, the Smithsonian Institution; D. Gentry Steele, Texas A&M University; and Kenneth Tankersley, Kent State University, have invited leading archaeologists, physical anthropologists and geneticists to presented illustrated lectures on state-of-the-art findings.

"The presentations will be in plain English, of interest to specialists in the field and the general public," said Bonnichsen, director of the Center for the Study of the First Americans at Oregon State. Panel discussions will look at the future of First Americans research and future public policy.

An increasing number of archaeological sites have been discovered that date back more than 12,000 years. Their locations, from the east coast of the United States, to the west coast of Chile, throw the entire picture of western hemisphere habitation into question.

"The old model that there was one migration, one culture, one people and one language that gave rise to all Amerindians today just isn't supported by archaeological, genetic and skeletal evidence," Bonnichsen said.

Perhaps the most fully researched, documented site in the Americas that pre-dates Clovis was found in Monte Verde, Chile. It was reliably dated at 12,500 years before present. Another excavation near that site may be as old as 31,000 years, though the research on that site is still in its infancy. Both excavations were conducted by University of Kentucky's Tom Dillehay.

Since the Clovis model has been proven invalid, no single model of habitation and migration has been widely accepted by scientists. In fact, there is little agreement on how long ago such habitation may have taken place.

What's missing, of course, is the "smoking gun" - a site that clearly demonstrates that humans inhabited the Americas thousands of years before Clovis. One possible reason, said Bonnichsen, has been the rising of sea levels since the demise of the last Ice Age.

"Sea levels rose by as much as 100 meters since the end of the Ice Age, so many coastal areas in which we would expect to find evidence have been destroyed," Bonnichsen said. "But there are some place that were active tectonically that actually have risen, and these ancient, raised marine terraces may provide some of the answers."

Such terraces have been found in southern Oregon, southern California and Baja, and are as old as 120,000 years. It is not inconceivable, Bonnichsen says, that humans may have been in the Americas that long ago.

"It would be naive to eliminate any of the major ideas now being discussed," Bonnichsen said. "Humans could have walked across the Bering Land Bridge before or after 11,500 years ago, as suggested by the Clovis First model. Alternatively, they could have come to the Americas by using small boats to move along the Pacific Rim, or possibly they could have come by use of small boats to move along the edge of lead ice when the North Atlantic froze over during the last ice age.

"Searching for the 'First Americans' is a bit like reconstructing a crime scene," he added. "You need to gather all of the evidence before deciding what happened. That evidence isn't always easy to discover. Older sites are often deeply buried and difficult to find.

"Frankly, archaeologists haven't always looked for sites that might go back 20,000 or 50,000, or 100,000 years because they didn't fit with the Clovis model."

The coastal environment may be a key because of the rich food source and the ability of people to travel by small craft. One theory is that the Americas were settled by humans who came from Asia in small boats, moving gradually toward the south over hundreds, and even thousands of years.

But other theories are also of interest, Bonnichsen said. By comparing skull measurements using sophisticated multivariate statistical techniques, physical anthropologists are developing new theories to explain the peopling of the Americas.

"We have a major breakthrough in this area," Bonnichsen said. "Clearly, human skull forms earlier than 8,000 years are distinctly different from later period skull forms. Some believe the differences indicate the presence of distinctly different populations, while others believe that these differences indicate the presence of one initial population that changed in the Americas.

This new "out-of-Europe" theory, and the Pacific Rim migration theory, may not be mutually exclusive.

No single model is likely to explain all of the similarities and differences of contemporary Native Americans, said Bonnichsen.

"What this really suggests is that we need to investigate all lines of evidence - archaeological, skeletal and genetic," Bonnichsen said. "If we can establish specific populations of people through time, it will begin to give us an idea of who inhabited the Americas, where they came from, and when."

Many of the latest theories and evidence about the peopling of the Americas will be unveiled at the "Clovis and Beyond" conference, which is aimed at the general public. A web site has been established on the conference at:

In addition to the nation's top experts on First Americans study, the conference will feature hands-on exhibits that will allow the news media and the public to examine Clovis artifacts, and explore current public policy relating to archaeological studies. Note to Journalists: Reporters interested in covering the October "Clovis and Beyond" conference, or in receiving more information on First Americans studies, may call Rob Bonnichsen at Oregon State University, 541-737-4596, or e-mail him at

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Rob Bonnichsen, 541-737-4596