Wednesday, March 01, 2006

Pleistocene Voyages to North America

The recent meetings of the American Association for the Advancement of Science had two presented papers on the role of maritime voyaging in the Pleistocene colonization of the Americas. One by Dennis Stanford addresses the Atlantic side and another by Jon Erlandson addresses the Pacific. Let me start by saying that these aren't new theories, though the press releases might lead you to think so. Both Stanford and Erlandson have articles on this subject in this collection resulting from a 1999 symposium and James Dixon also explored Pacific maritime colonization in this book published in 1998. All have other articles on this in peer-reviewed publications and other venues.

I'll talk about Stanford first. It seems pretty certain that late Pleistocene humans at around 14,000 BP had the boat-building technology to enable them to do limited maritime voyages. Erlandson has a masterful run-down of the literature on this in the collection cited above. The most likely boat type is thought to be a kayak or umiaq-like skin boat similar to those used by the ethnographic Inuit. Stanford and his collaborator Bruce Bradley believe that it would have been possible for Pleistocene people to have crossed the Atlantic in boats during the 14,000 BP period, when we have the first confirmed human presence in the New World.

At that time, the polar ice cap extended far to the south of where it is today, and pack ice choked the North Atlantic. Stanford and Bradley theorize that the edge of the ice would have provided a "coastline" stretching from the Bay of Biscay to Labrador. People in boats could have traveled west along the edge of the ice, camping on ice-floes and subsisting on fish and sea mammals that they could hunt in route. Lost seal hunters could thus have found their way to North America.

When I first read this theory, one of my impressions was what an adventure story it sounded like. Obviously others felt the same as the BBC released a TV movie in 2002 based on the concept titled "Stone Age Columbus." I saw a replay of it on the Discovery Channel last fall and enjoyed it. The movie works hard to show details (taken from Inuit ethnographic analogy) of how a group of hunters in an umiaq would feed and warm themselves in those circumstances. Hostile encounters along the way with groups of outcasts from their own society are brought in as a plot device to heighten the drama.

Most of their argument rests upon what they see as the similarity in lithic technology between the Solutrean cultures known from France and the Clovis culture from North America. You can make a decent case for that. I think that the ice floe voyaging scenario isn't out of the question either. But I think that there are problems in the lack of DNA evidence to support it.

As I pointed out in an earlier post DNA evidence from Native Americans shows that their origins are in Central Asia. At the time of Stanford and Bradley's articles in the late 1990s, one of the five mitochondrial DNA haplogroups (designated "X") known from contemporary Native Americans had not been seen in Asia. This was seized upon as possible evidence of a prehistoric European migration. A subsequent paper in 2002 demonstrated evidence of haplogroup X populations in Asia as well as its presence in prehistoric Native American remains found in Washington state.

This would seem to close off that line of argument. Could Pleistocene emigrants from Europe have left an impact in terms of technology or culture and not leave a genetic "fingerprint"? I suppose it's possible. Think of a contemporary example: millions of people in India speak English and use European developed technology. Though the British Raj held sway there for 150 years or so, I would venture that the genetic impact of the British on the Indian subcontinent is minimal. Of course the British had writing and telecommunications (I'm going all the way back to semaphore and the telegraph here) that Pleistocene people didn't have to spread knowledge.

Early last month I saw a fascinating presentation by a DNA researcher named Brian Kemp at the monthly meeting of the Santa Barbara County Archaeological Society. Kemp is a very bright doctoral candidate in anthropology at University of California - Davis. He told us of his work studying mitochondrial DNA variation within Uto-Aztecan language speaking groups in central Mexico and the American Southwest. During prehistory in these areas, the axis of travel of change in technology (agriculture and ceramics) and language (though there is disagreement on this - nothing's ever easy) seems to be from south to north. In a nutshell (please lots of conditionals, if's and but's in there) Kemp's comparison of the genetic composition of the populations along this axis seem to indicate that technology and culture traveled but people didn't.

Another thing that Kemp's presentation showed (this is not a criticism of him!) is that DNA studies in support of archaeological and historical theorizing are still really in their beginning stages. Inadequate sample sizes of contemporary material and the loss of access to prehistoric samples due to NAGPRA re-burial are serious problems. I believe we are in for some big "swings" in conventional wisdom in this arena in the future.

So I will keep an open mind on Stanford and Bradley's theory - but it has issues.

The Pacific Rim voyage theory, as espoused by Erlandson and Dixon, relies on the same boat technology at the same time period, but seems to have more going for it. Voyagers could "coast" from Asia along the Beringian coast to North America without leaving sight of land. DNA evidence seems to support it. During the late Pleistocene sea levels were much lower than now, so archaeological sites along this coast are now under water. There is some evidence of these sites reported off the British Columbia coast, but much more work needs to be done to find these. Searches for drowned sites on Pleistocene coastlines in Florida by Michael Faught have yielded spectacular results. Similar work along the Pacific coast could pin this theory down.

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