I believe it was Vine Deloria who stated somewhat unequivocally that there is no evidence that anyone ever came to North America via a Siberian landbridge. In other words, everything about that whole scenario is theory and there is no evidence of any crossing. Can anybody offer any evidence on that point? Most people seem to accept the proposition as confirmed fact because it has been repeated so many times.
I googled him up and he’s a academic gadfly and Native American historian that seems to revel in being a contrarian. Considering that his Bering Strait stuff is in a book titled “Red Earth, White Lies -Native Americans and the Myth of Scientific Fact- by Vine Deloria, Jr A compendium of Indian oral tradition and their challenge to science”. I think I’d take any geo-physical claims he’s making with a pickup truck sized grain of salt.
Having said that, here is some more on the issue. This site explains why the Bering Strait theory pisses some Native Americans off, and links to some excellent explanations of the theory.
Gadfly or not, I don’t find anything in the URL you provided to indicate any “evidence” supporting the landbridge “theory” so perhaps the gadfly is correct. Anybody else got anything?
I took a course on anthropology of North American Indians some years back. I don’t remember the books that we read, but the basic argument goes like this: if we investigate all the earliest archaeological sites we have from North America, a clear pattern emerges. Sites in the far north, in what is now Alaska and Yukon, date to about 13000 years back. Sites in the middle of North America date to no more than 12000 years back. Sites in what is now the American Southwest date to 11000 years back. Thus we have a clear pattern of movement from north to south.
The question then becomes, was it coastal migration or over the land bridge and then down through the continent. One important consideration is the ice age, which lasted until about 10000-11000 years ago. Thus, people were already moving southward across the continent during the ice age. For most of the ice age, there’s evidence that a complete barrier of ice would have blocked off the route south over land. However, recent research suggested a lull in the ice age around 13000 years ago. During this time, the coastal regions would have stayed frozen, but there would have been an unfrozen strip of land leading over the land bridge, through central Alaska, and down east of the Rockies to the central plains. Some researchers think that the earlier North Americans must have used this open unfrozen land, and that nobody would have traveled that far along the still-frozen coastline because there wouldn’t have been any food. Others disagree.
One book is Quest for the Origins of the First Americans, by James Dixon. It presents all sides in the debate and goes through a pretty precise and scientific explanation of the data being used.
Has there been any work with DNA to show genetic connections between American Indians and Siberian natives? You’d think that would nail it, PDQ.
DNA testing has been done.
Some newer evidence implies that an earlier (pre-Clovis) coastal migration took place that populated the Southwest and South America before the inland (Clovis) migration poplulated the rest of North America. And that the pre-Clovis populations had Autronesian roots rather than North Asian ones. I believe that it is thought that the pre-Clovis populations were pretty much wiped out by the later arrivals, or that they were absorbed into that population to some degree.
Some of the best evidence of pre-Clovis occupation comes from Monte Verde in Chile. (There are probably better cites than the one I’ve listed, if you spend some time googling.) Check out this map to see the 2 proposed migration sequences (you can click on the map for a larger image).
What exactly are you asking?
(1) Did the ancestors of Native Americans migrate from Asia to the Americas? = YES.
(2) Did they migrate through the Bering Strait region? = YES, but … there is also some highly disputed evidence of more southerly cross-Pacific migrations (i.e., directly east from Japan/Australasia/Polynesia, rather than north and back south).
(3) Did they migrate on foot? = MAYBE. This is the biggest and most legitimate point of contention: Did the people hike on foot via an actual exposed land bridge or on continuous icepack (glacier)? Or did they travel along the coast in boats? Either is possible (since humans have had seaworthy boats for at least 40-50,000 years, as evidenced by the Australian Aborigines).
There’s also that one ancient skeleton that was found up in Oregon or Washington. (Kennewick Man?) It has been determined that this guy was not of northern asian extraction, and in fact he most closely resembles the Ainu (the indigenous people of Japan).
It’s further evidence of pre-Native American habitation in the New World.
Yes, that’s the same thing I was speaking about. Kennewick Man was discovered in Washington State (Kennewick, WA). There have been other non-Mongoloid skeletons found in South America that pre-date Clovis.
I checked the reviews on amazon.com of Vine Deloria’s book, and the frequency of the comment “myth of evolution” does not inspire confidence in his scholarship. 
I have to take issue with that first cite that you presented. It claims that there is no controversy about the findings at the Monte Verde site, and that archaeologists have arrived at a consensus that it can be dated to 12,500 years back, before the Clovis Barrier. However, this just isn’t the case. There are experts in the field who still do not agree with that date, and insist that the evidence only supports dating it to 11,000 years back. It is still a major controversy, and the details of the various dating methods used and the questions that are raised about the evidence are incredibly complicated. At this point all we can say is that the question is still open.