I see this theory emerging on the peopling of America that seems to fit. Let me lay it on you in a few bold strokes :
During the height of the last ice age Homo Sapiens Sapiens/Cro Magnon, living in southern France and Spain – the Solutrean culture (http://en.wikipedia.org/wiki/Solutrean), explored and followed the southern edge of the then huge ice cap that covered half of the northern hemisphere. The Solutreans lived on the ice shelf, like the Inuit, for centuries. And only accidentally found America. So they WALKED to America. Across the ice. But not in a straight line. Why would they? They weren't aware of 'another side' to go to. So they couldn't have purposefully been going there. They simply lived on the ice, chasing walrus, seal and other high calory sea ice creatures (penguins?) and one day, about 15,000 years ago, made landfall at Nantucket.
So, maybe the Solutreans canooed or rafted a bit. But they probably walked 99% of the way. Across the ice.

Eventually, about 14,000 - 13,500 years ago*, they found themselves on a continent brimming with megafauna (http://en.wikipedia.org/wiki/Megafauna), and, with their highly effective hunting techniques (albeit extremely wasteful; http://www.jsonline.com/news/state/mar02/24849.asp), they lived in virtual paradise for a few thousand years, expanding their small numbers (but slowly: the hallmark of a well-to-do people) and exploring the continent. We now call them the Clovis people (http://en.wikipedia.org/wiki/Clovis_culture).
In the meantime, as the ice age came to an end, the ice cap retracted. And the ice bridge/connection between Europe and America was severed. There was no way back for the Solutreans/Clovis people. They were 'trapped' on the American continent. Not really a problem as they lived in virtual paradise anyway.
The same ice cap retraction that opened up the Atlantic also opened up the Bering land bridge. And ancient asians/proto-indians crossed it between 17,000–11,000 years ago in several waves and fanned out across America (http://en.wikipedia.org/wiki/Indigenous ... dge_Theory). Probably considerably more towards 11,000 years ago. http://en.wikipedia.org/wiki/Bering_land_bridge. Their numbers greatly outstripped the Solutrean descendants/Clovis people!
They met, of course.
So what happened when they did?
Well, it was a clash of 'civilisations'.
And clashes of civilisations are not renowned for their rosy outcomes, are they?
And the Clovis record abruptly stops 10,900 years ago. No younger sites, remains or artefacts have been found (yet). That is suspiciously close to the time the ancient asians/proto-indians' most massive waves into America took place.
Coincidence? Could be. But a connection seems more likely! When the proto-Indians appeared on the scene, the Clovis people vanished. Connect the dots and you get: the ancient asians/proto-indians caused the quick demise of the Solutrean descendants/Clovis people.
But why and/or how? Well, maybe they massacred them for their wealth! That's the simplest explanation. They could 'easily' do that as they were vastly superior in numbers (though inferior in development and 'civilisation').
Alternative explanations could also be possible, of course. For example, maybe the ancient asians/proto-indians simply introduced an infectious disease like a type of killer influenza or an archaic HIV/AIDS like strain that the Solutrean descendants/Clovis people succumbed to. And so on and so forth. The possible explanations are limited only by the stretch of the imagination, of course. In such cases it pays to go with the simplest: yes, it was a regular holocaust, the ancient asians/proto-indians massacred the Solutrean descendants/Clovis people: one human race exterminated another human race!
Then, the ancient asians/proto-indians continued to kill off the remainder of the megafauna with the hunting techniques they had copied from the Solutrean/Clovis people.
And the rest is history...
* the Clovis culture suddenly appears in the paleontological/archeological record 14,000 yrs ago, and disappeared from it just as suddenly, 10,900 yrs ago. No older or younger Clovis record has been found (yet). Why not? Simple: because there's nothing to find! They weren't there before 14,000 yrs ago! And they weren't there anymore after 10,900 yrs ago.
Most paleological finds seem to support this theory. Although the present day indians very much oppose it. Not really surprising.
In other words: imho, Clovis/Kennewick Man is a Caucasian! NOT an indian! (http://en.wikipedia.org/wiki/Kennewick_Man)
What do you think?
On a related note:
it is a sobering thought to have to face the ever increasing probability that holocausts are a fixed trait of the human condition . . .
RS