Dr Andrea Manica, a geneticist from the University of Cambridge, said the finding had important implications for the population history of the Americas.

"I can't comment on how reliable the dating is (it is outside my expertise), but firm evidence of humans in North America 23,000 years ago is at odds with the genetics, which clearly shows a split of Native Americans from Asians approximately 15-16,000 years ago," he told BBC News.

"This would suggest that the initial colonists of the Americas were replaced when the ice corridor formed and another wave of colonists came in. We have no idea how that happened."

Thing is, if it was just displacement, there would still be mixing... hell, we mixed with Neanderthals, and others far more dissimilar than these populations would have been...

So, we have strong evidence (seems pretty irrefutable, but you would be the best judge of that here)of early human presence in North America, there have been assertions that stone tools were found in South America that are even older... all this indicates a large human presence in the Americas thousands of years before we previously assumed possible. Thousands of years before the migration events that seem to be confirmed by genetic analysis. Yet, as far as I know, genetic analysis hasn't even hinted at the existence of this population of early settlers.

Seems like we are forced to choose between:
1) Genetic analysis is flawed, or cannot for some reason pick up evidence of this earlier population.
2) The early population was wiped out prior to the later migrations
Or, and I have no idea if this could be reconciled with the genetic analysis,
3) perhaps there was a constant trickle of settlers making the journey...? This would maybe(?) prevent the NorthAmerican population from drifting too far from the Asian populations during the period where large scale migration events were not possible? Then when the bridge was clear the migration events that had been the previous theory happened and left their prints on the genetic record?

I certainly am not qualified in this area, but those would seem to be the only available options that would explain the evidence.