DNA proof of when people entered the Americas?

When people came to the Americas (and how) has always been a huge puzzle to which we do not have (and may never have) all the pieces. The idea that the Clovis people came over the Bering land bridge 10-12,000 years ago has been largely set aside -they were important but they were not first. Pre-Clovis data are claimed in several places across both American Continents.  Evidence from the Pacific Northwest has pushed the arrival date back to at least 14,000 years, and sites like Monte Verde in Chile may come to be accepted as proven , which would not only raise the question of when but how.  Did people first come to the Americas via boat or raft, or did they come by land but sail down the coast, planting populations much further south than migration by foot could have done? "Dusty" Crawford of the Blackfeet tribe has, according to CRI Genetics, DNA which is unusually unmixed that is, his ancestors intermarried very little with other groups) shows that, through 55 generations, his ancestors arrived (and stayed) beginning 17,000 years ago.  The group he belongs to genetically  apparently originated in the U.S. Southwest, meaning his ancestors might have come down via the ocean in a pre-land bridge migration. The ocean migration theory is hard to prove because so much of what used to be the Pacific Coast has long since vanished under water, but everything we learn seems to point to a more complex series of events than a few groups walking over from Siberia.