Some talks at the AAAS meeting in St. Louis revive the discussion about the route taken by the first humans entering the Americas. These first peoples could have been big-game hunters following mammoth across the interior of the land bridge connecting Asia and North America, or they could have been fishers who followed the coasts. The coastal migration theory relies on the immense productivity of coastal kelp beds, and suggests that fishers could have made a very good living by just following the kelp highway.
The biggest difficulty with the coastal hypothesis has been the lack of archaeological evidence, presumably because the camps would be submerged as the ocean levels rose after thelast ice age. I have been able to see a few abstracts ( here and here ) suggesting that these data are slowly coming in.
It's not clear to me that these two routes are mutually exclusive. With that said, mtDNA from a tooth found in a coastal cave Alaska shows kinship with contemporary native americans throughout the New World, suggesting that at least the coastal people prospered.