Perhaps they were here all along?
Native history makes no indication to the contrary.
DNA and bone studies suggest that there were more than one wave from Siberia. Even Europe and possibly Africa. Clearly ancient man followed the shore and glacier edge and probably even learned to sail on the open sea.
:’) The language development suggests a wide range of dates (from 35,000 years ago to present) for multiple waves of settlement, just like every other place on Earth. Fossil remains of hominids haven’t been found in the Americas, but literally no one is looking.