My North American Archaeology Professor postulated that the very first wave of humans coming over from Asia arrived some time around 32,000 years ago. Successive waves of settlement produced pressure to move south and East (not to mention true climate change as Ice Ages came and went).
The result is that those native to Southern South America look different from, say, Aztec descendants who look different from Seminole or Iroquois or Sioux or Innuit.
Then, about 1000 years ago, Europeans started coming in from the East, by water. Pre-Clovis sites were predicted, and have been found. (You don't find anything else if you quit digging because your dogma says that you are at the oldest layer with occupational debris/artifacts.)
He also noted that what seems like an attractive place to settle (because of location and resources), given a recurrence of favorable climate, will be attractive to people long after it was abandoned because climate or resources were not favorable.
Noteworthy are river confluences and areas near the ocean, but the latter were considerably moved around by sea level changes during glacial periods and much of the area which could have been settled is now underwater on the continental shelf, or beneath the North Sea and English Channel across the pond. Far more to speculate on than there is room for (or time) here, but neat stuff.
Science is never settled, because there is new data always coming in.
Dogma doesn't cut it.
