When I first began studying archaeology and anthropology, the ‘experts’ stated that humans arrived in North America about 10,000 years ago. I just smiled and did not argue with the liberal creepozoid ‘teacher.’ Just because we did not have concrete evidence did not mean we could not use common sense. It was obvious to me that humans populated North America much earlier, and we just had to find the evidence. The surface of the planet hides, changes, and destroys stuff every day. Patience will reveal much eventually.
In addition, what is known now includes the fact that Flores Island had human residents at least 800,000 years ago, when the island was already separated from the mainland, meaning, the people got there by watercraft. The Americas are no different than any other nook and cranny of the Earth, settled and resettled by continual migrations.