Genetic evidence suggests people got to the Americas about the same time as to Australia. That would have been by boat along Japan, the Aleutians, and down the west coast, maybe 50,000 years ago.

Polynesian came along tens of thousands of years later. They would have sailed across to Peru or Chile, and picked up sweet potato there. Surprisingly, not potatoes or peanuts, although they could have taken and then lost those.

We have certain evidence of hominins in California 130,000 years ago -- H. erectus, Neanderthal, Sap., or "other" -- although no evidence they left descendants.