Wow, that completely changes my perception of history.

There are two competing theories on the initial population of the Americas. The first was a land bridge theory which suggests hunter-gatherers tracked mammoths across the once-frozen Bering Strait bridge of modern Russia/Alaska, but a newer and more popular theory is that Polynesian peoples arrived by boat navigation.

Apparently, sweet potatoes arrived in Polynesia around 1,200 and 1,300 AD, which gives a lot of credit to the idea that the first human inhabitants of the Americas arrived by boat from Polynesia.

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.