What theories about how the first Americans arrived?

Much of this new theorizing is driven not by archaeologists wielding shovels but by evolutionary geneticists taking DNA samples from some of the oldest human remains in the Americas, and from even older ones in Asia. Those discoveries have opened a wide gap between what the genetics seem to be saying and what the archaeology actually shows. Humans may have been on both sides of the Bering Land Bridge some 20,000 years ago. But skeptical archaeologists say they will not believe in this grand idea until they hold the relevant artifacts in their hands, pointing out that no confirmed North American archaeological sites older than 15,000 to 16,000 years currently exist. But other archaeologists are confident it is only a matter of time until older sites are discovered in the sprawling, sparsely populated lands of eastern Siberia, Alaska and northwestern Canada.

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