Peopling of the Americas

The timing and route by which humans first reached the Americas remain actively debated, but the most widely accepted evidence places the first arrivals south of the Ice Age ice sheets between roughly 15,000 and 20,000 years ago, with the oldest undisputed archaeological evidence, from the Swan Point site in Alaska, dated to about 14,000 years ago. During the Last Glacial Maximum, between roughly 26,000 and 19,000 years ago, lowered sea levels exposed Beringia, a wide land bridge connecting northeastern Siberia to Alaska, across which hunter-gatherer populations are thought to have crossed before dispersing southward through the continent. Two competing routes have been proposed for that southward dispersal: an interior corridor between the retreating Laurentide and Cordilleran ice sheets, which did not fully open until around 13,000 to 12,000 years ago, and an earlier coastal route down the Pacific shoreline, a theory supported by early sites such as Monte Verde in Chile, dated to about 14,500 years ago. Genetic studies indicate that Native American populations descend from an Ancient North Eurasian population that mixed with East Asian populations around 25,000 years ago, and this genetic and archaeological evidence has largely superseded the earlier Clovis First model, which had placed the first arrival at only around 13,000 years ago.