It is worth pausing to appreciate the geographic scale of what the founding of the Americas ultimately produced.

From the moment the founding population crossed from Beringia into the Americas — whether one founding event or several, whether along coastal routes or through interior corridors — human beings began adapting to an extraordinary range of environments.

The Americas span from the Arctic tundra of Alaska and northern Canada to the tropical rainforests of the Amazon basin, from the high-altitude plateaus of the Andes to the temperate forests of the Pacific Northwest, from the deserts of the Southwest to the grasslands of the Great Plains, from the subarctic forests of Canada to the maritime southern tip of South America.

In each of these environments, the founding population and its descendants developed specific adaptations — physical, technological, and cultural — suited to the local conditions.