Unfortunately for the various hunter-gatherer bands that made their way to Beringia, though they could walk deep into what is today Alaska and parts of the Yukon, travel further east and south was blocked by a giant damn ice sheet that covered all of Canada. After all, though such things were starting to wane a bit, it was still the fucking ice age. As a result, these groups just kind of hanged out, traveling back and forth across the land mass, even returning to Siberia at times. Eventually these groups remained apart long enough to become genetically distinct from other nearby groups, becoming the Amarind people, the ancestors of most Native Americans, most closely related to groups which later became the Mongolian, Amur, Japanese, Korean, and Ainu populations.
As the Earth began to shift to a warmer climate, the great ice sheets began to recede, leaving behind a scoured landscape and resulting in the massive Missoula and Bonneville floods across the Pacific Northwest. As the ice sheets began to disappear, by 13,000 BCE it started to become possible to travel from Beringia down the British Columbia coast to what is today the United States. The earliest travelers on this route would have needed boats to get around many areas, but eventually a largely ice free corridor likely came into being. Drawn by plentiful food supplies, bands of Amarinds moved down this corridor, soon finding themselves in a land of plenty with a climate that didn’t involve freezing one’s balls off. Untouched by human hands, this new world had to have seemed like a paradise to these early pioneers.
What followed was a rapid migration into North and South America, with all parts of the new continent touched by human habitation by 10,000 BCE. The primary and initial route of migration was down the west coast with its rich food supplies, with groups eventually branching off eastward into the interior and onward to the Atlantic coast. The warming climate was playing havoc on the local biomes, causing erratic weather and large swings in the availability of food supplies. Most of the large wooly animals that had long sustained the Amarinds were going extinct, unable to adapt to the world changing around them. Not really wanting a similar fate, the Amarinds kept on the move, adapting their diets to eat anything they could find. This continued until around 6,000 BCE, when the climate finally stabilized into something fairly similar to the world of today.
With Mother Nature no longer acting completely insane, the various bands of Amarinds began to settle into distinct areas, adapting themselves to the specific biomes in which they found themselves and beginning to form distinct diets, cultures, and languages. In the area that is today the United States, these could be categorized broadly into the Northwest Coast, the California Valleys, the Columbia Plateau, the Southwest, the Plains, the Northeast, and the Southeast. Various bands staked out their claims, and from this point forward little gene flow took place between the major groupings, though within the groupings the bands interacted, both trading and fighting each other for resources. The Amarinds grew more numerous and split into hundreds of different unique tribes.
As the ice age came to a close, sea levels began to rise and Beringia began to sink under the Bering Sea, sundering the Old and New worlds once again. However, prior to this taking place, a second group crossed into Beringia and then into North America. The Na-Dene were a distinct group of people, both in their genetics and cultures, with a language quite different than the Amarinds. First entering North America around 8,000 BCE via the marshy remains of Beringia, they became the primary inhabitants of Alaska and Northwestern Canada, claiming some of the last lands to be uncovered by the retreating ice sheets and pushing out or breeding out the Amarinds still living in the area. Though largely remaining in the north, a few small groups did make it as far south as the northern Californian coast by 3,000 BCE. Thus established, they split into unique tribes that remained distinct from the earlier arriving Amarinds.
Though the former land bridge of Beringia was now underwater, a third distinct wave of migrants followed the Na-Dene. Around 3,000 BCE, the Aleut-Inuit people used boats to cross over from northwestern Siberia to Alaska. Too few to challenge the descendants of the Na-Dene and the Amarinds, they spread across the barren shores of the Arctic Ocean, carving themselves out a life in the harshest of conditions. Of all the early peoples who came to the Americas, they remained the most closely related to their Siberian predecessors.
