When thinking about the peopling of the Americas, there are the three aforementioned principal theories associated with the trans-Arctic Ice Age migrations that took place around 20,000 (as early as 25,000 and as recently as 10,000) years ago.

I describe it as the proto-Clausewitzian Beringian Land Bridge theory, the proto-Mahanian Fertile Shore, Kelp Highway or Coastal theory, and a more protracted, bi-directional SA国际影视传媒渟tandstillSA国际影视传媒� theory that postulates an extended (multi-millennia) human presence in Beringia, which remain unflooded for some 5,000 years, from which subsequent generations migrated bi-directionally forth to the Americas and back again into Eurasia.

There are numerous debates, and contending views on archaeological support for one or another, but knowing the diversity and ingenuity of our species it seems plausible to me that all three are correct to at least some degree, and not mutually exclusive of one another. In the case of how the Americas became peopled, all of the following may in fact be the most correct answer.

The original Beringian Land Bridge theory postulates the opening of an ice free passage enabling migration in search of megafauna (the Clovis spear hunters, who specialized in big game like mammoth, which went extinct around this time) some 13,500 years ago.  The Fertile Shore theory (also known as the Kelp Highway or Coastal theory), postulates a maritime migration along the fertile and life-sustaining Pacific coast.

Archaeological evidence indicates humanity arrived thousands of years before the ice free corridor opened up, but along much of this postulated route, sea level rise has erased any archaeological record. But not for all of their route, such as along coastal British Columbia, where there was a much smaller sea level rise of just two metres, preserving some of the archaeological record, and revealing increasing evidence of a maritime expansion, which is all the more plausible considering the Austronesian expansion across the Pacific a millennium ago crossed the open Pacific, a much riskier feet even if much later in the human story.
Beringia is the region stretching from the Lena River in Siberia to the Mackenzie River in Canada, along which I lived during the 1990s. It also includes the Yukon River watershed, which forms a riverine trade route from the Bering Sea all the way into Yukon and across its border into northern British Columbia, an active migration route from the late Pleistocene.

Interest in Beringia has grown in lockstep with the proliferation of theories on Beringian migration. On the Alaska side of Beringia, named the Seward Peninsula for William H. Seward, whose 1853 SA国际影视传媒淒estiny of AmericaSA国际影视传媒� speech presented AmericaSA国际影视传媒檚 polar ambitions as part and parcel of its rise as a global power, a vision that he achieved at least in part with the Alaska Purchase 14 years later.

And more than a century after, in 1978, then-U.S. president Jimmy Carter created a new national monument celebrating Beringian heritage called the Bering Land Bridge National Preserve on the Seward Peninsula, just across from Chukotka in Siberia, which two years later, as part of the sweeping Alaska National Interest Lands Conservation Act (ANILCA) that redressed the exclusion of subsistence protection from the Alaska Native Claims Settlement ACT (ANCSA) of 1971, it became a national preserve which opened these very lands to subsistence hunting by natives, linking, at least metaphorically, the original indigenous migration across Beringia to the restoration of indigenous subsistence to those very lands.

The shared heritage of the Beringian region, and the remembrance of the Ice Age interconnection of Siberia to Alaska via the land bridge, is the focus of a U.S. National Park Service research program that supports researchers on both sides of the bridge, helping to preserve its collaborative spirit in our own time, including geologist David Hopkins who conducted field research in the Seward Peninsula, and who worked with an interdisciplinary group of scholars to document the land bridge theory of migration across what is now the strait separating the United States and Russia.

The region, like adjacent parts of Alaska, has been experiencing profound effects of climate change, and over a decade ago, the Bering Land Bridge National Preserve experienced a sudden and massive die-off of an entire muskox herd from a storm surge that shattered sea ice, causing them to plunge into the icy depths, providing us with a bridge not only linking the two continents that nearly meet in Beringia, but the two extremes of Arctic climate that profoundly influenced humanity in the same region: the Ice Age land bridge that brought humanity to the Americas, and the current polar thaw, which appears to be fast bringing the last chapter of the Ice Age to its end in our time.