First Americans Siberia to the Great Plains Beringia Land Bridge Last Glacial Maximum

The following presentation covers some of the earliest known archaeological sites in North America that occur before and during the last glacial maximum period. We are looking at the Bering Sea at the center of this map. Asia is on the left side of the Bering Sea and North America is on the right side of the Bering Sea. We are going to go back in time. At 20,000 years ago, we are at the last glacial maximum. Ice covers modern Canada and the northern United States. Because so much water is locked up in the ice, the sea levels are much lower. Two relevant terms require some clarification. The first term is last glacial maximum. The last glacial maximum refers to the height of the last glacial period about 20,000 years ago. The landscape you see here. You can think of the glaciers as a slow tide and they wax to a high tide at about 20,000 years ago, reaching their maximum extent, and then they wane back like a receding tide to their current position today. Pleistocene is another term that requires explanation. The Pleistocene is the geologic epoch in which prehistoric humans emerged. The Pleistocene epoch is hallmarked by the presence of large ice masses that began about 2.7 million years ago and continued until about 10,000 years ago. We used to call the Pleistocene the Ice Age, but now we realize that the last 2.7 million years are a series of high glacial periods and interglacial periods. We are living in an interglacial period now. If you go back to the last glacial maximum period 20,000 years ago, we have a vastly different landscape. The glaciers cover almost all of Canada. The Yukon here is a portion of Canada that is ice free, adjoined to modern Alaska here. About 20,000 years ago, the sea levels are so low that North America and Asia are connected. The land mass connecting North America and Asia during the Pleistocene is an area known as Beringia. Beringia is often called the land bridge. From this satellite reconstruction, we can see that North America and Asia are connected by a fairly large land mass, Beringia, and this is sometimes different than what we think of whenever we think of the term land bridge. Let's start in Siberia on the Asian side of the land bridge. An important archaeological site in Siberia, the Yana RHS site, has a radiocarbon date to 27,000 years ago. Some of the following dates are controversial among archaeologists because they have overturned previous models of human migration and occupation. Thus, I have provided a peer-reviewed reference for the site here. This Yana RHS site is relevant to ancient North America for at least three reasons. First, Siberia is connected to North America during the last glacial period, meaning that the culture in Siberia has an immediate geographic connection to the first Americans. Second, the site is above the Arctic Circle, showing that human populations, even during the last glacial period, could live in harsh extreme northern latitudes similar to those found in Alaska and the Yukon. Third, we have proof that humans are living at the latitude of Alaska and the Yukon this deep in the Pleistocene. For context, the Yana RHS site at 27,000 years old is old enough that Neanderthal populations are still in existence in the Mediterranean world. The Yana culture of Siberia or a similar people may have extended from Siberia into Alaska at this time. The Bluefish Cave site in modern Yukon territory supports this early migration. At Bluefish Caves, cut marks on animal bones have been dated back to 24,000 years ago, nearly contemporary with the Yana RHS site in Siberia. The Yukon provides even more Pleistocene sites. While Bluefish Caves is consistent with Siberian sites from the same time, the Yukon has other sites with even older dates. Mammoth bone fractures, consistent with human usage from near Dawson Yukon and Old Crow Yukon, returned radiocarbon dates from 40,000 years ago and even 50,000 years ago. In addition to matching dates, in Siberia and Alaska and the Yukon there are similar cultural traits. Humans on both sides of Beringia were hunting large game, including mammoths. It is also believed that the technology of foreshafts seen at sites like Yana RHS in Siberia were brought over into America. This deep in prehistory, human hunters are using spears for large game. Atlatls and bows are distant technologies that will not exist for tens of thousands of years yet in the future. Foreshafts help to protect the main spear shaft from damage after a strike. The hunter can quickly replace the point on the end of his spear without having to manufacture a new spear each time he throws it. Let's take a wide view of the whole world and turn back the clock to about 40,000 years ago to giant glacial masses and low sea levels. We have seen sites near Dawson Yukon that have pushed back human occupation in the far northwest, modern Alaska and Yukon, to an older Pleistocene environment, possibly 40,000 years or more. This era is what we used to call the Ice Age, when anatomically modern humans and atlatls are in Europe and western Asia. By 40,000 years ago, humans are also in Australia, as discovered in numerous sites there like Willandra Lakes, a site that dates to 40,000 years ago. The Australian expansion required boats, which is relevant to the discussion on North America. We will zoom back into Beringia and North America. It's easy to see how Siberian cultures could move over Beringia during the last glacial maximum period. We have sites in Siberia and contemporaneous sites in Yukon. However, the next two sites are much more controversial and require more explanation. La Sena in south-central Nebraska and Lovewell in north-central Kansas are mammoth sites from middle America. The mammoth bones at these sites exhibit fractures that appear to be caused by humans. These sites date back to 19,000 years ago. These two middle American sites present a great logistical question. While the Yukon sites at Bluefish Cave and Old Crow are easy to explain by land bridge crossings, the discovery of cut mammoth bones in Nebraska at La Sena and in Kansas at Lovewell require further explanation. The Kansas and Nebraska sites date from the last glacial maximum nearly 20,000 years ago. Between Beringia and the Great Plains is a glacial mass at least one or two miles high that covers essentially all of modern Canada. Thus, a land route and even a water route from Alaska to the lower plains would have been blocked by glaciers. The glaciers will melt back after 20,000 years ago, but it is a long process requiring thousands of years before the corridor opens through Canada, allowing for human migration from Beringia to the Great Plains. But the corridor will not be open until about 12,000 years ago. So how are mammoth bones being fractured by humans in Kansas and Nebraska thousands of years before the corridor opens? We will zoom into the northwestern North America and tilt the viewpoint northward to fit the landscape. Dawson, Yukon is here. La Sena, Nebraska is here. Lovewell, Kansas is here. Let's turn the clock back to the last glacial maximum 20,000 years ago. The answer to our problem requires a major rethinking of the time scale of human occupation in America. At 20,000 years, the path from Yukon to Nebraska is closed by both land and by sea, and it will be closed for thousands of years. If we follow the traditional time scale and wait for the land and sea routes to open about 12,000 years ago, we do not explain how people are hunting mammoths in the Great Plains 19,000 years ago. The problem with this model is we already have people living in America thousands of years before the Clovis culture. However, if we go backward instead of forward in time, if we go before the last glacial maximum to say 26,000 years ago, we can see avenues opening up between Beringia and North America for land and sea travel. By going backward in time, we find a solution to early sites in lower North America. Now we are at 26,000 years ago, a time before the glacial maximum. We now have two possible routes available from Beringia to the Great Plains. One is by land through Canada, and the other is by boat along the Pacific coast, similar to the boat culture expansion seen in Australia. Whether the first Americans used the land or water route or both is paradigm shifting, because in both cases we have to turn the settlement clock back before the glacial maximum to have sites in middle America this old. A pre-glacial maximum migration is sharply contrasted with the earlier model of American settlement that dominated for decades. In the traditional model, humans could only populate middle America after the ice retreated about 12,000 years ago. In this older model, often called Clovis I, human occupation of North America begins about 12,000 years ago. There is significant evidence that original occupation of middle America occurred before, not after, the glacial maximum period. This effectively doubles the time of human occupation in middle North America, explaining sites like Lovewell and La Sena in the Great Plains. In this context, the Clovis culture of 12,000 years ago is actually a much later fluorescence of human culture in America, not the beginning. With the clock turned back to 26,000 years ago, the Canadian land corridor and the Pacific coast corridor have opened. It's now possible to imagine small groups of hunters and gatherers migrating from Beringia into North America through an open corridor on land before the closing of the corridor during the last glacial maximum 20,000 years ago. So at the time of the glacial maximum, there are American populations on both sides of the glacial mass, as seen at Dawson Yukon and at La Sena, Nebraska and Lovewell, Kansas. The Pacific water route is of special significance. Let's zoom back out to the world view. The use of boats in deep prehistory in Australia has pushed boat technology like rafts back tens of thousands of years. Small boats, like rafts or canoes, could have followed the now submerged ancient coastline along western North America. As with the overland route through Canada, if we turn the clock back before the last glacial maximum, the Canadian coastline is no longer covered by ice, allowing for boat people to utilize an ice-free coastline. This Pacific route explains how people quickly got to Central and South America. It's possible that both routes were utilized before the last glacial maximum, and if both routes were utilized, we would essentially have, at the very least, two very different cultures in deep prehistoric North America. An overland culture would consist of hunters and gatherers who likely hunted big game, as shown by fractured mammoth bones almost 20,000 years ago in the American Midwest. On the other hand, the Pacific boat people would be a very different culture. Instead of big game hunters, this kind of culture would focus on fish, shellfish, and other water resources, as well as berries, nuts, and small game from the land. In sum, there's evidence that people migrated from Siberia into modern Alaska and Yukon in deep prehistory as early as 40,000 or more years ago. About 20,000 years ago, the pathway through Canada was blocked by ice during the glacial maximum. However, early dates in America are possible if we imagine migrations before the glacial maximum period when these land and water corridors would have been open, possibly as early as 25,000 years ago or earlier. Thus, mammoth hunters are present at least 19,000 years ago in the Great Plains.