On August 12th, a story entitled “The Death of the Bering Strait Theory” opened thus: “Two new studies have now, finally, put an end to the long-held theory that the Americas were populated by ancient peoples who walked across the Bering Strait land-bridge from Asia approximately 15,000 years ago.”
The History Channel posted along the same lines: “A new study challenges the popular theory that the first Ice Age humans who migrated to North America arrived by a land bridge that once linked Siberia and Alaska over the Bering Strait.”
As more and more similar stories popped up, I felt a mounting sense of exasperation. I had to remind myself that it’s not my job to correct everyone who’s wrong on the Internet, especially when all the comments rolled in: “I’ve known this all along — it was such a ridiculous theory”, and so on. When I had seen the embargoed press release that generated these stories, I’d been mistaken, too. I read on because I was having trouble picturing a workable alternative to the Bering Strait route. But a thorough reading of the study left the “Bering Strait Theory” firmly intact. The new evidence in no way challenges it.
What actually happened was this: A team based at the University of Copenhagen looked at DNA from sediment cores in a frozen lake in British Columbia. As the two giant ice sheets that covered most of North America — the Cordilleran and Laurentide — began to retreat about 13,000 years ago, a 1,500km ice-free corridor opened up, running all the way from Alaska to Northern Montana. This ice-free corridor was the stage of the journey being thrown into question, and the lake was one of the last points to thaw along that path.
What the DNA showed was that the people who had already crossed the Bering Strait could only have started migrating south along the ice-free corridor something like 12,600 years ago, because there were no plants and animals sufficient to sustain human life until then. Mammoths, bison and rabbits came soon, but not soon enough for the prevailing theory that the first wave of North American habitation from Asia moved south via this route 13,000 years ago. We know that there were people south of Alaska before 12,600 years ago, so the earlier travellers from Beringia likely took a route along the Pacific Coast, concluded the paper.
All this became clear to me after reading the paper, but I can see why the wrong story got out. Though the paper is clearly titled — “Postglacial viability and colonization in North America’s ice-free corridor” — the press release is vaguer: “Textbook story of how humans populated America is ‘biologically unviable,’ study finds”. It opens: “The established theory about the route by which Ice Age peoples first reached the present-day United States has been challenged by an unprecedented study which concludes that their supposed entry route was ‘biologically unviable’”.
If the average person knows anything about how America was first populated, they know that people are supposed to have crossed from Asia over a land bridge during the Ice Age. That’s probably about it. So when you tell them the “established theory” is wrong, this is what they think about. Confusing the Bering Land Bridge with the “ice-free corridor” is even easier given that the latter doesn’t really have a name and the former is kind of corridor-like.
In general, non-specialists are usually satisfied with one point about any given topic about which they have no particular interest. If it makes sense in their narrative of the world, it lodges into their general knowledge in the place where curiosity might have been. Camel humps? Something about storing water in the desert. Never mind that they evolved to store fat for warmth in the Arctic. Michael J. Fox’s middle name? Starts with J. (It’s Andrew).
So when reporting on science, we should keep in mind the party line about our topic and acknowledge it, whether it’s correct or not, and even if it’s irrelevant. Meeting the audience where they stand is the only way to prevent them from automatically applying whatever you tell them to the one fact that springs out at the mention of your topic. It’s all the more important on the Internet, where you lose almost everyone after the third line. Last week’s research announcement was an opportunity for education, but instead many people were led down a blind alley, where they remain.
Image: The Bering Strait/NASA
It gets worse. The ice-free corridor idea had already been reasonably rejected. The News and Views commentary on the paper discusses did, as did the outside source I talked to. So the press release, in opening with “The established theory…” isn’t just badly worded; it’s just plain wrong.
I was wondering about that part. Almost as an aside, it tells us people have been in North America way earlier than any of this, anyway.
What is quite amusing to me is that the idea of coastal migration has always been slow to be considered. Humans naturally follow along the coast, there is tons of food there and usually (but not always) easy going. The fact that all that land is under 300 ft of water, thus making it hard to do archeology, shouldn’t make it a hard theory, but that seems to be what happens. As I recall from the literature, every single attempt that’s been made to explore that area under the sea has turned up artifacts of human nature.
Sorry…noob here trying to get some clarity.
Are you saying the media mistakenly jumped to the conclusion that since there were already people here before ice-free corridor opened up, the Bering Strait land bridge did not exist, instead of reporting that people who crossed the land bridge must have taken an alternate route because of the change in the timing of the corridor?
What the study actually challenged was their route…not their point of entry.
Well said, Jessa. Though, I’ll admit that I didn’t actually register any of it except that one part about which I have no particular interest. Michael J Fox’s middle name is ANDREW??? How was that not your headline?
That needed a bit of work figuring out what was meant. What is worse in my opinion is astronomers discovering an earth-like habitable planet every other week when they have not even seen anything but a wobble in the star or a dimming of its light. This is irresponsible sensationalism.
Alain, as a card-carrying astronomy writer, I can tell you it might have been sensationalism but this time (this time) it wasn’t irresponsible. Unless you’re not talking about extrapolating a planet from the wobble or the dimming, but extrappolating an earth-like habitable planet from the possibility of liquid water — in that case, I’ll back you up on “irresponsible.” At the very least, “over-enthusiastic.”
That the land was completely naked and barren “along the ice-free corridor” is not surprising – because there was not enough carbon dioxide in the atmosphere to support the plant life that is the base for human and animal nutrition.
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The advancing ice sheets increase the Earth’s albedo, reflecting sunlight and resisting natural cyclic warming. As the ice sheets grow and the seas cool, CO2 in the atmosphere reduces as it is absorbed by the oceans. Most plants suffer severe stress at 190 ppm CO2 and die at 150 ppm, because CO2 is a primary plant-food. The concentration finally reaches the critical 190 ppm level where world flora begins to die and the Gobi steppe-lands turn into a true sand desert. The ensuing dust storms dump thousands of tonnes of dust onto the northern ice sheets each year. Ice core data shows that every interglacial warming period is preceded by about 10,000 years of intense dust storms. The dust on the ice absorbs solar radiation. When the next natural warming (or Great Summer) comes along, the dusty polar ice sheets can warm and melt and the next interglacial is born. Low concentrations of CO2 near the end of an ice age causes a die-off of plants leading to dust storms, reducing the ice sheet albedo, resulting in warming and the initiation of the next interglacial period……. see:
http://www.sciencedirect.com/science/article/pii/S1674987116300305
Meanwhile the high amount of carbon dioxide dissolved in sea water was able to sustain the entire aquatic food chain based on photosynthetic phytoplankton so that fish and other sea creatures were available to sustain migrating peoples as they made their way south along the coast of North America.
Peter Salonius