[BMorearty]

I'm confused by this article. It says "New evidence adds to work showing people made these prints [in New Mexico] sometime between 21,000 and 23,000 years ago." It supposedly contradicts experts' belief for decades that "the first people in the Americas migrated from Siberia across the Bering Strait on a land bridge exposed during the last glacial maximum, sometime between 26,500 and 19,000 years ago.

How is that contradictory?

[jcranmer]

The traditional thesis of the peopling of the Americas is that people arrive in Beringia (not entirely accurate to say they crossed the Bering Strait--there was no Bering Strait, and Beringia was where the Bering Strait is now!), c. 20-odd thousand years ago. About 13,000 years ago, a gap opens between the Rocky Mountains and the Laurentide Ice Sheet, and settlers traveled through this "ice-free corridor" to reach what is now the US, where they flourish as the Clovis culture. This is known as the Clovis-First hypothesis--that Clovis was the first material culture to leave Beringia and people the rest of the Americas.

However, there's a lot of evidence that people had spread out to the rest of the Americas well before Clovis, and it's now known that the "ice-free corridor" opens up too late--it opens up even after we see traces of Clovis-First. By around the 1990s, the anthropological community has accepted that Clovis-First is complete and utter rubbish, although there is still disagreement about the timetable. I'd wager seriously arguing Clovis-First among scientists would get you as much derision as seriously arguing geocentrism among astronomers.

Annoyingly, popular anthropology lags science tremendously. It probably took a decade or two for textbook writers to bother to update their textbooks to consider the rejection of Clovis-First (hell, when I was in school, the textbook didn't even bother to present alternative hypotheses than Clovis-First, although our teachers were knowledgeable enough to tell us in class that, well, textbook's got it wrong there), and then perhaps another decade for schools to get around to new textbooks. It's still the case that virtually every popular treatment of some new press release about dating controversy in some ancient human habitation site (there's one every year or so) starts, as this article does, by talking about how it potentially nails the coffin for Clovis-First. (Wake up science writers! That coffin's been nailed shut for longer than most of your readers have been alive!)

[civilitty]

To add to that great explanation: those ice free corridors were important because during the glaciation there were vast expanses of ice with zero vegetation or animal life, making it impossible for humans to cross without starving to death. Those glaciers essentially looked like the South Pole - nothing but ice for hundreds of miles. How humans managed to get so far and colonize so much of the continent while it was still iced over is one of the great "mysteries" of the new world.

It took plants and animals thousands of years to colonize Berengia before it was possible for humans to cross the expanse on land so the main competing hypothesis states that the people of Oceania - at this point very capable of navigating at sea and exploiting marine resources - were the first ones to make the trip, hugging the coast of Beringia to navigate and wait out storms but eating seafood caught at sea to stay alive.

Unfortunately the sea level at this point in time was at least 150 ft below and while underwater archaeology has had somewhat of a renaissance, there's still very little evidence to support what many (most?) archaeologists expect is true: human arrival in the Americas predates any evidence we've recovered by many thousands of years.

[BMorearty]

Thank you. That is a much more lucid and complete explanation than was given in the article.

[AlotOfReading]

You couldn't get from beringia to New Mexico during the last glacial maximum because of all glaciers in the way.

The dates given for the LGM are (very roughly) when Beringia was accessible from Siberia. Pinning down when humans were able to access the rest of the continent is tricky, but current estimates for that are sometime between 20-18kya at the earliest based on genetics. Dates based on material culture evidence are even later than that, which presents done obvious problems with the dating on these footprints.

There are also pretty hard constraints on the other side for humans even arriving in that part of Siberia, since the immediate ancestor sites with sequencing at Yana and Mal'ta are from 32kya and 25kya respectively.

[doodlebugging]

If those early people had boats or other means of floating along the coasts they easily could've found their way to present-day New Mexico during the time period in question with or without glaciers in North America. A single family or individual who managed to hug the coast to a point south of the glaciers could easily walk the width of the United States in under a year averaging only 10 miles per day. There is plenty of time for a nomadic person or group following game animals or just walking over the hill to see what they can see to cover the entire United States on foot in a short lifetime. If they have rafts, boats, or any other way of navigating waterways without drowning it is even easier. These people were not stupid and they likely were as curious as we are today. They didn't have the cool technologies that we have today or in the last 200 years but they had a deep knowledge of their environments and could read the landscapes, the skies, the animals, and the plants and understand a lot more than most of today could.

The real question needs to be about how far back we can go and say conclusively that humans built boats, hollowed logs, etc. and used those constructed contraptions to travel over water.

[lumost]

Something that has never sit right with me. Why do we not have clear evidence of past major civilizations in the main habitation zones of modern North America?

Shouldn’t we see ancient cities in New England, the PNW, Bay Area, and southeastern US? What made South America, and the southwestern zone of North America special in this regard?

[diogenes4]

I believe that "sometime between 26,500 and 19,000 years ago" is an appositive marking the beginning of the land bridge's accessibility, not the time of migration. What they should have said is that the broadly accepted conservative time frame for migration is somewhere between 14kya and 19kya, as the white sands footprints have dating issues that complicate accepting them at face value. The liberal interpretations of the evidence—especially in northern Canada and Alaska—can push evidence back to more than 33kya—I've seen dating for 44kya, iirc, which is very contentious and not broadly accepted.

That said I don't have a wapo subscription, so that's my best guess.

[hn_throwaway_99]

You can read WaPo articles if you turn off Javascript.

[hinkley]

It wasn’t so long ago we thought 12500 years was about the right time.

[JKCalhoun]

FWIW, WaPo loads fine for me with Reader turned on (Safari).