Human Migration to the Americas

Podcast Transcript

Perhaps the most important research in anthropology is how modern humans left their birthplace in Africa and migrated to the rest of the world.

One big subset of that story is how humans managed to get to the Americas.

It is a tale that has resulted in theories being updated several times based on new evidence.

Learn more about human migration to the Americans and our current best guess as to how it happened on this episode of Everything Everywhere Daily.

One of the reasons why human migration to the Americas is such a mystery is that for thousands of years, the peoples of the eastern and western hemispheres had pretty much no clue that the others existed.

There was effectively no contact between these two halves of humanity.

Because of the isolation of the Americas, it was natural to wonder how people got there in the first place.

Figuring out this riddle involved almost every area of science. Geology, genetics, archeology, anthropology, and many other disciplines.

The first iteration of the story is probably one you’ve heard before, and it touches on several previous episodes I’ve done before.

Here it is in a nutshell:

About 70,000 years ago or so, one or more migrations out of Africa occurred. These people spread chasing game and also moving when there was no game to hunt. Over the course of tens of thousands of years, this resulted in the settlement of most of the landmasses in the eastern hemisphere. I previously did an episode that went into more depth on this subject.

The second part of the story has to do with the most recent ice age.

An enormous ice sheet, several kilometers thick, amassed in the northern hemisphere. This ice sheet locked up a large part of the Earth’s surface water, which resulted in sea levels dropping.

Sea levels were about 122 meters or 400 feet lower than what they are today. That means there were large parts of what is now the sea floor which was exposed as dry land.

In particular, in the Bering Strait, the newly exposed land connected North America and Asia. This land bridge is known as Beringia.

Then about 13,000 years ago, humans migrated over the land bridge during the ice age into North America.

When the ice age ended about 11,700 years ago, the land bridge disappeared, and the humans that were in North America could not now go back into Asia the way they came.

Over the last several thousand years, humans slowly migrated from Alaska down to Patagonia.

This was the original story that fit the facts as they were known and perhaps the one which you’ve heard of.

Much of this theory came from the discovery of paleolithic human fossils, which were discovered in the 1930s near the town of Clovis, New Mexico. These remains and the associated spear points became known as the Clovis Culture.

These remains were dated to be around 12,700 to 13,400 years old.

Because nothing was ever found that was older than the Clovis Culture, this developed into the Clovis First hypothesis.

The Clovis First hypothesis held that the Clovis People were the first to migrate to the Americas, which is why the date for the migration was set at approximately 13,000 years ago.

Cracks in the Clovis Hypothesis began to appear when more remains were found which didn’t fit the timeline.

In 2006, a dig site in Buttermilk Creek, Texas, found artifacts below the stratigraphic layer where Clovis artifacts were found. These objects were dated back 15,500 years ago.

This was just the first of several such sites discovered all over North and South America, which were dated to before the Clovis Culture.

There was a great deal of resistance to overturning the Clovis First hypothesis amongst anthropologists. This was the theory that they had been taught at university, and one single dig site wasn’t necessarily enough to overturn a theory that had been dominant for decades.

However, Buttermilk Creek was just of many pre-Clovis sites which was discovered.

Discoveries were made in the Channel Islands in California, which was dated back 12,500 years ago. Far later than expected for a site that far south.

In Monte Verde, southern Chile, a site was found that dated back 14,500 to 18,500 years ago, well out of the bounds for a Clovis Culture site and far further south than would be possible under the Clovis First hypothesis. For humans to make it this far south implies that humans had to have entered the Americas far earlier.

A site in South Carolina was found to date back 22,900 years and possibly as far as 50,000 years, although that date is in doubt.

Paisley Caves in Oregon had remains that were found to be at least 1,000 years older than Clovis.

A site in Brazil, Pedra Furada, had charcoal which was dated back 32,000 to 48,000 years ago.

A site at Tlapacoya, Mexico, was found to date back to 22,000 to 24,000 years.

Ancient fossilized human footprints in White Sands National Park in New Mexico have been dated back 22,000 to 24,000 years as well.

I can’t even go through all the pre-Clovis sites which were found, but suffice it to say that there has been a lot of them found now. Additional sites in Alaska, Yukon, Washington, Virginia, Idaho, Pennsylvania, Colombia, and Peru have all been dated before the 13,000-year Clovis mark, and many are much older than Clovis.

This new evidence has caused a rethinking of just how humans arrived in the Americas.

Here I need to reiterate that a theory is just an explanation to explain the facts. With new facts, there have been new theories proposed to try and fit the new facts.

One theory is known as the Coastal Migration Route.

This idea holds that Humans were able to spread rapidly down the Pacific Coast because they traveled by sea. They used small boats, rafts, or kayaks to work their way down the coast, where they would have got their sustenance from abundant marine life.

This allowed them to spread relatively rapidly down the west coast of the Americas, where they could have reached South America in just a few centuries or maybe even decades.

There is also evidence that the coast of Beringia was ice-free during the last ice age, which would have made this type of transportation possible.

The problem is, while this fits the facts, there is no direct evidence of any sea transportation.

Almost all of the archeological sites which could possibly prove this would have been lost when the sea levels rose. It would explain a lot about why it took so long to find pre-Clovis sites.

Another hypothesis is known as the Solutrean Hypothesis. This says that the first very early migrants to the Americas didn’t come from Asia but came from Europe.

The Solutreans were the people who created cave paintings in southern Europe.

The theory holds that people from Europe traveled through pack ice in the North Atlantic and arrived in the Americas that way.

The evidence for this is pretty slim at well. It mostly comes from the similarities between spearheads found in Clovis and pre-Clovis sites and those found in Europe. Most anthropologists don’t believe in this theory, and it isn’t well supported by genetics.

Genetic testing of Native Americans has found that they all share genes with native people who live in Siberia. However, some distant mitochondrial genes are shared with Europeans, but those just as easily could have come from transmission across Eurasia.

Another theory tries to reconcile the late arrival of humans to the Americas with the much earlier arrival of humans in Siberia. This is called the Beringian Standstill Hypothesis. This basically holds that humans hung out in Beringia for thousands of years before heading into North America.

Beringia would have been grassland and forest at the time and would have been populated with megafauna. It probably would have been a great hunting ground.

So it is possible that they did walk across the land bridge but just did so earlier than assumed.

If all of this seems confusing, there is even more.

It is entirely possible that there wasn’t just a single migration. There could have been multiple migrations over a period of thousands of years. There could have been multiple cultures that migrated, all of which had slightly different spear points, which are represented in the archeological record.

Then, just to really throw a spanner into the works, in 2017, there were mastodon bones found at an archeological dig near San Diego. The bones date back 130,000 years, and some researchers think that there are marks on the bones that show evidence of fracturing, which come from rocks hammering the bones.

I should point out that this evidence is far from universally accepted. This is by no means conclusive proof and may, in fact, not even be proof at all. To establish a human presence in the Americas that far back would require much more than marks on bones, and so far, there is nothing.

I should also address one other route that humans used to reach the Americans, although they aren’t quite as relevant to the story.

The evidence of Polynesians having reached South America is pretty strong. There is some Polynesian DNA that has been found in people in South America, as well as genetic evidence from the remains of chickens.

If you remember back to my episode on Polynesian navigators, they were the best open-water navigators in the world prior to the 15th century. They made it as far as Easter Island, so it isn’t at all a stretch for them to have reached the coast of South America. In fact, given how much they traveled in the Pacific, it would be shocking if they didn’t reach the coast of South America.

However, this would have occurred 600 to 800 years ago, before Columbus, but at a point where humans were in South America for thousands of years.

There is also, of course, the Vikings who managed to make it to Newfoundland about 1,000 years ago. They too, didn’t stay very long and had no long-term impact.

The big-picture story of humans coming from Siberia into North America is largely confirmed. This is overwhelmingly confirmed by the genetic comparison of native Americans and native Siberians.

Furthermore, the evidence is now quite strong that pre-Clovis people in the Americas existed, and quite possibly, well before Clovis. I would expect more evidence for pre-Clovis people to be found over the next several years.

The big question now is when they arrived, how they arrived, and how many times they arrived.

The Coastal Migration Route theory seems to be the most popular theory currently, but it is far from universally accepted, and there is a lot more evidence which would be needed to conclusively prove it.

We seem to be at an odd time right now in terms of understanding human migration to the Americas.

There is enough evidence to prove the Clovis First theory wrong, but there isn’t enough evidence to conclusively prove anything else.

The story of how humans arrived in the Americas is a fascinating story, but it is a story that isn’t yet complete. Whatever twists and turns the story takes over the next several decades, as more evidence is collected, it is sure to be interesting.

The Executive Producer of Everything Everywhere Daily is Charles Daniel.

The associate producers are Thor Thomsen and Peter Bennett.

Today’s review comes from listener Mattsotheraccount over on Apple Podcasts in Australia. They write:

Such a great Pod!

This is such a great podcast. I love every episode and wish there could be more than just one a day.

I was particularly impressed by the Paris episode. Having worked in the city as a guide for years, somehow Gary condensed almost everything I’d share in a four-hour tour in under 15 minutes; it was fantastic. But then they all are!! I can’t wait for the next episode.

Thanks, Matt! I’m glad I’ve met your Paris tour guide’s seal of approval. Episodes like the Paris one are always difficult because I have to cram so much into a single short episode.

Remember, if you leave a review or send me a boostagram, you too can have it read on the show.