Thursday, November 8, 2018

Regarding Ed Yong's Article in the Atlantic "The Extremely Fast Peopling of the Americas"

Today, two papers were published on the genetic history of Native Americans, one by J. Víctor Moreno-Mayar et al., from the University of Copenhagen, and another by Cosimo Posth et al. at the Max Planck Institute in Germany.  The samples are based on genetic data in North and South America from about 14,000 years ago onward.

While it is certainly interesting to know more about the population dynamics in the Americas after the Ice Age, these papers tell us little about population dynamics between Eurasia and the Americas in the time period of interest before 14,000 years ago.

Ed Yong's article in the Atlantic discusses both papers.  It starts with a discussion about the Ice Age in North America:

"Tens of thousands of years ago, two gigantic ice sheets smothered the northernmost parts of what has since been named North America. They towered more than two kilometers high and contained 1.5 times as much water as Antarctica does today. They were daunting, impassable barriers to the early humans who had started moving east from Asia, walking across a land bridge that once connected the regions now known as Russia and Alaska."

I don't know where Ed Yong got his information from, but before 22,000 years ago, there was no "daunting, impassible barrier" at all between North America and Beringia.  That's according to expert Canadian geologist Lionel Jackson:

Progressive Westward Expansion of North American Continental Ice Sheets During The Quaternery and Implications for the Timing of Initial Human Overland Migration Into the Americas
Jackson Jr, Lionel E.,
2014 Annual Meeting,
The Geological Society of America
19-22 October, 2014
Paper No. 137-3

We know that humans were living in North America at the Bluefish Caves site (24,000 years ago in the Yukon):

Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada
Lauriane Bourgeon, Ariane Burke, Thomas Higham
January 6th, 2017

If there were humans in the Yukon 24,000 years ago, then there very likely were humans living a thousand miles south (at least) as well.  The reason that you never hear about this is that North American archaeologists have asserted human presence in the Americas primarily from refined points such as Western Stemmed points, and Clovis Points.  Recently, there have been a few sites in North America with refined points dated to about 18,000 years ago, which shows that humans were present south of the Ice before the opening of the Ice Free corridor about 15,000 years ago.  Many archeologists have questioned the use of only refined points to assert when humans entered North America. A good alternative view on Paleolithic archaeology in North America is discussed by Jiří Chlachula in this paper:

Geoarchaeology of Palaeo-American Sites in Pleistocene Glacigenic Deposits

So the discussion of the Beringia land bridge and the Ice Free corridor in Ed's article is likely somewhat peripheral to the population expansion discussed in these papers.  The first entry of humans into the Americas south of the Cordilleran/Laurentide Ice Sheet cannot be assumed to be after 18,000 years ago.  There is no doubt that something was going on in North America between 14,000 and 10,000 years ago:  The Clovis Culture emerged, many large mammals went extinct, and the Younger Dryas led to extreme climate variability.  Any of these events could have been cause for an expansion of the North American population southward.  But to say that these papers indicate an "Extremely Fast Peopling of the Americans" is dubious at best, and taking a less generous view, intentionally misleading.


DDeden said...

"Since there appears to be a renewed interest in the genomes of Native Americans who had mtDNA D4h3a haplotypes, I would like to reiterate that no D4h3 sequences have ever been reported in Siberia. The two complete Asian D4h3 sequences in the database are from the Shandong peninsula and northern Thailand."

Marnie said...

"no D4h3 sequences have ever been reported in Siberia"

The Japan/Hokkaido/Kuril/Aleutian Island route is an alternative Trans Pacific route, that could have been used (in addition to Beringia).


"Maritime Transport of Obsidian in Japan during the Upper Paleolithic"

Two Islands in the Ocean: Prehistoric Obsidian Exchange between Sakhalin and Hokkaido, Northeast Asia


I don't think that adequate consideration has been given to the idea that if people were pushing up into Sakhalin 20,000 years ago (when the sea level was 200 meters lower), it probably wouldn't have been that difficult to get onto the Aleutian Islands chain, and get access to the obsidian sources in Alaska, the Yukon, etc.

The remains of the On Your Knees Cave person (Prince of Wales Island on the Alaska panhandle) is dated to 10.3 kya. His mtDNA sequence was D4h3a.

And, what do you know, there is an obsidian source near Prince of Wales Island on Suemez Island:

D4h3a also appears among Patagonians, and what do you know, there are a number of obsidian sources in Patagonia.

So, I think that so long as the sea level was lower, allowing easier sea crossings between Sakhalin and the Alaska (through the Aleutian Islands), it was probably quite a regular thing for people to be crossing back and fourth across the Pacific.

I think that is one reason why we see these trans Pacific DNA distributions, D4h3a being one of them.