American Settlement Now Pushed Back to 23,000 BC

[Desiree]

Public Release: 21-Jul-2015
Genome analysis pins down arrival and spread of first Americans

Comparing current and ancient genomes shows Siberian migration no earlier than 23,000 years ago

University of California - Berkeley


IMAGE: This is an artist's representation of the ice age landscape that early Native Americans would have encountered. view more

Credit: Artwork by Sussi Bech

The original Americans came from Siberia in a single wave no more than 23,000 years ago, at the height of the last Ice Age, and apparently hung out in the north - perhaps for thousands of years - before spreading in two distinct populations throughout North and South America, according to a new genomic analysis.

The findings, which will be reported in the July 24 issue of Science, confirm the most popular theory of the peopling of the Americas, but throws cold water on others, including the notion of an earlier wave of people from East Asia prior to the last glacial maximum, and the idea that multiple independent waves produced the major subgroups of Native Americans we see today, as opposed to diversification in the Americas.

This Ice Age migration over a land bridge between Siberia and Alaska is distinct from the arrival of the Inuit and Eskimo, who were latecomers, spreading throughout the Artic beginning about 5,500 years ago.

The findings also dispel the idea that Polynesians or Europeans contributed to the genetic heritage of Native Americans.

The analysis, using the most comprehensive genetic data set from Native Americans to date, was conducted using three different statistical models, two of them created by UC Berkeley researchers. The first, developed by the lab of Yun Song, a UC Berkeley associate professor of statistics and of electrical engineering and computer sciences, takes into account the full DNA information available from the genomes in the study. A second method, developed by Rasmus Nielsen, a UC Berkeley professor of integrative biology, and graduate student Kelley Harris, requires much less computation, but relies on a summary of the genome data. These and a third method developed by researchers at the Wellcome Trust Sanger Institute, England, all yielded consistent results. Song and Nielsen are two of three corresponding authors of the paper.

Modern and ancient genomes

The data consisted of the sequenced genomes of 31 living Native Americans, Siberians and people from around the Pacific Ocean, and the genomes of 23 ancient individuals from North and South America, spanning a time between 200 and 6,000 years ago.

"There is some uncertainty in the dates of the migration and the divergence between the norther and southern Amerindian populations," Song noted, "but as we get more ancient genomes sequenced, we will be able to put more precise dates on the times of migration."

The international team concluded that the northern and southern Native American populations diverged between 11,500 and 14,500 years ago, with the northern branch leading to the present day Athabascans and Amerindians broadly distributed throughout North America. The southern branch peopled Central and South America, as well as part of northern North America.

"The diversification of modern Native Americans appears to have started around 13,000 years ago when the first unique Native American culture appears in the archeological record: the Clovis culture," said Nielsen. "We can date this split so precisely in part because we previously have analyzed the 12,600-year-old remains of a boy associated with the Clovis culture."

One surprise in the genetic data is that both populations of Native Americans have a small admixture of genes from East Asians and Australo-Melanesians, including Papuans, Solomon Islanders and Southeast Asian hunter gatherers.

"It's a surprising finding and it implies that New World populations were not completely isolated from the Old World after their initial migration," said Eske Willerslev from the Centre for GeoGenetics at the Natural History Museum, University of Copenhagen, who headed the study. "We cannot say exactly how and when this gene flow happened, but one possibility is that it came through the Aleutian Islanders living off the coast of Alaska."

Song added that the state-of-the-art statistical methods that his and Nielsen's labs developed "are being made publicly available so that they can be used by others to study complex demographic histories of other populations."

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Media Contact

Robert Sanders
rlsanders@berkeley.edu
510-643-6998

 @UCBerkeleyNews

http://www.berkeley.edu


http://www.eurekalert.org/pub_releases/2015-07/uoc--gap072115.php

[Desiree]

New light on first peopling of the Americas

Tue, Jul 21, 2015

Genetic research shows a single, not multiple, wave migration of ancestors no more than 23,000 years ago.
New light on first peopling of the Americas

In what could turn out to be a landmark study, researchers have pieced together a new picture of how and when the ancestors of present-day Native Americans entered the Americas.

Using genetic data from the remains of ancient individuals as well as that of modern individuals, Maanasa Raghaven of the University of Copenhagen and colleagues from an international array of multiple institutions sequenced and compared the genomes of ancient and modern individuals from the Americas, Siberia, and Oceania, including the application of a range of analyses that also leveraged previously published genomic datasets from Europe and Africa.

The results of their analysis suggested that the earliest, Late Pleistocene ancestors of Native Americans entered the Americas in a single wave from a single source population—not in multiple waves from different, geographically disparate population sources, as some scholars have suggested. Moreover, they estimate that this group migrated from Siberia to the Americas no earlier than 23,000 years ago, during the harsh and frigid Last Glacial Maximum – and after no more than 8,000 years of isolation from the ancestral Siberian population. The study results also suggest that present-day genetic differences were due to genetic changes or events occuring after the initial migration.

"Our results show the Siberian Yupik and Koryak are the closest Eurasian populations to the Americas, with the Yupik likely representing back-migration of the Inuit into Siberia," stated the authors in the study report. Using demographic models, they also suggested that "the split of Native Americans (including Amerindians and Athabascans) from the Koryak dates to ca. 20 kya."*   

Though it is generally accepted that ancestors of modern-day Native Americans descended from Siberians who crossed the Bering Land Bridge, the exact timing and pattern of entry has been hotly debated, revolving around the issues of when ancestral Native Americans left Siberia, whether they came to the Americas in one wave or multiple (with multiple times explaining the current genetic diversity), and how long they spent isolated in the Bering Strait region before arriving, with one model (the Beringian Incubation Model) suggesting as much as 15,000 years.

Perhaps most significantly, their findings lend further support to a pre-Clovis presence of humans in the Americas, a subject of great debate over the years among scholars. Mounting archaeological evidence over the past few decades, however, have provided increasing support to those challenging the Clovis First theory, which advances the notion that the earliest peoples who entered the Americas were associated with a distinct stone tool industry or culture with an earliest date of approximately 12.6 kya.

But the research also shows a major twist in the genetic journey of the earliest Americans—specifically, that the group split off into two branches around 13,000 years ago, coinciding with glacier melt and the opening of routes into North America's interior, combined with additional admixture leading to the diversity of Native American populations we see today:

"The data presented here are consistent with a single initial migration of all Native Americans and with later gene flow from sources related to East Asians and, more distantly, Australo-Melanesians. From that single migration, there was a diversification of ancestral Native Americans leading to the formation of ‘northern’[ancestors of the Athabascans and northern Amerindian groups] and ‘southern’[Amerindians from southern North America and Central and South America] branches, which appears to have taken place ca. 13 KYA within the Americas."*

________________________________________

nativeamaricanspic1Origins and population history of Native Americans, based on the research by Raghavan et al. [Credit: Raghavan et al., Science (2015)]

________________________________________

The research paper is published with free access in the 23 July issue of Science Express, a publication of the American Association for the Advancement of Science (AAAS).

________________________________________

* Maanasa Raghaven, et al., Genomic evidence for the Pleistocene and recent population history of Native Americans, Science Express, 23 July 2015

Some content for this article was adapted and edited from the related AAAS press release.

[Desiree]

[Desiree]

[Desiree]

Well within the time frame of Atlantis!

Take that, supporters of the Clovis first theory (if there any out there apart from the approaching senior citizen academics).

[freetoroam]

The study authors wrote: "The diversification of modern Native Americans appears to have started around 13,000 years ago when the first unique Native American culture appears in the archeological record: the Clovis culture," said Nielsen. "We can date this split so precisely in part because we previously have analyzed the 12,600-year-old remains of a boy associated with the Clovis culture." That seems to support Clovis First.

[Kaleidoscope]

Yes, when taken out of context, you observation appears to be correct. However, not when one reads the entire article. The operative word in the quoted statement is 'diversification". That does not preclude a pre-Clovis culture before the diversification. There is already much archaeological evidence supporting a pre-Clovis culture in the Americas, though it is not as well defined as the Clovis.

[Caitlin Cone-Hoskins]

I did read the article Popular Archaeology (PA)wrote and the better written article in AAAS]EurekAlert! PA of course said that the study lends support against Clovis First but that is NOT what the study said. The study "...... when the first unique Native American culture appears in the archeological record...". There is some disputed evidence of pre-Clovis. Problem with the evidence is not one site supports any other pre-Clovis site. Even the dates range from 33,000 to 14000. That seems to contradict human nature. Hunters finding themselves in a paradise of large animals unafraid of humans would have spread like wild fire. The only disease would have been what they brought with them. One guy calculated that a small band would have grown to populate both continents in 350 years.

[Out of Sight, Out of Mind]

I suppose "better written article"is a highly debatable topic, but that is beside the point of this discussion: I quote from the research paper itself: "This result is consistent with the model that people entered the Americas prior to the development of the Clovis complex and had reached as far as southern South America by 14.6 KYA" But I suppose it also depends on how one defines what is meant by "Clovis First".

[A Flock of Seagulls]

In regards to your quote from the "research paper itself", you left out the first part, "though consensus has yet to be reached,..." Consensus is defined as agreement. There is no agreement that Clovis First is wrong. There are a bunch of people who who would like it dead... Mormons who think native Americans are the lost tribes of Israel, to native Americans who think they were created here, to feminist who think a male dominated "blitzkrieg" of America is offensive and a whole bunch of archeologist who can pull funding from those groups.

[Back to Earth]

Now you're grasping at straws. Whether or not there is "consensus" among the scientific establishment regarding the arguments for and against Clovis First was never the issue here. The fact remains, regardless of whether or not there is "consensus" among the scholars, the authors of the report still make the point that their results are consistent with the model that people entered the Americas prior to the development of the Clovis complex. (And if you knew anything about the Mormons, you would know that they do not claim that the Native Americans are the lost tribes of Israel-- a total misrepresentation of what they believe.) We've belabored this long enough.....let's move on to more productive pursuits.