Posted on 11/26/2007 4:13:41 PM PST by blam
Contact: Anne Rueter
arueter@umich.edu
734-764-2220
University of Michigan Health System
11-26-2007
Gene study supports single main migration across Bering Strait
Siberians and Native Americans share unique genetic variant
The U-M study, which analyzed genetic data from 29 Native American populations, suggests a Siberian origin is much more likely than a South Asian or Polynesian origin.
Did a relatively small number of people from Siberia who trekked across a Bering Strait land bridge some 12,000 years ago give rise to the native peoples of North and South America?
Or did the ancestors of today’s native peoples come from other parts of Asia or Polynesia, arriving multiple times at several places on the two continents, by sea as well as by land, in successive migrations that began as early as 30,000 years ago?
The questions – featured on magazine covers and TV specials – have agitated anthropologists, archaeologists and others for decades.
University of Michigan scientists, working with an international team of geneticists and anthropologists, have produced new genetic evidence that’s likely to hearten proponents of the land bridge theory. The study, published online in PLoS Genetics, is one of the most comprehensive analyses so far among efforts to use genetic data to shed light on the topic.
The researchers examined genetic variation at 678 key locations or markers in the DNA of present-day members of 29 Native American populations across North, Central and South America. They also analyzed data from two Siberian groups. The analysis shows:
o genetic diversity, as well as genetic similarity to the Siberian groups, decreases the farther a native population is from the Bering Strait – adding to existing archaeological and genetic evidence that the ancestors of native North and South Americans came by the northwest route.
o a unique genetic variant is widespread in Native Americans across both American continents – suggesting that the first humans in the Americas came in a single migration or multiple waves from a single source, not in waves of migrations from different sources. The variant, which is not part of a gene and has no biological function, has not been found in genetic studies of people elsewhere in the world except eastern Siberia.
The researchers say the variant likely occurred shortly prior to migration to the Americas, or immediately afterwards.
“We have reasonably clear genetic evidence that the most likely candidate for the source of Native American populations is somewhere in east Asia,” says Noah A. Rosenberg, Ph.D., assistant professor of human genetics and assistant research professor of bioinformatics at the Center for Computational Medicine and Biology at the U-M Medical School and assistant research professor at the U-M Life Sciences Institute.
“If there were a large number of migrations, and most of the source groups didn’t have the variant, then we would not see the widespread presence of the mutation in the Americas,” he says.
Rosenberg has previously studied the same set of 678 genetic markers used in the new study in 50 populations around the world, to learn which populations are genetically similar and what migration patterns might explain the similarities. For North and South America, the current research breaks new ground by looking at a large number of native populations using a large number of markers.
The pattern the research uncovered – that as the founding populations moved south from the Bering Strait, genetic diversity declined – is what one would expect when migration is relatively recent, says Mattias Jakobsson, Ph.D., co-first author of the paper and a post-doctoral fellow in human genetics at the U-M Medical School and the U-M Center for Computational Medicine and Biology. There has not been time yet for mutations that typically occur over longer periods to diversify the gene pool.
In addition, the study’s findings hint at supporting evidence for scholars who believe early inhabitants followed the coasts to spread south into South America, rather than moving in waves across the interior.
“Assuming a migration route along the coast provides a slightly better fit with the pattern we see in genetic diversity,” Rosenberg says.
The study also found that:
Populations in the Andes and Central America showed genetic similarities.
Populations from western South America showed more genetic variation than populations from eastern South America.
Among closely related populations, the ones more similar linguistically were also more similar genetically.
GGG Ping.
These immigrants had boats. Walking from Alaska to anywhere south would have been near impossible.
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Proving something EVERY Minnesotan knows...they were just trying to get the heck out of Syberia ASAP...they were FREEZING!
Whoops, these guys didn't consider the "reverse migration" thesis. Must mean these fellows don't want it to be thought that early Americans knew how to build boats.
Well, one step forward and two steps back.
Must be some huge investment in the land bridge theory that they just don’t want to let go of. Considering that you’ve got some of the richest waters for sea life off the coast, it’d take a truly dedicated hunter to chase after mammoths or whatever the excuse is this week.
They wouldn’t need to. But the study seems to greatly discount the Polynesian contribution which has a lot of reference to SA language, etc.
I believe they would. A whole lot of European genes would mess up this study.
Mitochondrial DNA is passed unchanged (except for occasional mutations) from mother to children. Mixing with Europeans would either retain the original Native American mtDNA (European male, Native American mother), or retain the European mtDNA (Native American male, European mother). There would be no intermediate mtDNA formed.
And those occasional mutations? That is what this study focused on to track the population movements.
NordP
This complements the Tamm et al. (2007) article that came out a couple of months ago.
I used Europeans as an example but what about Polynesians who may have emigrated to America in the 1700s aboard commercial ships? What if they had children with native Americans or native Mexicans in the colonial period? Testing their descendants for the influence of external DNA would be most problematic.
I believe this is a valid study, but I also believe that some sort of precautions would need to have been taken to obtain genetically pure native DNA.
They wouldn’t need to have a pure sample to find the code. For the same reason, the Welsh are found to have first appeared in what is now Hungary. It would be hard to find “purity” in any stock
Hmmm, how does this fit in with the study of Eskimo dentition? From living Eskimos to fossil evidence, there seems to have been 3 different waves, as to teeth types/patterns, that developed in the arctic populations.
Now that I'm "out" of MN...I won't live ANYwhere that palm trees don't grow. ;-)
Lovely people in cold places...but just can't live there anymore myself.
I believe Kennewick Man has sundadont teeth.
Humans trade the girls. So do our cousins the chimps.
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