March 04, 2008

Single origin of Native Americans based on full mtDNA sequencing

You might also want to read East-West cranial differentiation in Central and Northern America and New synthesis on the first arrivals into the New World. The latter study gives a 15kya age for the expansion into the Americas which is comparable to the 18-15kya figure given by the current mtDNA-based study.

Am J Hum Genet. 2008 Feb 27 [Epub ahead of print]

Mitochondrial Population Genomics Supports a Single Pre-Clovis Origin with a Coastal Route for the Peopling of the Americas.

Fagundes NJ, Kanitz R, Eckert R, Valls AC, Bogo MR, Salzano FM, Smith DG, Silva WA Jr, Zago MA, Ribeiro-Dos-Santos AK, Santos SE, Petzl-Erler ML, Bonatto SL.

It is well accepted that the Americas were the last continents reached by modern humans, most likely through Beringia. However, the precise time and mode of the colonization of the New World remain hotly disputed issues. Native American populations exhibit almost exclusively five mitochondrial DNA (mtDNA) haplogroups (A-D and X). Haplogroups A-D are also frequent in Asia, suggesting a northeastern Asian origin of these lineages. However, the differential pattern of distribution and frequency of haplogroup X led some to suggest that it may represent an independent migration to the Americas. Here we show, by using 86 complete mitochondrial genomes, that all Native American haplogroups, including haplogroup X, were part of a single founding population, thereby refuting multiple-migration models. A detailed demographic history of the mtDNA sequences estimated with a Bayesian coalescent method indicates a complex model for the peopling of the Americas, in which the initial differentiation from Asian populations ended with a moderate bottleneck in Beringia during the last glacial maximum (LGM), around approximately 23,000 to approximately 19,000 years ago. Toward the end of the LGM, a strong population expansion started approximately 18,000 and finished approximately 15,000 years ago. These results support a pre-Clovis occupation of the New World, suggesting a rapid settlement of the continent along a Pacific coastal route.



Unknown said...

My belief is that Australoids entered Americas first. A small Caucasoid group might have entered with them! If not then it must have entered with the Amerindians.It is not only the Kennewick Man fossil that indicates that but the Solutrean Hypothesis as well!
The Clovis industry has many resemblances with Solutrean and Magdalenian tools. Now if we consider that Amerindians have Y-DNA Q haplogroups, and that Q emerged from P along with R then we might explain the Chancelade fossil of France as well!
If we suppose that some R haplogroups entered Europe just before the last Ice Age then it is not strange that some "Eskimoid" or "Indianoid" humans have been found during the Magdalenian Epoch as well. Perhaps Chancelade specimens are the ancestors of Amerindians and entered Europe along with their cousins, the carriers of some R Hgs!
When the Ice Age withdrew then these Chancelade people withdrew north with it! The Y-DNA Hg R carriers stayed. That can explain the sudden appearance in the paleoanthropological horizon of Europe of this race but also it can explain its sudden disappearance!
We know that Chancelades appeared in the Magdalenian Epoch and disappeared after that! Thus the correlation of the Clovis industry with some "French" cultures might be explained by this race and its movement. Also that will explain the correlation of R and Q Hgs and the appearance of the latter in the Americas!!!
Finally it will also explain the appearance of mtDNA X haplogroup in Amerindians, a Hg which is considered "Europoid".
I do n't propose this theory as a "magic solution" to the subject but rather as a product of intuition!

Crimson Guard said...

Not exactly sure why there is a near complete absences of Europoid Y chromosomes in the Americas.