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The History of the North African Mitochondrial DNA Haplogroup U6 Gene Flow Into the African, Eurasian and American Continents


The History of the North African Mitochondrial DNA Haplogroup U6 Gene Flow Into the African, Eurasian and American Continents

Bernard Secher et al. BMC Evol Biol.


Background: Complete mitochondrial DNA (mtDNA) genome analyses have greatly improved the phylogeny and phylogeography of human mtDNA. Human mitochondrial DNA haplogroup U6 has been considered as a molecular signal of a Paleolithic return to North Africa of modern humans from southwestern Asia.

Results: Using 230 complete sequences we have refined the U6 phylogeny, and improved the phylogeographic information by the analysis of 761 partial sequences. This approach provides chronological limits for its arrival to Africa, followed by its spreads there according to climatic fluctuations, and its secondary prehistoric and historic migrations out of Africa colonizing Europe, the Canary Islands and the American Continent.

Conclusions: The U6 expansions and contractions inside Africa faithfully reflect the climatic fluctuations that occurred in this Continent affecting also the Canary Islands. Mediterranean contacts drove these lineages to Europe, at least since the Neolithic. In turn, the European colonization brought different U6 lineages throughout the American Continent leaving the specific sign of the colonizers origin.


Figure 1
Figure 1
Surface maps, based on HVI frequencies (in o/oo), for total U6 (U6), total U6a (Tot U6a), U6a without 16189 (U6a), U6a with 16189 (U6a-189), U6b'd, U6c, U6b and U6d.
Figure 2
Figure 2
Acadian pedigree.
Figure 3
Figure 3
Bayesian Skyline Plots (BSPs) of effective population size (thousands) through time (ky BP) inferred from U6 total (a) and African (b) complete sequences.
Figure 4
Figure 4
Principal Component Analysis (PC) based on U6 subhaplogroup frequencies in the different populations studied. The position occupied by each sub-haplogroup is indicated in gray.

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