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. 2012 Dec 3;12:234.
doi: 10.1186/1471-2148-12-234.

Divorcing the Late Upper Palaeolithic Demographic Histories of mtDNA Haplogroups M1 and U6 in Africa

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Free PMC article

Divorcing the Late Upper Palaeolithic Demographic Histories of mtDNA Haplogroups M1 and U6 in Africa

Erwan Pennarun et al. BMC Evol Biol. .
Free PMC article

Abstract

Background: A Southwest Asian origin and dispersal to North Africa in the Early Upper Palaeolithic era has been inferred in previous studies for mtDNA haplogroups M1 and U6. Both haplogroups have been proposed to show similar geographic patterns and shared demographic histories.

Results: We report here 24 M1 and 33 U6 new complete mtDNA sequences that allow us to refine the existing phylogeny of these haplogroups. The resulting phylogenetic information was used to genotype a further 131 M1 and 91 U6 samples to determine the geographic spread of their sub-clades. No southwest Asian specific clades for M1 or U6 were discovered. U6 and M1 frequencies in North Africa, the Middle East and Europe do not follow similar patterns, and their sub-clade divisions do not appear to be compatible with their shared history reaching back to the Early Upper Palaeolithic. The Bayesian Skyline Plots testify to non-overlapping phases of expansion, and the haplogroups' phylogenies suggest that there are U6 sub-clades that expanded earlier than those in M1. Some M1 and U6 sub-clades could be linked with certain events. For example, U6a1 and M1b, with their coalescent ages of ~20,000-22,000 years ago and earliest inferred expansion in northwest Africa, could coincide with the flourishing of the Iberomaurusian industry, whilst U6b and M1b1 appeared at the time of the Capsian culture.

Conclusions: Our high-resolution phylogenetic dissection of both haplogroups and coalescent time assessments suggest that the extant main branching pattern of both haplogroups arose and diversified in the mid-later Upper Palaeolithic, with some sub-clades concomitantly with the expansion of the Iberomaurusian industry. Carriers of these maternal lineages have been later absorbed into and diversified further during the spread of Afro-Asiatic languages in North and East Africa.

Figures

Figure 1
Figure 1
Spatial distribution of haplogroup M1 and U6, with languages’ phyla. Frequency maps were obtained using Surfer 8 (Golden Software, Inc.). The Kriging procedure was used and the dataset was congregated with existing ones [29] and updated with the present study, as well as the data in [27,28]. Figure  1a: frequency map for haplogroup M1. Figure  1b: frequency map for haplogroup U6. Red dots indicate the populations geographic locations.
Figure 2
Figure 2
Schematic tree of Haplogroup M1 and U6. The tree, rooted in L3, shows the major sub-haplogroups of M1 and U6. The branching is phylogenetically correct, but the branches length is not accurate.
Figure 3
Figure 3
Bayesian Skyline Plot for Haplogroups M1 and U6. The BSPs show the variation of the Effective Population Size (Ne) through Time for M1 (Figure  3a) and U6 (Figure  3b) based on the full mitochondrial genomes. The axis scales are identical for both plots. For comparison, the median of the second haplogroup is shown in grey, but not the 95% HPD. Overlaid on the plots are the coalescent ages of some relevant sub-haplogroups, with the vertical bars indicating the calculated coalescent ages (using the calculator from [34]) and the horizontal ones their 95% confidence interval.

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