Abstract
BackgroundThe out of Africa hypothesis has gained generalized consensus. However, many specific questions remain unsettled. To know whether the two M and N macrohaplogroups that colonized Eurasia were already present in Africa before the exit is puzzling. It has been proposed that the east African clade M1 supports a single origin of haplogroup M in Africa. To test the validity of that hypothesis, the phylogeographic analysis of 13 complete mitochondrial DNA (mtDNA) sequences and 261 partial sequences belonging to haplogroup M1 was carried out.ResultsThe coalescence age of the African haplogroup M1 is younger than those for other M Asiatic clades. In contradiction to the hypothesis of an eastern Africa origin for modern human expansions out of Africa, the most ancestral M1 lineages have been found in Northwest Africa and in the Near East, instead of in East Africa. The M1 geographic distribution and the relative ages of its different subclades clearly correlate with those of haplogroup U6, for which an Eurasian ancestor has been demonstrated.ConclusionThis study provides evidence that M1, or its ancestor, had an Asiatic origin. The earliest M1 expansion into Africa occurred in northwestern instead of eastern areas; this early spread reached the Iberian Peninsula even affecting the Basques. The majority of the M1a lineages found outside and inside Africa had a more recent eastern Africa origin. Both western and eastern M1 lineages participated in the Neolithic colonization of the Sahara. The striking parallelism between subclade ages and geographic distribution of M1 and its North African U6 counterpart strongly reinforces this scenario. Finally, a relevant fraction of M1a lineages present today in the European Continent and nearby islands possibly had a Jewish instead of the commonly proposed Arab/Berber maternal ascendance.
Highlights
The out of Africa hypothesis has gained generalized consensus
It is surprising that none of the three M1c complete sequences have an eastern Africa ancestry: one (Jor771) has a Levantine origin and the other two belong to West sub-Saharan Africa (SER558) and West Mediterranean (VAL1881) areas
Later an M1b subclade defined by the non-coding motif 16260–16320 and restricted to East Africans was identified [21]
Summary
The out of Africa hypothesis has gained generalized consensus. many specific questions remain unsettled. The greatest diversity and the deepest phylogenetic branches for both Y-chromosome [2,3] and mtDNA [4,5] have been found in Africa These African lineages have coalescence ages [6,7,8,9] compatible with a recent African origin of modern humans as proposed by fossil [10,11] and archaeological studies [12]. In addition, the founder ages of M and N are very similar, the alternative hypothesis, that M and N founders derived from a single African migration, was favored by several authors [16,19,20,21] Another related disjunctive yet not settled is whether M and N (and its main branch R) arose inside or outside Africa [20]. The alternative hypothesis, that haplogroup M1 could trace a posterior backflow to Africa from Asia, considered by several authors [7,21,23,24] has not yet gained experimental support because, until now, no ancestral M1 lineages have been found outside Africa [21,24,25]
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