Abstract
The current human mitochondrial (mtDNA) phylogeny does not equally represent all human populations but is biased in favour of representatives originally from north and central Europe. This especially affects the phylogeny of some uncommon West Eurasian haplogroups, including I and W, whose southern European and Near Eastern components are very poorly represented, suggesting that extensive hidden phylogenetic substructure remains to be uncovered. This study expanded and re-analysed the available datasets of I and W complete mtDNA genomes, reaching a comprehensive 419 mitogenomes, and searched for precise correlations between the ages and geographical distributions of their numerous newly identified subclades with events of human dispersal which contributed to the genetic formation of modern Europeans. Our results showed that haplogroups I (within N1a1b) and W originated in the Near East during the Last Glacial Maximum or pre-warming period (the period of gradual warming between the end of the LGM, ∼19 ky ago, and the beginning of the first main warming phase, ∼15 ky ago) and, like the much more common haplogroups J and T, may have been involved in Late Glacial expansions starting from the Near East. Thus our data contribute to a better definition of the Late and postglacial re-peopling of Europe, providing further evidence for the scenario that major population expansions started after the Last Glacial Maximum but before Neolithic times, but also evidencing traces of diffusion events in several I and W subclades dating to the European Neolithic and restricted to Europe.
Highlights
Evidence from mitochondrial DNA suggests that a southern dispersal from the Horn of Africa along the Indian Ocean coasts might have brought anatomically modern humans out of Africa,60–70 thousand years ago [1,2,3] archaeological evidence from Southern Arabian and Indian sites has led some to propose an even earlier exit along the southern route [4,5,6]. ,15–25 ky later, during the Early Upper Palaeolithic, the first modern Europeans arrived from the Levant [7,8,9,10]
Palaeolithic events include both the first entry to the continent and the re-settlement from southern refugia after the Last Glacial Maximum (LGM), starting from,19 kya, while Neolithic phases primarily coincide with the spread of agriculture and pastoralism that began in the Near East,10 kya and progressively reached the Balkans, Central Europe, the West Mediterranean, and the north, argued to have been accompanied by substantial increases in population size [11]
Our results showed that haplogroups N1a1b1, I and W most probably originated in the Near East during the Last Glacial Maximum or pre-warming period and, like J and T, may have been involved in Late Glacial expansions starting from the Near East
Summary
Evidence from mitochondrial DNA (mtDNA) suggests that a southern dispersal from the Horn of Africa along the Indian Ocean coasts might have brought anatomically modern humans out of Africa ,60–70 thousand years ago (kya) [1,2,3] archaeological evidence from Southern Arabian and Indian sites has led some to propose an even earlier exit along the southern route [4,5,6]. ,15–25 ky later, during the Early Upper Palaeolithic, the first modern Europeans arrived from the Levant [7,8,9,10]. The analysis of mitochondrial DNA variation based on the phylogeographic analysis of the mtDNA control-region sequence and coding-region RFLP markers [14,15,16] turned the tide, pointing to a more significant contribution from the indigenous hunter-gatherers estimated to at least ,80%. This suggested that only small groups of Neolithic people settled Europe and a wide-scale adoption of agricultural technology by indigenous Mesolithic/Palaeolithic populations occurred [3]
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