Updating the Phylogeography and Temporal Evolution of Mitochondrial DNA Haplogroup U8 with Special Mention to the Basques

Abstract

Mitochondrial DNA phylogenetic and phylogeographic studies have been very useful in reconstructing the history of modern humans. In addition, recent advances in ancient DNA techniques have enabled direct glimpses of the human past. Taking advantage of these possibilities, I carried out a spatiotemporal study of the rare and little-studied mtDNA haplogroup U8. Today, U8, represented by its main branches U8a and U8b, has a wide western Eurasian range but both with average frequencies below 1%. It is known that, in Paleolithic times, U8 reached high frequencies in European hunter-gatherers. However, it is pertinent to precise that only lineages belonging to U8a and U8c, a sister branch of U8b, were detected at that time. In spite of its wide geographic implantation, U8c was extinct after the Last Glacial Maximum, but U8a subsisted until the present day, although it never reached its high Paleolithic frequencies. U8a is detected mainly in northern and western Europe including the Basques, testifying to a minor maternal Paleolithic continuity. In this respect, it is worth mentioning that Basques show more U8-based affinities with continental European than with Mediterranean populations. On the contrary, coalescent ages of the most ancient U8b clades point to a Paleolithic diversification in the Caucasus and the Middle Eastern areas. U8b-derived branches reached eastern Europe since the Mesolithic. Subsequent Neolithic and post-Neolithic expansions widen its ranges in continental Europe and the Mediterranean basin, including northern Africa, albeit always as a minor clade that accompanied other, more representative, mitochondrial lineages.