Archaeogenetics of Western Europe: the transition from the Mesolithic to the Neolithic

The transition from hunting to farming started in the Fertile Crescent of the Near East, about 12 thousand years ago (kya). During the following millennia, farming spread across Europe largely due to migrations of people from a source in western Anatolia. The aim of this thesis is to investigate and assess the relative contribution of local hunter-gatherers and dispersing farming groups in a region of Western Europe where the archaeological evidence suggests potential complexity. In order to do so, two parallel approaches were carried out: i) the study of human remains from three archaeological sites in Belgium; and ii) a broader phylogeographic analysis of modern mitochondrial DNA sequences belonging to haplogroup HV.

Here I report the first genome-wide analysis of one Mesolithic and 32 Middle to Late Neolithic Belgian individuals. The Mesolithic individual was largely similar to other Western European Mesolithic and Late Palaeolithic samples. However, within the Neolithic group I observed two genetic clusters. The first cluster appears to be the result of an admixture between local Mesolithic hunter-gatherers and Neolithic farmers of Anatolian descent. However, the Mesolithic component was much larger than seen to date in other west European Neolithic samples, with a possible sex bias towards local males carrying Y-chromosome haplogroup I and dispersing females. The second, less numerous genome-wide cluster revealed admixture from a Pontic-Caspian Steppe related population, further indicated by the presence of Y-chromosome R1b-M269.

The phylogeographic analysis of modern mitochondrial haplogroup HV confirmed an Upper Palaeolithic Near Eastern origin. The new findings suggest an early introduction of several HV lineages into the north coast of the Mediterranean from the Late Glacial onwards, which increased during the Neolithic. In particular, the Mediterranean area appears to have served as a reservoir of HV lineages and as a source of later migrations in both the Neolithic and the Bronze Age.