Reshaping the Hexagone: the genetic landscape of modern France

Abstract

Unlike other European countries, Metropolitan France is surprisingly understudied. In this work, we combined newly genotyped samples from various zones in France with publicly available data and applied both allele frequency and haplotype-based methods in order to describe the internal structure of this country, taking advantage of the Human Origins SNP array, specifically designed for human population genetics studies. We found out that French Basques are genetically distinct from all other populations in the Hexagone and that the populations from southwest France (namely the Franco-Cantabrian region) are intermediate between Basques and other populations. Moreover, Bretons slightly separated from the rest of the groups and a link with the historical gene flow from the British Isles has been found. Results from the allele frequency analyses point to a general background that appears to be a mixture of two components, one closer to Southern Italy and the other to Ireland. This combination may be the result of a contact happened in two different moments: in the Early Neolithic, and then Ireland would be a proxy for the continental pathway for the Neolithic wave of advance and South Italy for the coastal penetration, or the Iron Age, when the Celtic and the Mediterranean worlds met in France. On the other hand, results from the haplotype-based methods describe a more structured landscape, highlighting the presence of areas characterized by differential links with the neighboring populations, possibly reflecting a more recent history.