Following the herd : Population genetics of European sheep in time and space

Abstract: Sheep, which were domesticated in the Fertile Crescent about 10,000-12,000 years ago, have been a key resource for human populations ever since. We, however, know little about how they were domesticated, and what happened to them after their initial expansion from their domestication area into all corners of Eurasia and later Africa and the Americas. In this thesis I use state-of-the-art methods in population genetics and archaeogenetics to try to elucidate how sheep have evolved into the big diversity of modern breeds we see today and what demographic events shaped modern sheep genetic landscape in Europe. We were able to characterize the demographic history of three key locations in Europe for sheep: Iberia, the Baltic region and the Mediterranean islands. Our results confirm that the initial Neolithic expansion into Europe followed two independent routes, through the Danube-Rhine axis in Central Europe and sailing through the Mediterranean, and that mouflons from Corsica and Sardinia descend from this last early domestic sheep. We were also able to identify two independent expansions into Europe of Eastern ancestry, one related with archaic long wool, a phenotype retained by primitive European sheep breeds, and a later one associated with more modern woolly phenotypes. This last expansion, that occurred slightly before or during the Roman period in Iberia, didn’t reached the Baltic region, whose breeds are still to this day displaying primitive phenotypes. Lastly, we were able to describe the phylogeny of modern wild and feral mouflons from the Mediterranean and the Middle East. My thesis highlight the dynamic nature of the demographic history of sheep, and how responsive it has been to human demographic and cultural changes.