The sheep is one of the most successful and widely spread domestic animals. Archaeological evidence traces the first domestic sheep back to the Near East region around 9,000 years ago. It is also known that soon after, the domesticated sheep started to flow out of the centre of origin and spread all over the ancient world following the expansion of agriculture. Throughout time, herders, nature elements and eventually some hybridization with different wild relatives produced a multitude of breeds. However, until the advent of the molecular genetics field, very little was known about the origins of most of those breeds. Two decades after the first genetic studies, we have gathered considerable information on the origins, phylogenetic relationships and patterns of genetic diversity of the sheep across the world. Indeed, the genetic studies confirmed the Near East region as the main centre of origin and also revealed other contributions from other regions. Specifically about the fat-tailed sheep, molecular genetics was also able to link their maternal origin to a specific group. So far, modern sheep have originated from five different maternal origins. Nonetheless, the technological advances of the DNA sequencing techniques are bringing more data that is showing the complexity of the domestication process.