Sheeps are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Although the name "sheep" applies to many species, in everyday usage it almost always refers to Ovis aries. Domestic sheep are the most numerous species in their genus, numbering a little over 1 billion, and are most likely descended from the wild mouflon of Europe and Asia.