Sheep ideal research subjects, and thus are not a common model organism. They have, however, played an influential role in some fields of science. In particular, the Roslin Institute of Edinburgh, Scotland used sheep for genetics research that produced groundbreaking results. In 1995, two ewes named Megan and Morag were the first mammals cloned from differentiated cells. A year later, a Finnish Dorset sheep named Dolly, dubbed "the world's most famous sheep" in "Scientific American", was the first mammal to be cloned from an adult somatic cell. Following this, Polly and Molly were the first mammals to be simultaneously cloned and
Mammal scheme used, are the [[Primate]]s including the [[ape]]s, [[monkey]]s and [[lemur]]s; the [[Cetartiodactyla]] including [[whale]]s and [[even-toed ungulates]]; and the [[Carnivora]] which includes [[cat]]s, [[dog]]s, [[weasel]]s, [[bear]]s, [[Pinniped|seals]] and allies. According to "[[Mammal Species of the World]]", 5,416 species were identified in 2006. These were grouped into 1,229 [[genus|genera]], 153 [[family (biology)|families]] and 29 orders. In 2008, the [[International Union for Conservation of Nature]] (IUCN) completed a five-year Global Mammal Assessment for its [[IUCN Red List]], which counted 5,488 species. According to a research published in the "[[Journal of Mammalogy]]" in 2018, the number of recognized mammal species is 6,495