To examine the evolution of sheep, it is key to go back to where sheep were first mentioned in the history of livestock and agricultural science. “Domestication of animals and plants has played a major role in human history” (Fariello, 2014). Sheep are known for their resilient nature and their ability to easily adapt to ever changing environments and diets, which was one of the primary reasons they were domesticated early on in history (Fariello, 2014). In Egypt around 3000 B.C. it is recorded where herdsmen started to domesticate the animals (Putnam, 1991). Between the time period of 490 B.C. and 475 A.D., sheep were used for religious sacrificial purposes as well as being a source of wool, clothing, and meat (Putnam, 1991).
To clearly illustrate sheep evolution, a full look into the species genetics, traits, and reproduction process is foundational. “Research shows that changes in non-coding DNA are drivers of evolutionary change” (Grandin and Deesing, 2014). Therefore a parallel relationship exists between genetics and domestication. Still there are wild species of sheep found in the world today (“Sheep”, 2018). Yet through the ages as wild sheep were exposed to man consequently, “some combination of genetic changes occurring over generations and environmentally induced development events recurring during each generation” have led to the domesticated sheep types we have today (Grandin and Deesing, 2014). Domesticated sheep are comprised of several various types which includes nearly eight hundred different sheep breeds which have become acclimated to a myriad of physical and geographical habitats (“Sheep”, 2018). “Humans bonded with sheep and goats early on as they settled into agriculturally based communities. Both sheep and goats were domesticated about 10,000 years ago, according to the latest theories” (Simmons and Ekarius, 2009). Sheep which exhibit tamed characteristics, have a heredity structure indicative of the breed they belong to (Kijas, 2009). From sheep’s origin until now, very little genetic variation and differentiation has occurred (Kijas, 2009). A closer genetic examination showed, “Wide scale geographic To examine the evolution of sheep, it is key to go back to where sheep were first mentioned in the history of livestock and agricultural science. “Domestication of animals and plants has played a major role in human history” (Fariello, 2014). Sheep are known for their resilient nature and their ability to easily adapt to ever changing environments and diets, which was one of the primary reasons they were domesticated early on in history (Fariello, 2014). In Egypt around 3000 B.C. it is recorded where herdsmen started to domesticate the animals (Putnam, 1991). Between the time period of 490 B.C. and 475 A.D., sheep were used for religious sacrificial purposes as well as being a source of wool, clothing, and meat (Putnam, 1991).
To clearly illustrate sheep evolution, a full look into the species genetics, traits, and reproduction process is foundational. “Research shows that changes in non-coding DNA are drivers of evolutionary change” (Grandin and Deesing, 2014). Therefore a parallel relationship exists between genetics and domestication. Still there are wild species of sheep found in the world today (“Sheep”, 2018). Yet through the ages as wild sheep were exposed to man consequently, “some combination of genetic changes occurring over generations and environmentally induced development events recurring during each generation” have led to the domesticated sheep types we have today (Grandin and Deesing, 2014). Domesticated sheep, also distribution patterns of endogenous retrovirus insertion site polymorphisms suggested that there were two major waves of sheep migrations: the spread of primitive domestic sheep, presumably from the center of animal domestication, was followed and replaced by the second wave of sheep migration from Southwest Asia with improved traits around 5000 years BP” (Demirci, 2013). In addition Demirci’s genetic research findings concluded, “that the domestic sheep may be the products of two maternally distinct ancestral Ovis gmelinii populations” (2013). All domestic sheep breed variations descended from their wild sheep ancestors which at one time freely roamed the land (Demirci, 2013). Today domesticated sheep can be found in almost every country in the world, and are “more widely distributed than any other species of domestic animal” (“Sheep”, 2018).
According to Simmons and Ekarius, historically “Biologists believe that modern sheep are descended primarily from the wild Mouflon sheep of western Asia, although other wild sheep (for instance, the Urial of central Asia) may have been mixed in since domestication took place” (2009). History has recorded according to Demerci’s research “that wild animals or animals in their early domestication stages have been transported by hunter-gatherers over long distances or even by sea, for instance from the mainland to Cyprus as early as around 12,000 years BP” (2013). In Today’s Science article entitled “Sheep” it lists the following non-domesticated, wild sheep species which still inhabit various regions of the world as being: “the bighorn sheep (O. canadensis) in western North America; Dall's sheep (O. dalli) in northern Canada and Alaska; the mouflon (O. musimon) in Mediterranean countries; the Asian mouflon (O. orientalis) in western Asia; the urial (O. vignei) in Afghanistan and Pakistan; and the argali (O. ammon) in eastern Asia” (2018).
Research clearly shows as a result of domestic sheep being introduced into the environments which were already inhabited by wild sheep, it resulted in the population numbers of wild sheep to decrease and accordingly the genetic diversity of the entire species became less and less (Demerci, 2013). The population of wild sheep are now considered an endangered species throughout the world (Simmons and Ekarius, 2009). Furthermore, the heredity traits commonly associated with wild sheep, from the massive horns which curl along with the heavy outer wool coats, these wild breed characteristics are nearly obsolete in domestic breeds due to the heredity disintegration (Simmons and Ekarius, 2009).
In looking to the future, sheep continue to hold a significant place in animal agriculture. “Sheep are extremely well adapted to conservation agriculture, and a strong animal agriculture is essential to resource conservation and is complementary with good conservation practices” (Putnam, 1991). Specialization breeding and sheep production practices continue to focus on the end product desired such as wool for clothing, or milk and meat for consumption (Kijas, 2009). With the scientifically famous domesticated sheep known as Dolly being the first mammal to be successfully cloned from the adult cell of another sheep; undoubtedly the future still holds new scientific animal research data yet to be discovered (“Cloning Dolly the Sheep”, 2018). Not only does the animal research benefit animal science and agriculture, but there have been many notable benefits for humans as a result of animal research studies. For example, “the development of cloning technology has led to new ways to produce medicines and is improving our understanding of development and genetics” (“Cloning Dolly the Sheep”, 2018). In fact, we have already seen what Putman described in his text as the “application of genetic engineering to meet animal health and production challenges” (Putnam, 1991). “Researchers have managed to transfer human genes that produce useful proteins into sheep and cows, so that they can produce, for instance, the blood clotting agent factor IX to treat haemophilia or alpha-1-antitrypsin to treat cystic fibrosis and other lung conditions” (“Cloning Dolly the Sheep”,2018). The scientific discoveries thus far using sheep genes has paved the way for other new human medical interventions and therapies. For instance, “the advances made through cloning animals have led to a potential new therapy to prevent mitochondrial diseases in humans being passed from mother to child” (“Cloning Dolly the Sheep”,2018). Essentially as sheep continue to evolve genetically and in their natural habitat, so shall they also continue evolving in the scientific laboratory. Not only shall future sheep genetic research impact animal production efficiency, but hopefully it will continue to positively benefit humans as well for generation after generation.