The domestication of animals for agricultural purposes dates back to the beginning of the Neolithic period, 9,000 years ago. Early agriculturalists in the Fertile Crescent of the Near East began breeding goats first, then sheep, pigs, and cattle. The stimulus for this advance was probably global warming at the end of the Ice Age, which caused drought in the Near East and forced people to congregate around reliable sources of water. The subsequent increase in population density strained the ability of hunting and gathering to meet the demand for food. Herding animals provided a reliable source of protein-rich food during times of scarcity.
A domestic animal is characterized by several attributes. First, it is bred in captivity for economic profit. Second, humans control its breeding, territory organization, and food supply. Animals bred in captivity tend to have different anatomies and behavior from their wild ancestors. Stress and dependence on humans causes hormonal imbalances and disrupts growth in different parts of the organism. Captive breeding exaggerates these effects, leading to the retention of juvenile characteristics, such as submissive behavior, a smaller body, fat deposition under the skin, shortening of the jaws, and smaller teeth and brain. Domestic animals also tend to appear quite different from their wild ancestors, as animal breeders selected them for a variety of idiosyncratic traits in order to identify them easily as property.
The first animal species to become domesticated was the dog (Canis familiarus ), occurring more than 12,000 years ago in west Asia. Modern-day mastiffs and greyhounds have changed little from their ancestors 4,000 years ago in Egypt and Asia. Each of the more than 400 breeds of dog is the same species. Many experts think dogs descended from the wolf (Canis lupus ). Other researchers suggest that the domestic dog may have descended from a now extinct wild dog. In either case, breeders selected dogs to look different from their ancestors by favoring those with black, white, or spotted coats, long ears, and curled tails. Dogs possess many juvenile characteristics of wolves, including submissive behavior, short jaws, and smaller brains.
Some believe that dogs descended from wolves and that dogs were easily domesticated because of the similarity between wolves' and humans' social behavior. Both species are acutely aware of social hierarchies, making group living more organized and complex than in any other species. When wolves began to scavenge around human settlements, people adopted pups to serve as guards and hunting companions. The human-raised wolves adapted well to human society and likely treated their human companions as if they were a wolf pack. Eventually, humans started to control the breeding of these proto-domestic wolves and the evolution of Canis familiarus began.
Livestock were the next species to be domesticated. Archaeological evidence of domestic sheep and goats in the Jordan Valley dates back to 7,000 B. C. E. Sheep were domesticated from the Asiatic moufflon (Ovis orientalis ), a grass grazer found in hills and foothills. Domestic goats were derived from the bezoar goat (Capra aegagrus ), a hardy browser found in mountainous terrain. Both species were relatively easy to breed in captivity because they were social and adapted to harsh environmental conditions.
Domestic humpless cattle.
Domestic humpless cattle (Bos taurus ) appear in the archaeological record 6,000 years ago in Egypt and Mesopotamia. Their ancestor was the wild ox (Bos primigenius ), a browsing and grazing ruminant in forests and scrub, now extinct. They provided a multitude of uses, including labor, milk, meat, bone, and tallow (for burning). Domestic humped cattle (Bos indicus ) were domesticated independently in Southeast Asia. The domestic yak, water buffalo, and mithan were each domesticated independently from a different bovine species.
Pigs were domesticated from the wild boar (Sus scrofa ) around the same time as cattle. They resemble dogs and humans more than other livestock in several ways. Pigs enjoy body contact with other family members and build nests and beds. They are physically weak at birth, requiring significant parental investment. These similarities may underlie the variation in cultural attitudes toward pigs as agricultural products. Whereas Muslims, Hindus, and some Christians traditionally considered pigs taboo as a source of protein, the Chinese bred both pigs and dogs specifically for their meat.
Horses were domesticated in the third millennium B. C. E. in Russia and western Asia from the wild horse (Equus ferus ). In early 2001, scientists from the University of California, Los Angeles, and three Swedish universities published research indicating that the domestic horse was so genetically diverse, it could not have originated at one place. Mitochondrial DNA, which is genetically transmitted from mother to children, indicated several different matrilineal (female-based) lines. Based on this finding, the researchers suggested that wild horses were tamed independently in several different parts of the world. The "idea" of domesticating horses may have originated in one place, probably central Asia, but various cultures captured and tamed their own horses.
Horses are grass grazers, making them especially well suited to dry plains. At first they were used for food, then as vehicles for travel. Their ability to carry people had an enormous impact on human economies by speeding travel and transport and was probably a necessary step in the development of civilization.
Domestic cats are an exception to the rule of domestication. Feral cats (Felis silvestris ) helped rid rats and mice from stored grains once agriculture became widespread. Because cats are territorial, nocturnal carnivores, controlled breeding was exceptionally difficult. Consequently, there are relatively few cat breeds even after thousands of years of domestication, and those that exist are not much different from their wild ancestor or each other. The weakness of the effects of domestication on cats has made it difficult to determine when or where they were domesticated, but archaeological evidence indicates that ancient Egyptians kept cats as pets by 1000 B. C. E.
see also Animal Rights; Bioethics; Farming; Hunter-Gatherers.
Brian R. West
Clutton-Brock, Juliet. Domesticated Animals from Early Times. Austin: University of Texas Press, 1981.
Darwin, Charles. The Variation of Animals and Plants Under Domestication. New York: New York University Press, 1988.