Meat is animal tissue, often muscle, that is eaten as food. Humans have hunted and farmed other animals for meat since prehistoric times. The Neolithic Revolution allowed the domestication of animals including chickens, sheep, goats, pigs, horses, and cattle, starting around 11,000 years ago. Since then, selective breeding has enabled farmers to produce meat with the qualities desired by producers and consumers.

Meat is mainly composed of water, protein, and fat. Its quality is affected by many factors, including the genetics and nutritional status of the animal involved. It is edible raw, but is normally eaten cooked, such as by stewing or roasting, or processed, such as by smoking or salting. Bacteria and fungi decompose and spoil unprocessed meat within hours or days.

The consumption of meat, especially red and processed meat, causes health effects including increased risks of cancer, coronary heart disease, and diabetes. Meat production is a major contributor to environmental issues including global warming, pollution, and biodiversity loss, at every scale from local to global.

Meat is important to economies and cultures around the world. Some people choose not to eat meat (vegetarians) for reasons such as ethics, environmental effects, health concerns, or religious dietary rules.

Etymology
The word meat comes from the Old English word mete, meaning food in general. In modern usage, meat means skeletal muscle and associated fat and other tissues, but it may also denote other edible tissues such as offal.[1] Meat is sometimes used in a more restrictive sense to mean the flesh of mammalian species (pigs, cattle, sheep, goats, etc.) raised and prepared for human consumption, to the exclusion of fish, other seafood, insects, poultry, or other animals.[2][3] English has specialized terms for the meat of particular animals, deriving from the Norman conquest of England in 1066: while the animals retained their English names, their meat as brought to the tables of the invaders was named in Norman French. These names came to be used by the entire population.[4]

Meat of... ...is called:[4] Etymology
Pigs Pork Norman French porc (pig)
Cattle Beef Norman French boeuf (cattle)
Sheep Mutton Norman French mouton (sheep)
Calves Veal Norman French veau (calf)
Domesticated birds Poultry Norman French poule (domestic fowl)
Goats Chevon Old French chèvre (goat)
Deer Venison Old French venesoun (meat of large game)
History
Further information: History of agriculture
Domestication
Further information: Domestication
Paleontological evidence suggests that meat constituted a substantial proportion of the diet of the earliest humans. Early hunter-gatherers depended on the organized hunting of large animals such as bison and deer. Animals were domesticated in the Neolithic, enabling the systematic production of meat and the breeding of animals to improve meat production.[5]

Major animal domestications
Event Centre of origin Purpose Date/years ago
Goat, Sheep, Pig, Cow Near East, South Asia Food 11,000–10,000[6]
Chicken East Asia Cockfighting 7,000[7]
Horse Central Asia Draft, riding 5,500[8]
Intensive animal farming
Further information: Intensive animal farming
In the postwar period, governments gave farmers guaranteed prices to increase animal production. The effect was to raise output at the cost of increased inputs such as of animal feed and veterinary medicines, as well as of animal disease and environmental pollution.[9] In 1966, the United States, the United Kingdom and other industrialized nations, began factory farming of beef and dairy cattle and domestic pigs.[10] Intensive animal farming became globalized in the later years of the 20th century, replacing traditional stock rearing in countries around the world.[10] In 1990 intensive animal farming accounted for 30% of world meat production and by 2005, this had risen to 40%.[10]

Selective breeding
Modern agriculture employs techniques such as progeny testing to speed selective breeding, allowing the rapid acquisition of the qualities desired by meat producers.[11] For instance, in the wake of well-publicised health concerns associated with saturated fats in the 1980s, the fat content of United Kingdom beef, pork and lamb fell from 20–26 percent to 4–8 percent within a few decades, due to both selective breeding for leanness and changed methods of butchery.[11] Methods of genetic engineering that could improve the meat-producing qualities of animals are becoming available.[12]

Meat production continues to be shaped by the demands of customers. The trend towards selling meat in pre-packaged cuts has increased the demand for larger breeds of cattle, better suited to producing such cuts.[13] Animals not previously exploited for their meat are now being farmed, including mammals such as antelope, zebra, water buffalo and camel,[14] as well as non-mammals, such as crocodile, emu and ostrich.[15] Organic farming supports an increasing demand for meat produced to that standard.[16]

A shoulder of lamb
A shoulder of lamb

A Hereford bull, a breed of beef cattle
A Hereford bull, a breed of beef cattle

Dog meat on sale, South Korea
Dog meat on sale, South Korea

Supermarket meat, North America
Supermarket meat, North America
Animal growth and development
Several factors affect the growth and development of meat.

Genetics
Trait Heritability[17]
Reproductive efficiency 2–10%
Meat quality 15–30%
Growth 20–40%
Muscle/fat ratio 40–60%
Some economically important traits in meat animals are heritable to some degree, and can thus be selected for by animal breeding. In cattle, certain growth features are controlled by recessive genes which have not so far been controlled, complicating breeding.[18] One such trait is dwarfism; another is the doppelender or "double muscling" condition, which causes muscle hypertrophy and thereby increases the animal's commercial value.[18] Genetic analysis continues to reveal the genetic mechanisms that control numerous aspects of the endocrine system and, through it, meat growth and quality.[19]

Genetic engineering techniques can shorten breeding programs significantly because they allow for the identification and isolation of genes coding for desired traits, and for the reincorporation of these genes into the animal genome.[20] To enable such manipulation, the genomes of many animals are being mapped.[20] Some research has already seen commercial application. For instance, a recombinant bacterium has been developed which improves the digestion of grass in the rumen of cattle, and some specific features of muscle fibres have been genetically altered.[21] Experimental reproductive cloning of commercially important meat animals such as sheep, pig or cattle has been successful. Multiple asexual reproduction of animals bearing desirable traits is anticipated.[21]

Environment
Heat regulation in livestock is of economic significance, as mammals attempt to maintain a constant optimal body temperature. Low temperatures tend to prolong animal development and high temperatures tend to delay it.[21] Depending on their size, body shape and insulation through tissue and fur, some animals have a relatively narrow zone of temperature tolerance and others (e.g. cattle) a broad one.[22] Static magnetic fields, for reasons still unknown, also ♥♥♥♥♥♥ animal development.[22]

Animal nutrition
The quality and quantity of usable meat depends on the animal's plane of nutrition, i.e., whether it is over- or underfed. Scientists disagree about how exactly the plane of nutrition influences carcass composition.[23]

The composition of the diet, especially the amount of protein provided, is also an important factor regulating animal growth.[24] Ruminants, which may digest cellulose, are better adapted to poor-quality diets, but their ruminal microorganisms degrade high-quality protein if supplied in excess.[25] Because producing