History of Meats
Are Houmans Capable of Consuming Meat
Meat is animal flesh that is eaten as food. Humans are omnivorous, and have hunted and killed animals for meat since prehistoric times. But the advent of civilization allowed the domestication of animals such as sheep, pigs and cattle, and their use in meat production on an industrial scale.
Meat is mainly composed of water and protein, and is usually eaten together with other food. It is edible raw but is normally eaten cooked and seasoned in a variety of ways. Unprocessed, it will spoil within hours or days.
Meat consumption varies worldwide, depending on cultural or religious preferences. Vegetarians choose not to eat meat because of ethical, environmental, religious or health concerns that are associated with meat production and consumption.
Most often, “meat” refers to skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as offal. Conversely, “meat” is sometimes also used in a more restrictive sense – the flesh of mammalian species (pigs, cattle, lambs, etc.) raised and prepared for human consumption, to the exclusion of fish and other seafood, poultry, and other animals.
The word meat comes from the Old English word mete, which referred to food in general. The term is related to mad in Danish, matin Swedish and Norwegian, and matur in Icelandic and Faroese, which also mean ‘food’. The word “mete” also exists in Old Frisian(and to a lesser extent, modern West Frisian) to denote important food, differentiating it from “swiets” (sweets) and “dierfied” (animal feed).
History – History of agriculture
Paleontological evidence suggests that meat constituted a substantial proportion of the diet of even the earliest humans. Earlyhunter-gatherers depended on the organized hunting of large animals such as bison and deer.
The domestication of animals, of which we have evidence dating back to the end of the last glacial period (c. 10,000 years BP), allowed the systematic production of meat and the breeding of animals with a view to improving meat production. The animals which are now the principal sources of meat were domesticated in conjunction with the development of early civilizations:
- Sheep, originating from western Asia, were domesticated with the help of dogs prior to the establishment of settled agriculture, likely as early as the eighth millennium BC. Several breeds of sheep were established in ancient Mesopotamia and Egypt by 3500–3000 BC. Presently, more than 200 sheep breeds exist.
- Cattle were domesticated in Mesopotamia after settled agriculture was established about 5000 BC, and several breeds were established by 2500 BC. Modern domesticated cattle fall into the groups Bos taurus (European cattle) and Bos indicus (zebu), both descended from the now-extinct aurochs. The breeding of beef cattle, cattle optimized for meat production as opposed to animals best suited for draught or dairy purposes, began in the middle of the 18th century.
- Domestic pigs, which are descended from wild boars, are known to have existed about 2500 BC in modern-day Hungary and in Troy; earlier pottery from Jericho and Egypt depicts wild pigs. Pork sausages and hams were of great commercial importance in Greco-Roman times. Pigs continue to be bred intensively as they are being optimized to produce meat best suited for specific meat products.
Other animals are, or have been raised or hunted for their flesh. The type of meat consumed varies much in different cultures, changes over time, and depends on different factors such as the availability of the animals and traditions. The amount and kind of meat consumed also depends on income, country to country and within a given country.
- Horses are commonly eaten in countries such as France Italy, Germany or Japan. Horses (and other large mammals as reindeers) were hunted during the Late Paleolithic in western Europe.
- Dogs are consumed in China, Vietnam, and South Korea. Dogs are also occasionally eaten in the Arctic regions. Historically, dog meat has been consumed in various part of the world, such as Hawaii, Japan, Switzerland and Mexico.
- Cats are consumed in Southern China and Peru.
- Guinea pigs are raised for their flesh in the Andes.
- Whales and dolphins are hunted, partly for their flesh, by aboriginal communities in Japan, Alaska, Siberia, Canada, by the Faroe Islands, Greenland, Iceland, Saint Vincent and the Grenadines and by two small communities in Indonesia.
Modern agriculture employs a number of techniques, such as progeny testing, to make animals evolve rapidly towards having the qualities desired by meat producers. For instance, in the wake of well-publicised health concerns associated with saturated fatsin 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, both due to selective breeding for leanness and changed methods of butchery. Methods of genetic engineering aimed at improving the meat production qualities of animals are now also becoming available.
Even though it is a very old industry, meat production continues to be shaped strongly by the rapidly evolving demands of customers. The trend towards selling meat in pre-packaged cuts has increased the demand for larger breeds of cattle, which are better suited to producing such cuts. Even more animals not previously exploited for their meat are now being farmed, especially the more agile and mobile species, whose muscles tend to be developed better than those of cattle, sheep or pigs. Examples include the various antelope species, the zebra, water buffalo and camel, as well as nonmammals, such as the crocodile, emuand ostrich. Another important trend in contemporary meat production is organic farming which, while providing no organoleptic benefit to meat so produced, meets an increasing demand for organic meat.
Growth and development of meat animals – Agricultural science has identified several factors bearing on the growth and development of meat in animals.
Several economically important traits in meat animals are heritable to some degree (see the table to the right) and can thus be selected for by breeding. In cattle, certain growth features are controlled by recessive genes which have not so far been controlled, complicating breeding. 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. Genetic analysis continues to reveal the genetic mechanisms that control numerous aspects of the endocrine system and, through it, meat growth and quality.
Genetic engineering techniques can shorten breeding programmes 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. To enable such manipulation, research is ongoing (as of 2006) to map the entire genome of sheep, cattle and pigs. 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.
Experimental reproductive cloning of commercially important meat animals such as sheep, pig or cattle has been successful. The multiple asexual reproduction of animals bearing desirable traits can thus be anticipated, although this is not yet practical on a commercial scale.
Heat regulation in livestock is of great economic significance, because mammals attempt to maintain a constant optimal body temperature. Low temperatures tend to prolong animal development and high temperatures tend to retard it. 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. Static magnetic fields, for reasons still unknown, also retard animal development.
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, however, about how exactly the plane of nutrition influences carcase composition.
The composition of the diet, especially the amount of protein provided, is also an important factor regulating animal growth. Ruminants, which may digest cellulose, are better adapted to poor-quality diets, but their ruminal microorganisms degrade high-quality protein if supplied in excess. Because producing high-quality protein animal feed is expensive (see also Environmental impact below), several techniques are employed or experimented with to ensure maximum utilization of protein. These include the treatment of feed with formalin to protect amino acids during their passage through the rumen, the recycling of manure by feeding it back to cattle mixed with feed concentrates, or the partial conversion of petroleum hydrocarbons to protein through microbial action.
In plant feed, environmental factors influence the availability of crucial nutrients or micronutrients, a lack or excess of which can cause a great many ailments. In Australia, for instance, where the soil contains limited phosphate, cattle are being fed additional phosphate to increase the efficiency of beef production. Also in Australia, cattle and sheep in certain areas were often found losing their appetite and dying in the midst of rich pasture; this was at length found to be a result of cobalt deficiency in the soil. Plant toxins are also a risk to grazing animals; for instance, fluoracetate, found in some African and Australian plants, kills by disrupting the cellular metabolism. Certain man-made pollutants such as methylmercury and some pesticide residues present a particular hazard due to their tendency to bioaccumulate in meat, potentially poisoning consumers.
Meat producers may seek to improve the fertility of female animals through the administration of gonadotrophic or ovulation-inducing hormones. In pig production, sow infertility is a common problem, possibly due to excessive fatness. No methods currently exist to augment the fertility of male animals. Artificial insemination is now routinely used to produce animals of the best possible genetic quality, and the efficiency of this method is improved through the administration of hormones that synchronize the ovulation cycles within groups of females.
Growth hormones, particularly anabolic agents such as steroids, are used in some countries to accelerate muscle growth in animals. This practice has given rise to the beef hormone controversy, an international trade dispute. It may also decrease the tenderness of meat, although research on this is inconclusive, and have other effects on the composition of the muscle flesh. Where castration is used to improve control over male animals, its side effects are also counteracted by the administration of hormones.
Sedatives may be administered to animals to counteract stress factors and increase weight gain. The feeding of antibiotics to certain animals has been shown to improve growth rates also. This practice is particularly prevalent in the USA, but has been banned in the EU, partly because it causes antibiotic resistance in pathogenic microorganisms.
Numerous aspects of the biochemical composition of meat vary in complex ways depending on the species, breed, sex, age, plane of nutrition, training and exercise of the animal, as well as on the anatomical location of the musculature involved. Even between animals of the same litter and sex there are considerable differences in such parameters as the percentage of intramuscular fat.
Adult mammalian muscle flesh consists of roughly 75 percent water, 19 percent protein, 2.5 percent intramuscular fat, 1.2 percent carbohydrates and 2.3 percent other soluble non-protein substances. These include nitrogenous compounds, such as amino acids, and inorganic substances such as minerals.
Muscle proteins are either soluble in water (sarcoplasmic proteins, about 11.5 percent of total muscle mass) or in concentrated salt solutions (myofibrillar proteins, about 5.5 percent of mass). There are several hundred sarcoplasmic proteins. Most of them – the glycolytic enzymes – are involved in the glycolytic pathway, i.e., the conversion of stored energy into muscle power. The two most abundant myofibrillar proteins, myosin and actin, are responsible for the muscle’s overall structure. The remaining protein mass consists of connective tissue (collagen and elastin) as well as organelle tissue.
Fat in meat can be either adipose tissue, used by the animal to store energy and consisting of “true fats” (esters of glycerol with fatty acids), or intramuscular fat, which contains considerable quantities of phospholipids and of unsaponifiable constituents such as cholesterol.
Meat can be broadly classified as “red” or “white” depending on the concentration of myoglobin in muscle fibre. When myoglobin is exposed to oxygen, reddish oxymyoglobin develops, making myoglobin-rich meat appear red. The redness of meat depends on species, animal age, and fibre type: Red meat contains more narrow muscle fibres that tend to operate over long periods without rest, while white meat contains more broad fibres that tend to work in short fast bursts.
The meat of adult mammals such as cows, sheep, goats, and horses is generally considered red, while domestic chicken and turkey breast meat is generally considered white (to read more go to the link above).