x̄ - > History of chicken

The chicken is a domesticated bird, with attributes of wild species such as the red and grey junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adult male bird, and a younger male may be called a cockerel. A male that has been castrated is a capon. An adult female bird is called a hen and a sexually immature female is called a pullet. Originally raised for cockfighting or for special ceremonies, chickens were not kept for food until the Hellenistic period. Humans now keep chickens primarily as a source of food and as pets. Chickens are one of the most common and widespread domestic animals, with a total population of 23.7 billion up from more than 19 billion in 2011. There are more chickens in the world than any other bird, but the clade found in the Americas, Europe, the Middle East, and Africa originated from the Indian subcontinent. From ancient India, the chicken spread to Lydia in western Asia Minor, and to Greece by the 5th century BC. Fowl have been known in Egypt since the mid-15th century BC, with the "bird that gives birth every day" having come from the land between Syria and Shinar, Babylonia, according to the annals of Thutmose III. Terminology An adult male is called a 'cock' or 'rooster' and an adult female is called a 'hen'. Other terms are: "Biddy:' a newly hatched chicken "Capon:' a castrated or neutered male chicken 'Chick:' a young chicken "Chook': a chicken "Cockerel:' a young male chicken less than a year old "Pullet:' a young female chicken less than a year old. In the poultry industry, a pullet is a sexually immature chicken less than 22 weeks of age. "Yardbird:' a chicken "Chicken" was originally a term only for an immature, or at least young, bird. However, thanks to its usage on restaurant menus, it has now become the most common term for subspecies in general, especially in American English. In older sources, 'chicken' as a species was typically referred to as 'common fowl' or 'domestic fowl'. "Chicken' may also mean a 'chick'. Etymology According to Merriam-Webster, the term "rooster" originated in the mid- or late 18th century as a euphemism to avoid the sexual connotation of the original English "cock", and is widely used throughout North America. "Roosting" is the action of perching aloft to sleep at night. General biology and habitat Chickens are omnivores. In the wild, they often scratch at the soil to search for seeds, insects, and even animals as large as lizards, small snakes, or sometimes young mice. The average chicken may live for 5-10 years, depending on the breed. The world's oldest known chicken lived 16 years according to Guinness World Records. Roosters can usually be differentiated from hens by their striking plumage of long flowing tails and shiny, pointed feathers on their necks and backs, which are typical of brighter, bolder colors than those of females of the same breed. However, in some breeds, such as the Sebright chicken, the rooster has only slightly pointed neck feathers, the same color as the hens. The identification can be made by looking at the comb, or eventually from the development of spurs on the male's legs. Adult chickens have a fleshy crest on their heads called a comb or cockscomb, and hanging flaps of skin on either side under their beaks called wattles. Collectively, these and other fleshy protuberances on the head and throat are called caruncles. Both the adult male and female have wattles and combs, but in most breeds, these are more prominent in males. A 'muff' or 'beard' is a mutation found in several chicken breeds which causes extra feathering under the chicken's face, giving the appearance of a beard. Domestic chickens are not capable of long-distance flight, although lighter chickens are generally capable of flying for short distances, such as over fences or into trees. Chickens may occasionally fly briefly to explore their surroundings but generally do so only to flee perceived danger. Behavior Social behavior Chickens are gregarious birds and live together in flocks. They have a communal approach to the incubation of eggs and raising of young. Individual chickens in a flock will dominate others, establishing a "pecking order", with dominant individuals having priority for food access and nesting locations. Removing hens or roosters from a flock causes a temporary disruption to this social order until a new pecking order is established. Adding hens, especially younger birds, to an existing flock can lead to fighting and injury. When a rooster finds food, he may call other chickens to eat first. He does this by clucking in a high pitch as well as picking up and dropping the food. This behavior may also be observed in mother hens to call their chicks and encourage them to eat. A rooster's crowing is a loud and sometimes shrill call and sends a territorial signal to other roosters. However, roosters may also crow in response to sudden disturbances within their surroundings. Hens cluck loudly after laying an egg, and also to call their chicks. Chickens also give different warning calls when they sense a predator approaching from the air or on the ground. Crowing Roosters almost always start crowing before four months of age. Although it is possible for a hen to crow as well, crowing is one of the clearest signs of being a rooster. Rooster crowing contests, also known as crowing contests, are a traditional sport in several countries, such as Germany, the Netherlands, Belgium, the United States, Indonesia, and Japan. The oldest contests are held with longcrowers. Depending on the breed, either the duration of the crowing or the times the rooster crows within a certain time is measured. Courtship To initiate courting, some roosters may dance in a circle around or near a hen, often lowering the wing which is closest to the hen. The dance triggers a response in the hen Nesting and laying behavior Hens will often try to lay in nests that already contain eggs and have been known to move eggs from neighboring nests into their own. The result of this behavior is that a flock will use only a few preferred locations, rather than having a different nest for every bird. Hens will often express a preference to lie in the same location. It is not unknown for two hens to try to share the same nest at the same time. If the nest is small, or one of the hens is particularly determined, this may result in chickens trying to lay on top of each other. There is evidence that individual hens prefer to be either solitary or gregarious nesters. Broodiness Under natural conditions, most birds lay only until a clutch is complete, and they will then incubate all the eggs. Hens are then said to "go broody". The broody hen will stop laying and instead will focus on the incubation of the eggs. She will "sit" or "set" on the nest, fluff up or pecking in defense if disturbed or removed. The hen will rarely leave the nest to eat, drink, or dust-bathe. While brooding, the hen maintains the nest at a constant temperature and humidity, as well as turning the eggs regularly during the first part of the incubation. To stimulate broodiness, owners may place several artificial eggs in the nest. To discourage it, they may place the hen in an elevated cage with an open wire floor. Breeds artificially developed for egg production rarely go broody, and those that do often stop part-way through the incubation. However, other breeds, such as the Cochin, Cornish, and Silkie, do regularly go broody, and make excellent mothers, not only for chicken eggs but also for those of other species — even those with much smaller or larger eggs and different incubation periods, such as quail, pheasants, ducks, turkeys, or geese. Hatching and early life Fertile chicken eggs hatch at the end of the incubation period, about 21 days. Hens fiercely guard their chicks and brood them when necessary to keep them warm, at first often returning to the nest at night. She leads them to food and water and will call them toward edible items, but seldom feeds them directly. She continues to care for them until they are several weeks old. Defensive behavior Chickens may occasionally gang up on a weak or inexperienced predator. At least one credible report exists of a young fox killed by hens. A group of hens has been recorded attacking a hawk that had entered their coop. If a chicken is threatened by predators, stress, or is sick, there is a chance that it will puff up its feathers. As with birds in general, reproduction is controlled by a neuroendocrine system, the Gonadotropin-Releasing Hormone-I neurons in the hypothalamus. Locally to the reproductive system itself, reproductive hormones such as estrogen, progesterone, gonadotropins initiate and maintain sexual maturation changes. Over time there is reproductive decline, thought to be due to GnRH-I-N decline. Because there is significant inter-individual variability in egg-producing duration, it is believed to be possible to breed for a further extended useful lifetime in egg-layers. Embryology Chicken embryos have long been used as model systems to study developing embryos. Large numbers of embryos can be provided by commercial chicken farmers who sell fertilized eggs which can be easily opened and used to observe the developing embryo. Equally important, embryologists can carry out experiments on such embryos, close the egg again and study the effect later on. For instance, many important discoveries in the area of limb development have been made using chicken embryos, such as the discovery of the apical ectodermal ridge and the zone of polarizing activity by John W. Saunders. In 2006, scientists researching the ancestry of birds "turned on" a chicken recessive gene, talpid2, and found that the embryo jaws initiated the formation of teeth, like those found in ancient bird fossils. John Fallon, the overseer of the project, stated that chickens have"...retained the ability to make teeth, under certain conditions...." Genetics and genomics Given its eminent role in farming, meat production, but also research, the house chicken was the first bird genome to be sequenced. At 1.21 Gb, the chicken genome is considerably smaller than other vertebrate genomes, such as the human genome. The final gene set contained 26,640 genes, with a total of 19,119 protein-coding genes in annotation release 103, a similar number of protein-coding genes as in the human genome. Physiology Populations of chickens from high-altitude regions like Tibet have special physiological adaptations that result in a higher hatching rate in low oxygen environments. When eggs are placed in a hypoxic environment, chicken embryos from these populations express much more hemoglobin than embryos from other chicken populations. This hemoglobin also has a greater affinity for oxygen, allowing hemoglobin to bind to oxygen more readily. Pinopsins were originally discovered in the chicken pineal gland. Immunology Although all avians appear to have lost TLR9, artificial immunity against bacterial pathogens has been induced in neonatal chicks by Taghavi et al 2008 using tailored oligodeoxynucleotides. Breeding Origins Galliformes, the order of bird that chickens belong to, is directly linked to the survival of birds when all other dinosaurs went extinct. Water or ground-dwelling fowl, similar to modern partridges, survived the Cretaceous-Paleogene extinction event that killed all tree-dwelling birds and dinosaurs. Some of these evolved into the modern Galliformes, of which domesticated chickens are the main model. They are descended primarily from the red junglefowl and are scientifically classified as the same species. As such, domesticated chickens can and do freely interbreed with populations of the red junglefowl. a gene for yellow skin, for instance, was incorporated into domestic birds through hybridization with the grey junglefowl. In a study published in 2020, it was found that chickens shared between 71% - 79% of their genome with red junglefowl, with the period of domestication dated 8,000 years ago. The red junglefowl, known as the bamboo fowl in many Southeast Asian languages, is well adapted to take advantage of the vast quantities of seed produced during the end of the multi-decade bamboo seeding cycle, to boost its own reproduction. In domesticating the chicken, humans took advantage of this predisposition for prolific reproduction of the red junglefowl when exposed to large amounts of food. Exactly when and where the chicken was domesticated remains a controversial issue. Genomic studies estimate that the chicken was domesticated 8,000 years ago A landmark 2020 Nature study that fully sequenced 863 chickens across the world suggests that all domestic chickens originate from a single domestication event of red junglefowl whose present-day distribution is predominantly in southwestern China, northern Thailand, and Myanmar. These domesticated chickens spread across Southeast and South Asia where they interbred with local wild species of junglefowl, forming genetically and geographically distinct groups. Analysis of the most popular commercial breed shows that the White Leghorn breed possesses a mosaic of divergent ancestries inherited from subspecies of the red junglefowl. Middle Eastern chicken remains to go back to a little earlier than 2000 BC in Syria; chickens went southward only in the 1st millennium BC. They reached Egypt for purposes of cockfighting about 1400 BC and became widely bred only in Ptolemaic Egypt. Phoenicians spread chickens along the Mediterranean coasts as far as Iberia. During the Hellenistic period, in the Southern Levant, chickens began to be widely domesticated for food. Breeding increased under the Roman Empire and was reduced in the Middle Ages. Three possible routes of introduction into Africa around the early first millennium AD could have been through the Egyptian Nile Valley, the East Africa Roman-Greek or Indian trade, or from Carthage and the Berbers, across the Sahara. The earliest known remains are from Mali, Nubia, East Coast, and South Africa and date back to the middle of the first millennium AD. These results appeared to confirm that the chickens came from Polynesia and that there were transpacific contacts between Polynesia and South America before Columbus's arrival in the Americas. However, a later report looking at the same specimens concluded: A published, apparently pre-Columbian, Chilean specimen and six pre-European Polynesian specimens also cluster with the same European/Indian subcontinental/Southeast Asian sequences, providing no support for a Polynesian introduction of chickens to South America. In contrast, sequences from two archaeological sites on the Easter Island group with an uncommon haplogroup from Indonesia, Japan, and China may represent a genetic signature of an early Polynesian dispersal. Modeling of the potential marine carbon contribution to the Chilean archaeological specimen casts further doubt on claims for pre-Columbian chickens, and definitive proof will require further analyses of ancient DNA sequences and the radiocarbon and stable isotope data from archaeological excavations within both Chile and Polynesia. The debate for and against a Polynesian origin for South American chickens continued with this 2014 paper and subsequent responses in PNAS. Use by humans Farming More than 50 billion chickens have been reared annually as a source of meat and eggs. In the United States alone, more than 8 billion chickens are slaughtered each year for meat, and more than 300 million chickens are reared for egg production. The vast majority of poultry is raised in factory farms. According to the Worldwatch Institute, 74 percent of the world's poultry meat and 68 percent of eggs are produced this way. An alternative to intensive poultry farming is free-range farming. Friction between these two main methods has led to long-term issues of ethical consumerism. Opponents of intensive farming argue that it harms the environment, creates human health risks, and is inhumane. Advocates of intensive farming say that locates of intensive farming say that their highly efficient systems save food resources owing to increased productivity and that the animals are looked after in state-of-the-art environmentally controlled facilities. Reared for meat Chickens farmed for meat are called broilers. Chickens will naturally live for six or more years, but broiler breeds typically take less than six weeks to reach slaughter size. A free-range or organic broiler will usually be slaughtered at about 14 weeks of age. Reared for eggs Chickens farmed primarily for eggs are called layer hens. In total, the UK alone consumes more than 34 million eggs per day. Some hen breeds can produce over 300 eggs per year, with the highest authenticated rate of egg-laying being 371 eggs in 364 days". After 12 months of laying, the commercial hen's egg-laying ability starts to decline to the point where the flock is commercially unviable. Hens, particularly from battery cage systems, are sometimes infirm or have lost a significant amount of their feathers, and their life expectancy has been reduced from around seven years to less than two years. In the UK and Europe, laying hens are then slaughtered and used in processed foods or sold as "soup hens". or sufficiently long to cause a body eight incubation can successfully occur artificially in machines that provide the correct, controlled environment for the developing chick. The average incubation period for chickens is 21 days but may depend on the temperature and humidity in the incubator. Temperature regulation is the most critical factor for a successful hatch. Variations of more than 1 °C from the optimum temperature will reduce hatch rates. Humidity is also important because the rate at which eggs lose water by evaporation depends on the ambient relative humidity. Evaporation can be assessed by candling, to view the size of the air sac, or by measuring weight loss. Relative humidity should be increased to around 70% in the last three days of incubation to keep the membrane around the hatching chick from drying out after the chick cracks the shell. Lower humidity is usual in the first 18 days to ensure adequate evaporation. The position of the eggs in the incubator can also influence hatch rates. For best results, eggs should be placed with the pointed ends down and turned regularly until one to three days before hatching. If the eggs aren't turned, the embryo inside may stick to the shell and may hatch with physical defects. Adequate ventilation is necessary to provide the embryo with oxygen. Older eggs require increased ventilation. Many commercial incubators are industrial-sized with shelves holding tens of thousands of eggs at a time, with rotation of the eggs a fully automated process. Home incubators are boxes holding from 6 to 75 eggs; they are usually electrically powered, but in the past, some were heated with an oil or paraffin lamp. Diseases and ailments Chickens are susceptible to several parasites, including lice, mites, ticks, fleas, and intestinal worms, as well as other diseases. Despite the name, they are not affected by chickenpox, which is generally restricted to humans. Chickens can carry and transmit salmonella in their dander and feces. In the United States, the Centers for Disease Control and Prevention advise against bringing them indoors or letting small children handle them. Some of the diseases that can affect chickens are shown below: History An early domestication of chickens in Southeast Asia is probable since the word for domestic chicken is part of the reconstructed Proto-Austronesian language. Chickens, together with dogs and pigs, were the domestic animals of the Lapita culture, the first Neolithic culture of Oceania. The first pictures of chickens in Europe are found on Corinthian pottery of the 7th century BC. Chickens were spread by Polynesian seafarers and reached Easter Island in the 12th century AD, where they were the only domestic animal, with the possible exception of the Polynesian rat. They were housed in extremely solid chicken coops built from stone, which was first reported as such to Linton Palmer in 1868, who also "expressed his doubts about this". In culture, The mythological basilisk or cockatrice is depicted as a reptile-like creature with the upper body of a rooster. Abraxas, a figure in Gnosticism, is portrayed in a similar fashion as well.