The chicken (Gallus gallus, sometimes G. gallus domesticus) is a domesticated fowl which is traditionally believed to have descended from the wild Red Junglefowl found in India (species: Gallus Gallus).fowl. Encyclopedia Britannica 2008. However, some genetic research has suggested that the bird likely descended from both Red and the Grey Junglefowl (G. sonneratii). Although hybrids of both wild types usually tend toward sterility, recent genetic work has revealed that the genotype for yellow skin present in the domestic fowl is not present in what is otherwise its closest kin, the Red Junglefowl. It is deemed most likely, then, that the yellow skin trait in domestic birds originated in the Grey Junglefowl.

As the species spread domestication occurred throughout multiple sites in Asia—including India where it was used for cock fighting.Sherman, David M. (2002). Tending Animals in the Global Village. Blackwell Publishing. 46. ISBN 0683180517. From India the domestication of chicken spread throughout Near East, Africa and the Greco-Roman world.

The chicken is one of the most common and widespread domestic animals. With a population of more than 24 billion in 2003, there are more chickens in the world than any other bird. Humans keep chickens primarily as a source of food, with both their meat and their eggs consumed.

Terminology

In the U.S.A., Canada and Australia, adult male chickens are known as roosters; in the UK they are known as cocks.Fact: date=April 2008 Males under a year old are cockerels. Castrated roosters are called capons (though both surgical and chemical castration are now illegal in some parts of the world). Females over a year old are known as hens, and younger females are pullets. In Australia and New Zealand (also sometimes in Britain), there is a useful generic term chook (rhymes with "book") to describe all ages and both genders.. Babies are called chicks, and the meat is called chicken]].

"Chicken" was originally the word only for chicks, and the species as a whole was then called domestic fowl, or just fowl. This use of "chicken" survives in the phrase "Hen and Chickens," sometimes used as a UK pub or theatre name, and to name groups of one large and many small rocks or islands in the sea (see for example Hen and Chicken Islands).

General biology and habitat

[[image:Hen and chicks.JPG Chickens are omnivores. In the wild, they often scratch at the soil to search for seeds, insects and even larger animals such as lizards or young mice.

Chickens in nature may live for five to eleven years depending on the breed. In commercial intensive farming, a meat Chicken generally lives only six weeks before slaughter. A free range or organic meat chicken will usually be slaughtered at about 14 weeks. Hens of special laying breeds may produce as many as 300 eggs a year. After 12 months, the hen's egg-laying ability starts to decline, and commercial laying hens are then slaughtered and used in baby foods, pet foods, pies and other processed foods. The world's oldest chicken, according to the Guinness Book of World Records, died of heart failure when she was 16 years.