The chicken (Gallus gallus, sometimes G. gallus domesticus) is a domesticated fowl. Recent evidence suggests that domestication of the chicken was under way in Vietnam over 10,000 years ago.Sherman, David M. (2002). Tending Animals in the Global Village. Blackwell Publishing. 46. ISBN 0683180517. Until this discovery, conventional wisdom held that the chicken was domesticated in India.Sherman, David M. (2002). Tending Animals in the Global Village. Blackwell Publishing. 46. ISBN 0683180517. From India the domesticated fowl made its way to Persia. From the Persianized kingdom of Lydia in western Asia Minor, domestic fowl were imported to Greece perhaps as late as the fifth century BCE. Fowl had been known in Egypt since the 18th Dynasty, the "bird that lays every day" having come to Egypt, according to the annals of Tutmose III, as tribute from from the land between Syria and Shinar, that is Babylonia. Fowl make no appearance in the Old Testament.

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.

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, consuming both their meat and their eggs.

Terminology

In the U.S.A., Canada and Australia, adult male chickens are known as cocks. 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 sexes. 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 public house 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

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.