The chicken (Gallus gallus domesticus) is a type of domesticated fowl, a subspecies of the red junglefowl. It is one of the most common and widespread domestic animals, with a population of more than 19 billion as of 2011.[1] Humans keep chickens primarily as a source of food, consuming both their meat and their eggs.

Genetic studies have pointed to multiple maternal origins in Southeast-, East-,[2] and South Asia, but with the clade found in the Americas, Europe, the Middle East and Africa originating in the Indian subcontinent. From India, the domesticated chicken was imported to Lydia in western Asia Minor, and to Greece by the fifth century BC.[3] Fowl had been known in Egypt since the mid-15th century BC, with the “bird that gives birth every day” having come to Egypt from the land between Syria and Shinar, Babylonia, according to the annals of Thutmose III.[4][5][6] The chicken genome has changed less from feathered ancestors eradicated by the Cretaceous–Paleogene extinction event than those of other sequenced avian dinosaurs.[7]


Male red junglefowl.

The domestic chicken is descended primarily from the red junglefowl (Gallus gallus) and is scientifically classified as the same species.[22]As such it can and does freely interbreed with populations of red jungle fowl.[22] Recent genetic analysis has revealed that at least the gene for yellow skin was incorporated into domestic birds through hybridization with the grey junglefowl (G. sonneratii).[23] The traditional poultry farming view is that chickens were first domesticated for cockfighting in Asia, Africa, and Europe, rather than for egg or meat production. In the last decade there have been a number of genetic studies to clarify the origins. According to one study, a single domestication event occurring in the region of modern Thailand created the modern chicken with minor transitions separating the modern breeds.[24] However, that study was later found to be based on incomplete data, and recent studies point to multiple maternal origins, with the clade found in the Americas, Europe, Middle East, and Africa, originating from the Indian subcontinent, where a large number of unique haplotypes occur.[25][26] It is postulated that the jungle fowl, known as the bamboo fowl in many Southeast Asian languages, is a special pheasant well adapted to take advantage of the large amounts of fruits that are produced during the end of the 50-year bamboo seeding cycle to boost its own reproduction.[27] In domesticating the chicken, humans took advantage of this prolific reproduction of the jungle fowl when exposed to large amounts of food.[28]

It has been claimed (based on paleoclimatic assumptions) that chickens were domesticated in Southern China in 6000 BC.[29]However, according to a recent study,[30] it is unclear whether those birds were the ancestors of chickens today. Instead, the origin could be the Harappan culture of the Indus Valley. Eventually, the chicken moved to the Tarim basin of central Asia. The chicken reached Europe (Romania, Turkey, Greece, Ukraine) about 3000 BC.[31] Introduction into Western Europe came far later, about the 1st millennium BC. Phoenicians spread chickens along the Mediterranean coasts, to Iberia. Breeding increased under the Roman Empire, and was reduced in the Middle Ages.[31] Middle East traces of chicken go back to a little earlier than 2000 BC, in Syria; chicken went southward only in the 1st millennium BC. The chicken reached Egypt for purposes of cock fighting about 1400 BC, and became widely bred only in Ptolemaic Egypt (about 300 BC).[31] Little is known about the chicken’s introduction into Africa. Three possible routes of introduction in about 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.[31] Domestic chicken in the Americas before Western conquest is still an ongoing discussion, but blue-egged chickens, found only in the Americas and Asia, suggest an Asian origin for early American chickens.[31]

A lack of data from Thailand, Russia, the Indian subcontinent, Southeast Asia and Sub-Saharan Africa makes it difficult to lay out a clear map of the spread of chickens in these areas; better description and genetic analysis of local breeds threatened by extinction may also help with research into this area.[31]


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s