The domestic chicken

Origins

The domestic chicken is descended primarily from the Red Junglefowl (Gallus gallus) and is scientifically classified as the same species.[17] As such it can and does freely interbreed with populations of red jungle fowl.[17] 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).[18]

Researchers have found chickens' bones in unusual amounts and out of natural jungle range, thus denoting a breeding place. Bones of domestic chickens from about 6000-4000 BC have been found in Yangshao and Peiligan, China, from a time when the Holocene climate was not naturally suitable for the Gallus species.[19] Archaeological data is lacking for Thailand and southeast Asia.

Later traces are found about 3000-2000 BC in Harappa and Mohenjo-Daro, Pakistan,[20] and -according to linguistic researchers- in Austronesian populations traveling across southeast Asia and Oceania. A northern road spread chicken to the Tarim basin of central Asia, modern day Iran. The chicken reached Europe (Romania, Turkey, Greece, Ukraine) about 3000BC, and the Indus Valley about 2500 BC.[21] 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.[21] 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 1400BC, and became widely bred only in Ptolemaic Egypt (about 300 BC).[21] Little is known about the chicken's introduction into Africa. Three possible ways 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.[21] Domestic chicken in the Americas before Western conquest is still an ongoing discussion, but blue-egged chicken, found only in the Americas and Asia, suggest an Asian origin for early American chickens.[21]

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.[21]





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