用英文介绍鸡

The chicken is a domesticated fowl. Recent evidence suggests that domestication of the chicken was under way in Vietnam over 10,000 years ago.Until this discovery, conventional wisdom held that the chicken was domesticated in India.
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.

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