The chicken (Gallus gallus domesticus) is a domesticated fowl. As one of the most common and widespread domestic animals, and 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. Conventional wisdom has held that the chicken was domesticated in India, but recent evidence suggests that domestication of the chicken was already under way in Vietnam over 10,000 years ago. From India the domesticated fowl made its way to the Persianized kingdom of Lydia in western Asia Minor, domestic fowl were imported to Greece by the fifth century BC. Fowl had been known in Egypt since the 18th Dynasty, with the “bird that lays every day” having come to Egypt from the land between Syria and Shinar, Babylonia, according to the annals of Tutmose III.