Chickens are 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. 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, 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 5th century BC. 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. The chicken genome has changed less from feathered ancestors eradicated by the Cretaceous–Paleogene extinction event than those of other sequenced avian dinosaurs.