The chicken is an extant species of avian dinosaur. They are a domesticated subspecies of the Red Junglefowl, and are estimated to have diverged from this main species around 8000 years ago. Though not their initial purpose, chickens are kept primarily as a source of food. They are large producers of meat and eggs.
Along with all other birds, chickens are considered avian dinosaurs. Avian dinosaurs are the only members of clade "Dinosauria" that survived the K-T extinction event which had wiped out three quarters of all life on Earth.