A Touch of Evolution: Feathers!

Feathers, like hair, are composed of Keratin; a fibrous protein which bundles itself together to form tough insoluble, unmineralized tissues found in reptiles, birds, amphibians, and mammals. Having evolved from the modern birds' feathered reptilian ancestors, The Feathered Dinosaurs. They are thought to have used feathers primarily for insulation; the feathers grew longer and became useful for running and gliding which lead to the evolution of Proto-Birds: non avian dinosaurs that share a substantial amount of characteristics with birds. Archaeopteryx and Microraptor zhaoianus are examples of proto-birds. The two basic classifications of feathers are vaned; the outer feathers, and down; the insulative feathers beneath the set of vaned feathers.