For centuries, man has been puzzled by the ability of flight in birds and the mystery of its evolution. The classic theory of flight suggests that feathers evolved from reptile scales. Paleontological evidence, however, refutes this theory. Scales and feathers are poles apart in the anatomical context. Unlike feathers, scales do not extend under the skin of the animal and forms only a hard layer on its body.
People have always assumed that feathers were solely evolved for the purpose of flight. Contrary to this belief, today we can find flightless birds that are also endowed with facility of feathers. Fossils hold testimony to establish the fact that even dinosaurs were covered with feathers at some time during the process of their evolution. Proof of this kind also validates an intricate evolutionary link between the dinosaurs and the birds. Dinosaurs had developed feathers to combat the extremity of cold climates.
Back in the Cretaceous era, the feathered theropods, like raptors, could run at very high speeds. This was either for hunting down their prey or trying to outrun their predators. The thin coating of feathers of these theropods gave them an extra lift, an aerodynamic force that let them leap and eventually fly. Gradually, the dinosaur bird transition took place. The small feathers evolved into large ones that were sleek, contoured and strong. Thus, flight evolved from ground up rather than from sky down.
Research does shed light on the evolutionary history of feathers in birds as the result of environmental selection. The feathered dinosaurs that have learned to fly further adapted to the technique of flying. Hollow bones, higher metabolic rates and beaks are some of the changes that birds have adapted to.
The primitive function of feathers, to insulate dinosaurs, has diverged with changing times. Today it serves a different purpose that is fascinating and distinctive in its only surviving descendants - the birds.