When Dr. Grant argued that birds evolved from dinosaurs in Jurassic Park, his claim was met by laughter from the general public. Grant appealed to the anatomical similarities between dinosaurs and birds to justify this claim. Today, this claim is not met with laughter, but celebrated by paleontologists and evolutionary biologists alike. Yet the exact details about how dinosaurs evolved into birds remain uncertain. In particular, how did feathers evolve and what might the intermediate stages look like?
The fact that birds have nearly globalized the world makes them simultaneously remarkable and second nature. Yet the feathers that coat these magnificent creatures are fascinating. Lighter than a pen and strong enough to glide a weighted creature, the physiology of feathers far exceeds the complexity of a Boeing 747 wing. There is a sharp divide between the edges of a feather. The front edge is stiff and thin, whereas the back-end is long and malleable. These two edges work together to regulate oncoming air and keep the bird aloft.
On the surface, the evolution of feathers might seem an impossible flight. Indeed, Charles Darwin himself wrote the evolution of feathers to be, “the grand case for me.” Yet just two years after the Origin was published, a team of diggers in Germany unearthed a fossilized bird like reptile more widely acclaimed as Archaeopteryx. Archaeopteryx was about the size of a crow, had razor edge teeth, claws attached to the end of its wings and an elongated, ossified tale. Archaeopteryx was the Holy Grail intermediate for paleontologists; however, it was just one of many fossilized treasures soon to be found.
Shortly after, paleontologists unearthed a plethora of fossilized creatures that were reptilian in nature yet contained the faint relics of the most primitive feathers. In doing so, paleontologists began to piece together a picture of feather evolution. The relics of dinosaurs are not lost to a historical extinction but found in their direct descendants: modern-day birds. Before the advent of molecular genetics, this was best seen by the anatomical similarities between dinosaurs and birds. For example, dinosaurs and birds are the only creatures that have a wish bone. Nevertheless, a vexing question still remains: How did feathers evolve in the first place?
To answer this question, scientists look for clues by examining the physiology of modern-day birds. In particular, both scales and feathers are flat. During the course of evolution, it is possible the scales of dinosaurs gradually stretched out and “fissioned” into the complex array of feathered wings. This feet isn’t too much of a leap for the imagination. For example, it would be evolutionary advantageous for lizards that live in canopies to develop elongated scales in order to help them glide from one tree to the next.
Another interesting feature in modern birds is that feathers take on functions other than flight. For example, a woodcock uses it feathers as camouflage, whereas an ostrich uses its feathers to help shades its nest. And who can forget the feathers on the peacock’s tail, which aren’t used for flight at all, but to attract female peacocks. The multiple functions feathers take suggests feathers may have not been originally adapted for flight, as dinosaurs tended to be heavy and short-armed. Rather, feathers could have been used as thermal regulation or to appear larger to prey. The possibilities are endless. Thus, although the evolution of feathers is being sketched, mysteries still remain.
By Nathan Cranford