What is the Theory of Dinosaur to Bird Evolution
The Theory Forms
Not many people know that the theory that birds evolved from dinosaurs is almost as old as dinosaur paleontology itself. It dates back to same period Darwin was starting to propose his theory of evolution. Darwin was not immediately liked. In fact one of his proponents was a Thomas Henry Huxley, a 20-something year old self-taught biologist and anatomist. Normally such a person wouldn't take up much time or attention from the intellectual elite at the time but there was something about this young man that drew Darwin to him. He wished to convince him that the theory of evolution was not just hot air and that's what he did. Within a few years Huxley went from an ardent disbeliever to a proponent of Darwin's theory. In Darwin's later life Huxley took on the challenge to show the world the advancements of science and evolutionary theory. He was the first to call himself Darwin's Bulldog.
During this time he also was busy in his own studies and was becoming an expert in reptilian fossils. A strange fossil had been found in 1861 that was named archaeopteryx. It was 145 million years old and appeared to be a very primitive bird with flight feathers and wings. However it was strange in the fact it's skeleton, and particularly its head, all looked more like a lizard then a bird. It had rows of sharp teeth where a beak should have been and maintained three claws on its wings and back feet that resembled dinosaurs more then birds. Huxley took this to mean that small carnivorous dinosaurs had evolved through time to become birds. He had his supporters and believers at the time but the theory had long fallen out of favor by the time I came around. Still, it was intriguing. Modern paleontologists often avoided the subject, unable to explain why it had combined features, they eventually classified it as a bird. There was no other fossils found with more primitive feathers or other links on this evolutionary chain. Paleontologists considered it an evolutionary dead end, not the ancestors of birds. Few kept this accused antiquated belief in dinosaur birds.
Feathered Dinosaurs Motherload Found in China
Starting in 1994 a series of discoveries were made in China by farmers. They unearthed a treasure trove of feathered dinosaur and primitive bird fossils that dated between 120-145 million years ago. They were the first to find not only one missing link but dozens, showing a clear picture and proving therapods were indeed bird ancestors.
The first of the feathered dinosaurs perplexed modern paleontologists. It was titled Sinosauropteryx prima and it looked entirely like a therapod dinosaur with one exception, it was covered in hair-like down feathers. Paleontologists clamored together and theorized that feathers evolved to keep these dinosaurs warm or protected from the elements. Some claimed feathers likely evolved many times and this was not the infamous avian ancestor.
Then Sinornithosaurus was discovered. It was another dinosaur covered in down feathers but this time it had a little more. It had stiff feathers on its arms, not unlike flight feathers, but not enough to actually aid in flight or gliding. These could have evolved for ornamentation to attract a mate or to keep balance while they were chasing prey. These dinosaurs had long arms used for snatching prey and drawing them nearer to their dreadful teeth.
Just as the paleontologists were starting to get worried their disbelief was wrong more fossils were found. This time they were like archaeopteryx with full flight feathers and covered bodies but some of these had lost the lizard-like tail and were evolving beaks. It was theorized these earliest of birds were gliders who lived in the trees and caught prey far above the ground. However when biologists started to study bird flight from various angles they noticed something strange. Flighted birds did not flap their wings up and down as most would have hypothesized. Instead they made a strange figure eight-like movement with their wings, almost as if they were swimming through the air. This is what gave them maximum lift. It wasn't long before paleontologists realized this would have been the same movement a theropod would make if it were grasping prey with its fierce claws and long arms. Flight it seems was something of a happy accident.
So now the dinosaur to bird theory is again in popular favor where it always belonged. Instead of being an outdated idea it's an idea that's being expanded as new questions arise. For example, how and why did down feathers evolve into stiff feathers? The jury is still out as paleontologists bicker quietly amongst themselves. Someday the public may know where the truth lies.
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