It is generally accepted that birds evolved from dinosaurs millions of years ago. However, the exact first bird has not been conclusively determined yet. Prehistoric birds are an interesting and diverse group that evolved from small dinosaurs and gave rise to modern birds.
While the origin of birds, related or not to modern day birds, is disputed, the earliest discovered creature that resembled a bird and had feathers was Aurornis, found to be living 160 million years ago in the Mid-Jurassic Period. Aurornis is not considered to be a true bird because it is as similar to a bird as it is to a dinosaur. As shown in a fossil, it only had downy feathers that couldn’t have possibly let it sustain flight (Strauss).
Ten million years later, Archaeopteryx lived. It is now known to not be the first official bird. Instead, it is a basal bird, a bird which is grouped with the animals that have characteristics of both dinosaurs and birds, like Aurornis and Archaeopteryx. Archaeopteryx had asymmetric, highly developed feathers such as modern birds. This is why Archaeopteryx is believed to be airborne, but it hasn’t yet been determined if Archaeopteryx flapped to fly or glided (Castro, “Archaeopteryx: The Transitional Fossil”).
There is plenty of controversy surrounding the origin of birds. Most scientists support the idea that birds evolved from small dinosaurs, but not all scientists support this. Alan Feduccia, professor of biology at the University of North Carolina, believes that “a huge evolution of birds had been going on before Archaeopteryx, and that they evolved from four-legged forest reptiles” (Davies). Feduccia believes that mammals and dinosaurs evolved similar traits but were of two completely different evolutionary paths, called convergent evolution. He believes that birds were very widespread 135 million years ago, during the existence of Liaoningornis, found alongside Archaeopteryx but living five million years later. He thinks that most of these widespread birds died out with the dinosaurs, the remaining birds giving rise to modern day birds. However, skeptics of the birds from dinosaurs theory are a minority (Davies).
The origin of flight is divided into two groups: the ground-up approach and the top-down approach. The ground-up approach consists of early birds running and flapping on the ground to achieve flight. The top-down approach consists of early birds going to a high location and jumping into flight. A study on how adult and juvenile birds use their wings while running over ramps suggests that wings evolved to help birds get over obstacles, supporting the ground-up approach (Morelle).
Prehistoric birds became more complex as time went on and new species evolved. There were many prehistoric birds, many of which survive today. The first kind of birds to separate from each other were the Neognathae and Palaeognathae. The Palaeognathae are ostriches and tinamous. The Neognathae are all the other bird species. This separation happened approximately 102 million years ago (“Scientists Sequence Genomes of 48 Bird Species, Unveil Avian Family Tree”). After that separation, bird phylogeny has become much more complex. There are now thousands of different species of birds, all ranging from ostriches to penguins to hummingbirds.
A completely different kind of flying creatures called the pterosaurs are often mistaken for birds or dinosaurs. Pterosaurs are not birds or dinosaurs. Pterosaurs were a different kind of reptiles from dinosaurs, and definitely not birds. Furthermore, birds did not even evolve from pterosaurs. Instead, they evolved from small theropod dinosaurs (Castro, “Pterodactyl, Pteranodon, and Other Flying ‘Dinosaurs’”).
Around 65 million years ago, the KT extinction happened. The KT extinction was the extinction that ended the Cretaceous period and the domination of the dinosaurs. Because the first bird evolved with the dinosaurs, birds must have had to survive the KT extinction that ended the Mesozoic. At the time of the KT extinction, the ancestor of modern birds were small feathered maniraptors, which obviously survived the KT extinction.They survived because they were small and could easily adapt to new conditions. Researchers have concluded that the maniraptors’ small size and small food requirement allowed it to find food more easily than the large dinosaurs who didn’t survive because of their enormous size. Because of the dinosaurs’ enormous size, they had more cells to maintain, which means more food was required to stay alive. However, food was not easy to find and they starved while the maniraptors survived, had offspring, and eventually gave rise to modern birds (Balter). If the maniraptors were larger, they would have gone extinct and the widely varying niches that the thousands of species of modern birds now fill today would have been empty and left spaces for other animals to fill, thus affecting the evolution of some other life on Earth. For example, if penguins had not evolved because maniraptors had not survived, then the seals that would’ve evolved alongside penguins would have more fish to eat, perhaps resulting in a greater population of seals than there would have been if the maniraptors had survived and allowed penguins to exist.
Current evidence and the fossil record and what science does know seems to support the theory that birds evolved from small feathered dinosaurs sometime near the late Jurassic. Although the exact debut of the first official bird is unknown, and there is a considerable amount of controversy surrounding the topic, it may not remain that way. With the discovery of new fossils and new evidence that may support or refute our current hypotheses and theories, all that we now believe about the origins of modern could change overnight.
Works Cited
Balter, Michael. "How Birds Survived the Dinosaur Apocalypse." Science Mag News. AAAS, 6 May 2014. Web. 27 Oct. 2015. <http://news.sciencemag.org/evolution/2014/05/how-birds-survived-dinosaur-apocalypse>
Castro, Joseph. "Archaeopteryx: The Transitional Fossil." LiveScience. TechMedia Network, 28 Apr. 2015. Web. 27 Oct. 2015. <http://www.livescience.com/24745-archaeopteryx.html>
Castro, Joseph. "Pterodactyl, Pteranodon & Other Flying 'Dinosaurs'" LiveScience. TechMedia Network, 26 Jan. 2015. Web. 27 Oct. 2015. <http://www.livescience.com/24071-pterodactyl-pteranodon-flying-dinosaurs.html>
Davies, Gareth Huw. "Evolution." PBS. PBS. Web. 28 Oct. 2015. <http://www.pbs.org/lifeofbirds/evolution/index.html>
Morelle, Rebecca. "Secrets of Bird Flight Revealed." BBC News. BBC, 24 Jan. 2008. Web. 27 Oct. 2015. <http://news.bbc.co.uk/2/hi/science/nature/7205086.stm>
"Scientists Sequence Genomes of 48 Bird Species, Unveil Avian Family Tree." SciNews.com. 12 Dec. 2014. Web. 27 Oct. 2015. <http://www.sci-news.com/genetics/science-genomes-48-bird-species-avian-family-tree-02340.html>
Strauss, Bob. "Aurornis." About.com Education. About.com. Web. 27 Oct. 2015. <http://dinosaurs.about.com/od/prehistoricbirds/p/Aurornis.htm>
