The evolution of animals is a very fascinating area of science, and in certain cases enigmatic, because let's think about all the events that occurred over millions of years so that, from a planet without life, the conditions were given not only for the development of the first basic life forms, but also for the amazing display of biodiversity that we have today. Within this evolutionary path we find the birds, a distinctive group due to their relationship with the dinosaurs, who have traveled a long path of transformations over millions of years. If you want to know the origin and evolution of birds, continue reading this article on our site.
When did the first birds appear?
The fossil record has made it possible to determine that birds arose in the Jurassic, which corresponds to the second period of the Mesozoic, which occurred about 150 million years ago During the Cretaceous-Paleogene limits, a mass extinction event occurred, including the dinosaurs and much of the lineage of these feathered animals. However, a group managed to survive this event and allowed evolution to give rise to today's birds, as well as the rise of mammals.
Origin of birds from dinosaurs
It is a general consensus in the scientific community that the origin of birds is linked to the dinosaurs, since, for example, in countries like China and Spain fossils were found that give evidence of this close relationship between birds and dinosaurs, one case being the discovery of the remains of a dinosaur with traces of feathers. However, some other specific aspects, such as those related to phylogenetic relationships, have been the subject of debate.
One of the first proposals of this relationship was made from the Archaeopteryx finding, which corresponded with asmall dinosaur very similar to a bird , found in Germany in the early 1860s. The name refers to the combination of Greek words meaning "feathers" or "ancient wings". It is also eventually called Urvogel, which translates to "primitive bird" in German. This genus has been considered a key piece in the transition between dinosaurs and birds, since a series of anatomical characteristics of both groups have been identified in it. Thus, Archeopteryx reached the approximate size of a modern crow, weighed about 1 kg and had feathers with certain similarities to those of modern birds. However, it has been estimated that this animal really didn't fly like the species that do today, but it did manage to move through the air over short distances, something that has also been proposed for some of its relatives, which may have corresponded as a preparation for later real flight in birds. As for the traits it shared with non-avian dinosaurs, we found the presence of claws, teeth (small), a long tail with bone and absence of hollow bones
However, with the passage of time and the discovery of new findings, the definitive explanation of the origin of birds, far from being resolved, has become even more complex, mainly due to the discovery of fossils that they corresponded to other avian dinosaurs, probably more directly related to birds. In this regard, Archeopteryx has continued to play an important role, but it has been proposed that, instead of being a direct ancestor of birds, is a relative of ancestors with which this group of flying animals is directly related. What is clear is that within the feathered theropod dinosaurs are the ancestors that gave rise to birds.
How did Archeopteryx come about?
The phylogenetic position of this genus has been the subject of debate and even controversy, since two different evolutionary lines have been proposed: one that points to being an ancestor of current birds and another that includes it in the group of feathered dinosaurs, but not closely related to birds. In this sense, if this last proposal is true, then it would mean that their ability to fly arose independently of that of the true ancestors of today's birds.
It has been suggested, then, that Archeoptheryx arose from Anchiornithidae, with which it has been determined to share biological aspects and is probably one of the oldest basal groups of birds In turn, this last family comes from Deinonychosauria, closely related to feathered dinosaurs. Finally, all of these have as their basal group the so-called "paraves", where, in addition to many extinct species, current birds are located.
Without a doubt, it will be necessary to continue investigating to find the exact origin of birds, since, although they are related to flying dinosaurs, we already see that they do not descend directly from them.
Evolution of birds over time
Currently, birds are a highly diversified group with around 10,000 species, which vary considerably in size and weights, since we find individuals such as large ostriches and small hummingbirds at opposite ends. On the other hand, they have varieties of habits and roles in ecosystems, thus, some are more terrestrial, others have a great capacity for flight or certain species have good swimming abilities; there are also variations in diet.
Despite the great massive extinction event that occurred in the Cretaceous-Paleogene, all of the above indicates that birds have had a complex evolutionary process through time. This can be evidenced thanks to the extraordinary radiation that the group had. Thus, after the massive extinction process that affected diversity in general and ended with the disappearance of the dinosaurs, only a few lineages of birds managed to survive to continue its evolution. These were the group of ostriches and their relatives, the group of ducks, geese and swans, which are aquatic birds, the galliformes, where land birds are located, and the group known as "neoaves", which encompasses most of the modern species, with a varied diversity of customs.
Now then, how was the evolutionary process of birds? We see it.
How did birds evolve?
Birds, although they descend from the dinosaurs, it has been proposed that they lived with them for a time, since they had evolved before the mass extinction eventsuffered by these peculiar animals. However, their modern characteristics appeared, according to the fossil record, after the general decline of these prehistoric chordates.
In a very general way, it can be stated that the change that occurred towards the bipedal form of movement in groups of ancestral dinosaurs led, along with other transformations, to the evolution of birds. This form of locomotion resulted in the forelimbs no longer being useful for support, but later they became functional for flight, which also happened, according to it is estimated, gradually.
Other changes in this evolutionary process that were giving way to birds as we know them is the reduction of anatomical structures, such is the case of the long bony tail, in which there was a fusion of the last vertebrae, in addition to the replacement of the tail by the feathers in this region of the body. The legs also had an improvement, since they became very versatile, useful and adapted to different functions. In fact, today we see the advantages of these adaptations in the different habitats where birds live.
On the other hand, the rib cage became more rigid, the shoulders became stronger to be able to rise up and maintain continuous flight, in addition, the wings were specialized to also land, both in a coordinated and effective way.
We can point out that the entire radiation process that gave rise to the diversification of modern birds occurred in the Cretaceous, which is why some of them were better prepared to survive the extinction event that followed.
