Bird flight, how did it really start ?
On the Evolution of Flight in Archaeopteryx as well as in Pterosaurs
So far, there was no reasonable hypothesis to explain the origin of flight in vertebrates. Several amateurish models have been debated by palaeontologists for more than hundred years. In 1984, a conference took place in Eichstaett, Bavaria, which dealt exclusively with Archaeopteryx, the oldest known animal with feathered wings, and with the evolution of flight ability. The various presentations by the participants were published (M. Hecht et al. 1985). These papers were my first contact to the idea of flight evolution, and I read them enthusiastically. The origin of flight appeared rather mysterious to me, and my hope was to find a convincing explanation. However, the views concerning the evolution of flight adopted in these articles were incredibly naive and not at all based on the principles of flight physics. It is not as easy as palaeontologists with a missing special qualification think it is. On the contrary, some expert knowledge is required to unveil the actual path of evolution. After all, I got an insight into the poor knowledge of the involved workers and into the available fossil material, from which clumsy conclusions had been derived. Unfortunately, in the mean time there has been no progress concerning the abilities of these “experts”.
The main weakness of the old models consists in the fact that they emanate from the forbidden presumption that a primordial wing in the ancestors of Archaeopteryx was already present. However, the problem is just how a wing could develop from an unspecialized arm or forefoot. It cannot suddenly have been present.
Can a moderately critical reader believe that the bird ancestors with a kind of primitive wings had only to learn to use them for flying in the air? According to the opinion of some palaeontologists this should have been an easy task.
In 1995, I found the explanation of the real path which finally resulted in the ability to fly high in the air. Although the solution was not simply obvious, nevertheless in most cases the hard parts of fossils yield sufficient informations for a reliable reconstruction of the former lifestyle. In this case it was the long bony tail of Archaeopteryx, and additionally the same feature in long-tailed pterosaurs, in both forms stiffened, which offered the decisive hints. This feature is very obstructive for flying high in the air, nevertheless it must have served a special purpose. In addition, in both forms the finger claws are still present. In later birds such as Eoalulavis from the lower Cretaceous of Spain and in all Recent birds they are replaced by the important alula. Thus, these early forms can hardly have been flyers high in the air.
The well preserved Berlin specimen of Archaeopteryx. Particularly conspicuous are the long bony tail and the sharp claws of the hands as well as teeth.
The first find of the Urvogel opened a path to the evolution of birds, since this animal presented old reptile features on the one hand, on the other bird features pointing to a close relationship between reptiles and birds. In particular, the long bony tail and the sharp claws of the manus are conspicuous. These traits cannot be found in modern birds, and they are indicative of aggravating differences. Therefore, many workers have correctly considered that Archaeopteryx cannot yet have been a true bird. However, the mystery persisted how the wing could have evolved, and this fact was used for attacks against Darwin’s idea of evolution, because the wing was seemingly suddenly present. Darwin correctly supposed that the wing would previously have had a different function, though he did not know which one.
Archaeopteryx did not lead to unequivocal statements about the evolution of active flight, as little as did the previously known pterosaurs. However, certainly there is a path leading from reptiles to flying vertebrates. The glider hypothesis as well as the runner hypothesis could not at all convince me because of their imminent weaknesses. Maybe, I am better qualified to develop a new theory than anybody else, since I have expert knowledge in this field. I was interested in flight from my earliest years, have designed model airplanes, was an active glider pilot for many years, have studied flight physics, and have worked in the department of aerodynamics and flight mechanics at Dornier Aircraft Company since 1965. On the other hand, I have discovered my passion for fossils and their lifestyle several decades ago, obviously a favourable coincidence.
When I began to deal with the evolution of flight I was very disappointed by the amateurish ideas presented so far. Admittedly, I did not immediately have an answer either, but I noticed that the presented ideas could not be correct. Up to now, biologists, palaeontologists, and further -gists have used very poor lines of argumentation, needless to say they are completely wrong. Experts in anatomy or in ornithology are by no means qualified by this knowledge to reconstruct successfully the origin of flight. Using their simple arguments they do Darwin an injustice and demonstrate that they do not have understood the principles of evolution. Darwin has well formulated his ideas and has well recognized the real problem. In any case, in birds, pterosaurs, as well as in bats, there must be an uninterrupted path from unspecialized arms and hands to a flying wing by means of mutation and natural selection. To narrate such simple stories as those heard in Eichstaett and still today by so-called experts would have been an easy task to Darwin, yet he resisted the temptation. He was a true scientist
The long-tailed pterosaur Rhamphorhynchus. Laymen only can identify such an animal as a flyer in the air. It is well known that penguins also have wings, but do not fly in the air.
This well-known pterosaur from the Upper Jurassic shows the same characteristic features of an underwater flyer as Archaeopteryx, namely a stiffened long bony tail as well as the retained finger claws. The long heay tail results in an unfavourable position of the center of gravity, and it had to become rudimentary to effect a resulting forward shift in flyers in the air.
fHow could bird flight really develop?
The real problem onsists in the question how a wing could develop that is capable of generating lift and propulsion. This is an old mystery for unfortunately incompetent experts, but it is simply ignored, the presence of a well developed wing is taken for granted. Although there had been considerations about its evolution since Archaeopteryx had been found 150 years ago, but a convincing solution could not be found. Since the evolution was successful several times it cannot have been extremely difficult.
Flight developed in forms which were fish hunters, swimming under water. Physics does not allow alternative solutions.
TFlying under water is not unusual in modern birds. All sea birds are fish eaters, and many of them use their wings for generating propulsion under water, for instance aulks and penguins. Actually, the starting point for the evolution of wings in vertebrates was the pursuit of fish. During the Upper Triassic some small reptiles modified their former method of hunting, which presumably consisted in hunting fish while wading in shallow water, and now used the forelimbs for propulsion. The evolution lead to representatives related to Rhamphorhynchus.The occurring developmental changes helped to extend the radius of effective range considerably. As a matter of fact the wings developed originally for the generation of propulsion. Later on they were suited for flight in the air, too. Wings are capable to move water as well as air.
Recenly found well preserved eggs prove the close dependency on the water
Recently discovered soft-shelled eggs of pterosaurs can serve as an excellent confirmation for the origin of pterosaurs from the water (Ebel 1996). Very different suppositions lead to a convergent solution in Archaeopteryx and in pterosaurs. Archaeopteryx was predominantly a land-dweller. She adapted to the pursuit of fish under water. She was equipped with a warming plumage and, therefore, may have been able incubate her eggs.
Contrasting to Archaeopteryx the ancestors of the pterosaurs were predominantly water-dwellers. The missing plumage did not allow them to breed. As all egg-laying vertebrates living in or in its immediate vicinity the water, for example turtles or crocodiles, they had to bury their soft-shelled eggs on land in soft ground and have them incubate by the ground warmth. For this purpose the fingerclaws could be utilized, maybe this was their primary function. After hatching the poorly developed hatchlings had to run as fast as possible to reach the saving water. It was the most dangerous moment of their life, as can be observed in freshly hatched turtles.
.The long-tailed pterosaurs such as Rhamphorhynchus remained in the water as underwater fish hunters for their whole life. However, the short-tailed pterosaurs such as Pterodactylus, which appeared in the Upper Jurassic, had also to spend a relatively long time in the water, namely until their individual development enabled them to fly in the air. They too remained connected to the water, because for later egg deposition they had to return.
Archaeopteryx and long-tailed pterosaurs resemble in a way modern penguins as to their lifestyle.
The recently found soft-shelled eggs validate this context, furthermore they offer a good opportunity to palaeontological pterosaur experts to demonstrate the complete incompetence in interpreting their finds. Obviously, palaeontologists are unable to recognize that pterosaurs originate from the water. They never noticed the fundamental difference between long-tailed and short-tailed pterosaurs. Apparently, even the process of evolution is unknown to them. Unfortunately, the mere knowledge of bones is too little to become an expert.