After analyzing the concentration of oxygen in the last three hundred million years, scientists have come to the conclusion that the oxygen with the appearance of birds is not limited in the size of flying insects.
The scientists analyzed the paleontological data for the last three hundred million years old, which have been divided into sections for ten million years. Scientists have determined the maximum size of the wings, which reached the flying insects in a given period, and correlated them with the oxygen concentration is analyzed.
It turned out that about 300 million years ago, modifications to the maximum dimensions of the wings reflected the fluctuations in the concentration of oxygen. About 130 million years graphs behave differently, despite the fact that the increased concentration of oxygen, the maximum size of the wings did not cease to decrease.
The emergence of the first Archaeopteryx refers to this period (the dinosaurs capable of flight). Researchers believe this is a coincidence is not accidental. Despite the fact that the archeopteryx, perfect flyers, for example such as modern birds do not have, they have influenced the evolution of giant insects.
The greater the size of the animal, the higher the inertness of its flight, making it easier to catch. Over time, the birds and their ancestors with the improvement of flight could catch smaller species, because of what the maximum size of insects gradually decreased.
Currently common hypothesis suggests that the maximum size of insects defined oxygen concentration in the atmosphere. They do not have the blood capillaries and lungs, and gas exchange is carried out in air ducts - the trachea that penetrate the body of animals. The possibility of such gas exchange with the size decrease rapidly that between the oxygen concentration and maximum size of a relationship.
The new study does not contradict this hypothesis, and even more so refines it. Researchers believe that in the late Triassic period, when the oxygen concentration was equal to the current concentration, but the birds did not exist, the size of the wings of insects could reach 18 centimeters, which is twice more than now.