In the distant past, giant animals inhabited the Earth. Among them were powerful dinosaurs, pterosaurs the size of an airplane, giant crocodiles and snakes, and armadillos the size of a car.. But today there are only a few large species left on our planet.. Why did this happen? The answer to this question is published by the publication Live science.

There is plenty of fossil evidence that giant animals lived on Earth in the past.. Not only were they gigantic, but their average size was larger than that of modern fauna, said University of Florida paleobiologist Greg Erickson.. Ever since scientists unearthed the first batch of dinosaur bones in the 19th century, they have been trying to explain why giant animals were common millions of years ago but are rare today.. But, according to Erickson, no one can give an unambiguous answer..

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However, this circumstance may explain several key differences between dinosaurs and today's large animals - mammals.. Like other reptiles, dinosaurs could adapt to different niches as they grew, preying on smaller prey when young and larger prey as adults.. This was partly possible due to the fact that they changed different sets of teeth, as sharks do.. That is, as reptiles got bigger, they exchanged their juvenile set of teeth for larger "

According to University of Edinburgh paleontologist Steve Brusatte, dinosaur air sacs spread from the lungs to the bones, creating strong but lightweight scaffolds.. Thanks to this, dinosaur skeletons were strong and flexible, but still light, which allowed them to grow bigger and bigger.. Mammals do not have air sacs that can penetrate and lighten bone..

As warm-blooded or endothermic animals, mammals need a lot of food, while dinosaurs were cold-blooded animals.. This means that the need for food in an elephant is about five times greater than in the largest dinosaurs..

Paleontologists debate whether dinosaurs were warm-blooded or cold-blooded. Modern science places animals on a gradient between cold-blooded and warm-blooded, and dinosaurs were probably at the " That is, the large body of a dinosaur was less energy-intensive.

For the gigantic size of the body, an appropriate environment was also necessary.. In a study published in 2016, scientists concluded that gigantism is directly dependent on a sufficient amount of resources produced and processed by " That is, there must be enough oxygen, food and space in the environment for a giant creature to grow in it.. Similar environments developed by the middle of the Triassic period, closer to the beginning of the era of dinosaurs..

The ancient atmosphere had a high concentration of oxygen. This may have played an important role in the development of gigantism, especially in insects.. A 2012 study showed that the wingspan of fossil insects showed an increase in oxygen concentration..

In addition, time also played an important role.. In order for a species to develop to a gigantic size, it takes a very long time for evolution.. Mass extinctions, on the other hand, destroy, as a rule, larger creatures, so the niches of such animals can remain unfilled for tens or even hundreds of millions of years..

" For example, woolly mammoths became extinct only 10 thousand years ago.. Therefore, it is not surprising that modern people do not see such gigantic creatures: our own ancestors helped to destroy them not so long ago..

Vermeil believes that the most comprehensive explanation for the decrease in the size of animals comes not from the features of physiology and the environment, but from the social structure.. According to him, " Group hunting of even relatively small predators makes even very large prey vulnerable.

“Individual gigantism on land has actually been replaced by group gigantism,” the scientist believes..

That is, group hunting of animals such as wolves and hyenas is a more effective way to become big than creating a big body.. As a result, "

Social organization may also explain why the largest known animal still exists in the ocean: blue whales.. The marine environment makes it difficult to communicate over long distances, making it more difficult to create large hunting groups..