How did dinosaurs die out?

Dinosaurs died out in the Cretaceous-Tertiary extinction event 65 million years ago. The usual explanation is that a huge meteorite hit the earth and led to extinction (first proposed by four scientists including Dr. Walter Alvarez of the University of California, Berkeley). But this theory is still controversial.

Generally speaking, a meteorite means that after a meteorite hit the earth, a large number of sandstorms flooded the earth and the atmosphere, resulting in the inability of sunlight to directly illuminate the earth's surface, and the temperature in various places gradually became cold. Dinosaurs died and became fossils, because they could not survive and feed in cold climate. There is also a saying that at that time, due to the rapid change of temperature at the two poles of the earth and the rise of sea level, there was a river barrier between the mainland and the mainland, making it difficult for dinosaurs to feed and die.

Asteroid (meteorite) impact theory

This is the most acceptable statement for everyone at present. An asteroid hit the earth, causing extinction, and nearly 90% of life on the earth disappeared. The impact not only caused powerful explosion damage, but also caused a lot of dust to cover the whole earth's atmosphere. The temperature gradually dropped, and sunlight could not penetrate into the earth, so that most plants disappeared because they could not carry out photosynthesis, while herbivorous dinosaurs died because of lack of food, carnivorous dinosaurs gradually disappeared because they did not eat herbivorous dinosaurs, and finally dinosaurs died out. The remaining 10% are small animals and a few plants.

Comet impact theory

This theory is based on the fact that the extinction of paleontology occurs almost every 26 million years. Astronomy believes that there are Oort clouds around the solar system, and the comets in the Oort clouds periodically push toward the sun in the center of the solar system (such as Halley's Comet and Hale's Popper Comet). The extinction of dinosaurs may have been caused by one of the comets hitting the earth.

Theory of orogeny

At the end of Cretaceous, intense orogeny caused the earth's crust to uplift, many shallow seas and lakes turned into land, and some dinosaurs and creatures with water as their home gradually disappeared. The wet swamp also swelled and dried up, so many plants living in the swamp disappeared, so did the herbivorous dinosaurs that ate swamp plants and the carnivorous dinosaurs.

Climate change theory

According to Wei Gena's plate drift theory, the plate distribution in Cretaceous period has changed from Pangu, which was originally connected together, to five continents.

Plate drift itself will cause climate change. For example, Antarctica is located in the middle latitude and has a warm climate. However, due to the plate drift, Antarctica entered the polar circle, which caused the severe cold in Antarctica today.

Because of plate drift, ocean current change and climate change, many places have become cold, hot and dry, which is not suitable for dinosaurs and other creatures to survive. Dinosaurs gradually became extinct.

Volcanic eruption theory

Volcanoes erupt in large quantities and violently, spewing out many greenhouse gases such as carbon dioxide and methane, which has caused the greenhouse effect of the earth. With the increase of temperature, many plants can not adapt to the temperature and die. Herbivorous dinosaurs died because of lack of food, and carnivorous dinosaurs died out one after another.

Ocean ebb tide theory

When something similar to the ice age happens on the earth, the sea water decreases, and there is no barrier between the land and the land, forming a land bridge, organisms will take this opportunity to migrate and promote the exchange and contact between organisms. According to Darwin's theory of "survival of the fittest, elimination of the unfit", the strong will bully the weak and eventually the weak will become extinct.

In addition, there are problems of bacteria, viruses and parasites.

Theory of warm-blooded animals

Some people think that dinosaurs are different from existing reptiles, not cold-blooded animals but warm-blooded animals. But even if dinosaurs were warm-blooded, their body temperature was still not high, probably similar to that of living sloths. In order to maintain such a body temperature, they can only grow in a tropical climate. In addition, the dinosaur's respiratory system is not good, and it can't fully supplement oxygen; The body has no thick hair, and heat is easily lost from the tail, feet and other places; Coupled with the huge body, when the temperature drops suddenly, there is no way to hide in the cave to keep out the cold. So dinosaurs may not be able to withstand the sudden climate change in the late Cretaceous and slowly freeze to death.

Fratricidal theory

Some people think that the real extinction of dinosaurs was the result of killing each other.

When there are more and more carnivorous dinosaurs, more and more herbivorous dinosaurs are preyed. When herbivorous dinosaurs became less and less, or even disappeared, carnivorous dinosaurs began to kill each other. Dinosaurs are extinct.

Oppression theory

The rapid increase in the number of dinosaurs led to the extinction of herbivorous dinosaurs with limited plants, and then carnivorous dinosaurs that ate herbivorous dinosaurs died because of lack of food. Why dinosaurs suddenly increased after about 200 million years of ecological balance is an important key to the establishment of this theory, which directly caused many scholars to review the reasons for the abnormal increase in dinosaur production.

The mammalian prisoner said

In the second half of Mesozoic, the ancestors of mammals existed. According to fossil records, mammals at that time were very small and the number was very limited. It was not until the late Cretaceous that the number began to increase rapidly. It is speculated that they are omnivores whose main food is insects. These small mammals have been eating dinosaur eggs since they found them. Is that really the case? If mammals beat dinosaurs, then with the increase of mammalian fossils, dinosaur fossils should gradually decrease, but in fact there is no such phenomenon of fossil alternation. The real increase in mammalian fossils was after the end of the dinosaur era. Moreover, dinosaur fossils suddenly disappeared. Therefore, the theory that dinosaurs were extinct by mammals cannot be established.

Theory of species aging

People think that the dinosaur's body was too big because it flourished for hundreds of millions of years. Moreover, bones such as horns are also extremely developed, which causes great inconvenience to life and eventually leads to extinction. The most representative dinosaur brontosaurus is 25 meters long and weighs 30 tons. Because of his huge size, he lost his ability to survive. In addition, Triceratops and others also went to the road of self-destruction because of their expanding three horns and unusually developed bones to protect their heads. However, not all dinosaurs are so huge, and there are small dinosaurs with a body length of only about one meter. In addition, there are bones like deer, dinosaurs that can run briskly, but these dinosaurs have also become extinct. Moreover, in cold-blooded animals, abnormally developed bones and other parts are considered to be able to absorb external temperature and release internal heat to regulate body temperature, which has very favorable functions. It can be seen that dinosaurs lived for a long time, so many people suspected that the extinction of dinosaurs was due to the aging of species from a long time ago.

Alkaloid theory

According to this theory, flowering plants began to appear in the last period of dinosaur existence, that is, the Cretaceous period, and some of them contained toxic alkaloids. Dinosaurs died of poisoning because of eating a lot of food. Because mammals can distinguish poisonous plants through taste and smell, but dinosaurs don't have this ability. However, plants containing alkaloids did not suddenly appear in the late Cretaceous, but were already visible five million years before the extinction of dinosaurs.