Dinosaurs are terrestrial vertebrates that lived on Earth during the Mesozoic era. They first appeared between 247 and 240 million years ago. Dinosaurs lived on Earth for about 175 million years.

It is believed that the last dinosaurs went extinct approximately 65 million years ago. This is the end of the Cretaceous period - the last period of the Mesozoic era. There are various theories as to why this happened.

Theories about the extinction of dinosaurs have become the subject of much debate. Scientists have not yet come to a consensus.

Huge asteroid

One of the popular theories, supported by a large number of scientists, is the theory that a huge asteroid (or group of asteroids) crashed into the Earth near the Gulf of Mexico.

The asteroid was so huge that the dust and debris that rose into the air as a result of its impact blocked the Earth from sunlight. Mountains formed at the site of the asteroid impact. The tsunami buried plants and animals under thick piles of rubble. The planet cooled and remained that way for many years. On Earth, climate conditions actually changed, and most species of animals and plants became extinct.

A deadly chain of events occurred. Without the sun, plants died. Without plants, herbivores died. Without herbivores, predators died.

There is one problem with this theory that may undermine its plausibility. Paleontologists have not found dinosaur skeletons in the rocks dating back to the period of the asteroid impact. Some evidence even suggests that all dinosaurs died before the asteroid hit Earth.

Volcanoes

There is another scientific theory that concerns volcanoes. Scientists have found plenty of evidence that even before the asteroid hit, life on Earth was already in trouble.

Multiple volcanic eruptions released molten rock and corrosive gases. They could acidify the oceans. All this could have created an imbalance in the ecosystem long before the asteroid hit.

When dinosaurs lived on Earth, the climate was most likely hot and humid. No evidence of an ice age or glaciation has been found in the rocks of this period. Carbon dioxide was close to current levels.

The ice caps at the North and South Poles have melted, causing sea levels to rise. Australia was breaking away from Antarctica and gradually moving away from the South Pole, closer to the equator.

The landscape was dominated by conifers and ferns, and the first flowering plants appeared. About half of Australia was covered by shallow inland seas.

This data was obtained from archaeological excavations of fossils found in the rocks of this region. They contain marine molluscs and large prehistoric reptiles such as ichthyosaurs and plesiosaurs. Today this area is called the Great Artesian Basin.

But what happened to the climate during this period? Between the Early and Middle Cretaceous periods, Earth's climate warmed by as much as 10°C. Some scientists have linked this phase of global warming to the enormous impact of asteroids. Others attribute it to the large number of volcanic eruptions in the area that is today India and Pakistan.

Many great changes occurred during the Late Cretaceous. Continents were destroyed, volcanoes released ash and gas into the atmosphere, rapidly changing the climate. Wind and ocean currents have changed. Sea levels have dropped. Marine changes, combined with volcanic influence, may have caused the mass extinctions.

Other theories

Some scientists believe that the cause of the extinction of dinosaurs was mass diseases and epidemics (such as plague). As a result, entire populations of dinosaurs disappeared.

There are theories about the influence of space - a burst of gamma radiation damaged the Earth's ozone layer, and this led to irreversible consequences in the climate and the development of creatures.

There is also a theory about the influence of flowering plants. As a result of the spread of flowering plants on Earth, dinosaurs were poisoned by them, since such plants contain alkaloids (these are important active substances of plants).

There are a lot of theories about the extinction of dinosaurs, some seem more plausible, and some even fantastic.

Dinosaurs(Latin Dinosauria, from ancient Greek δεινός - terrible, terrible, dangerous and σαῦρος - lizard, lizard) - a superorder of terrestrial vertebrates that dominated the Earth in the Mesozoic era - for more than 160 million years, starting from the Upper Triassic period (approximately 225 million years ago) until the end of the Cretaceous period (66 million years ago), when most began to go extinct during a large-scale extinction of animals and many plant species in a relatively short geological period of history. Fossil remains of dinosaurs have been found on all continents of the planet. Nowadays, paleontologists have described more than 500 different genera and more than 1000 different species, which are clearly divided into two orders: ornithischians and lizards.

The most famous versions of the extinction of dinosaurs

Nobody knows the exact reason. But there are a great many theories about the death of dinosaurs. Most of them suggest that there were some strong changes in the climate of our planet, which damaged many living organisms, not just dinosaurs. The most popular theory claims that dinosaurs and other animal species became extinct due to one terrible universal catastrophe: 65 million years ago, the Earth collided with an asteroid, and a terrible explosion occurred. Interesting fact: in addition to dinosaurs, flying reptiles and a large number of marine inhabitants became extinct 65 million years ago.

Asteroid hypothesis

Story

By examining clay deposits in layers of the Earth's crust dated to have been deposited 65 million years ago, scientists have found high levels of iridium in these rocks. Iridium is rarely found on Earth, since during the formation of our planet, iridium, as a heavy element, sank deep underground and is found mainly near the earth's core. Iridium only reaches Earth from space when meteorites and asteroids fall from the sky. Scientists have found iridium in ancient clay deposits around the world. Here is their conclusion: the iridium fell from a cloud of dust that was thrown into the atmosphere when the asteroid collided with the Earth. Thus, the fall of an asteroid is one of the most common versions.

It is based mainly on the approximate timing of the formation of the Chicxulub crater (which is the impact of an asteroid of about 10 km in size about 65 million years ago) on the Yucatan Peninsula in Mexico and the time of extinction of most of the extinct dinosaur species. In addition, celestial-mechanical calculations show that asteroids larger than 10 km collide with the Earth on average about once every 100 million years, which in order of magnitude corresponds, on the one hand, to the dating of known craters left by such meteorites, and on the other – time intervals between the peaks of extinctions of biological species in the Phanerozoic.

Lack of theory

Many scientists, however, are skeptical about this theory. Why then, they ask, did birds, crocodiles, turtles, snakes and most mammals survive, as well as insects, shellfish, ocean fish, and many plants? This theory is also questionable because the extinction of dinosaurs occurred very slowly - over millions of years, and not during one gigantic cataclysm.

Advantage of theory

The only advantage of the asteroid theory is that it can be tested. Scientists were looking for a crater of suitable size. Looking at space photographs of Mexico, they discovered a semicircular chain of lakes. These lakes on the Yucatan Peninsula may border the edges of a giant crater buried under one and a half kilometers of rock. In 1992, scientists obtained rock samples from deep within the supposed crater while the Mexican National Oil Company was drilling at the site. After dating the samples, scientists determined that the crater is indeed about 65 million years old. At the same time, scientists examining leaf fossils from rock samples dating back 65 million years found that these leaves had been severely damaged by severe frost. The stage of leaf development showed that they froze in June. The leaf fossils provide further evidence that rock debris and dust thrown into the air by the big explosion may have suddenly cooled the air temperature. Scientists, however, argue that this event, even if it did occur, could have caused the extinction of the dinosaurs.

Supernova explosion or nearby gamma-ray burst

In 1971, physicist Wallace Tucker and paleontologist Dale Russell suggested that a supernova explosion located quite close to the solar system at the end of the Cretaceous period could have catastrophic consequences for life on Earth. As a result of such a supernova explosion, the upper layers of the planet's atmosphere were exposed to X-rays and other types of radiation, which caused rapid climate change, and the temperature on Earth began to drop rapidly, but no evidence of such an event was found.

Volcanic activity

Story

Increased volcanic activity, which is associated with a number of effects that could affect the biosphere: changes in the gas composition of the atmosphere; the greenhouse effect caused by the release of carbon dioxide during eruptions; changes in the Earth's illumination due to emissions of volcanic ash (volcanic winter). This hypothesis is supported by geological evidence of a gigantic outpouring of magma between 68 and 60 million years ago on the territory of Hindustan, as a result of which the Deccan Traps were formed.

Research

New data obtained by a group of international researchers from Princeton and the Massachusetts Institute of Technology (USA), the University of Lausanne (Switzerland) and the University of Amravati (India) suggests that - yes, volcanoes could literally drive dinosaurs to their graves. Michael Eddy and his colleagues were able to more or less accurately determine the age of geological formations in the Deccan Traps, one of the largest igneous formations on the planet, located on the Deccan Plateau in western and central India. (The term trap, which is used in geology to denote this type of relief, comes from the Swedish word trappa - ladder.) From such geological zones it is possible to determine the time and duration of large-scale volcanic "seasons" that occurred in the distant past.

Igneous rocks were dated using zircon, a uranium-bearing mineral that forms in magma shortly after an eruption, so it can be used to fairly accurately determine the age of sediments. The chemical “clocks” here are uranium isotopes. It was possible to find samples of zirconium corresponding to the beginning and end of the volcanic period. As the authors of the work write in Science Express, the eruptions began 250 thousand years before the fall of the alleged asteroid and continued for another 500 thousand years after, throwing out about 1.5 million square kilometers of lava.

Such prolonged volcanic activity could not but affect the chemical composition of the atmosphere and the oceans: substances appeared in the air and water that ruined the lives of many organisms. One of the most abundant volcanic “gifts” could be carbon dioxide, which, once in the ocean, greatly acidified it, thereby killing some of the plankton. Which, of course, affected all food chains that started with marine plankton. Of course, no one says that external intervention in the form of an asteroid had no effect on the Earth’s biosphere. There was an asteroid, and it affected the biosphere, but the ecology was already largely shaken by internal reasons, so the collision could only accelerate what would have happened anyway.

Change in Earth's gravity

One of the most recent versions suggests that giant lizards disappeared due to an increase in the Earth's gravitational force. The theory is based on the fact that planets gradually increase in size. This means that their mass and force of attraction also increase. This circumstance could well have affected the mobility of dinosaurs, as well as other creatures. To understand why this happens, we can recall an example of such a phenomenon as complete weightlessness in outer space on ships. That is, the lower the force of gravity, the easier it is to move. The weight of the dinosaurs was too high, and their bodies might not actually be able to adapt to such changes. Every day it became harder and harder for them to move, which significantly hampered their search for food and their life processes in general.

Continental drift

Dinosaurs, according to scientists, lived in the Mesozoic era (248-65 million years ago). The Mesozoic, in turn, is divided into the Triassic, Jurassic and Cretaceous periods. Initially, all the continents made up a single giant continent called Pangea. During the Jurassic period, Pangea gradually “broke” in half, and land parts began to move away from each other. By the time of the extinction of the dinosaurs, the continents had moved even further apart. The contours of the continents began to resemble modern ones. Continental drift could have caused the extinction of dinosaurs, because their habitats changed dramatically, as did climatic conditions. The vegetation has changed, and it has become more difficult for herbivorous lizards to get food. With their numbers declining, hard times also came for the carnivorous dinosaurs.

Epidemic

Based on Charles Darwin's theory of evolution, bacteria and microbes appeared before all other forms of life on Earth. The processes of evolution did not bypass them, and these microorganisms mutated. Thanks to such statements, a new hypothesis was born about why giant lizards became extinct. Any living organism adapts to changing environmental conditions, but not all inhabitants of the Earth can live with different bacteria on the principles of mutualism (“mutually beneficial cohabitation”). Therefore, the version that the dinosaurs were destroyed by an epidemic has the right to life. It is quite possible that most of the epidemics that at one time destroyed a huge number of people also destroyed the dinosaurs millions of years ago. The proof of this theory can only be knowledge about some properties of microorganisms. The fact is that bacteria survive under a wide variety of environmental conditions. In severe frosts, they do not die, but simply curl up into a cyst. This shell allows microbes to live for a huge number of years in the so-called sleep mode. As soon as conditions again become suitable for the life of microorganisms, they “wake up” and begin to multiply.

Dinosaurs were exterminated by the first predatory mammals

The theory states that mammals turned out to be more advanced in terms of survival, it is easier for them to obtain food and adapt to the environment. The main advantage of mammals was the difference between their method of reproduction and the method of reproduction of dinosaurs. The latter laid eggs, which could not always be protected from the same small animals. In addition, the small dinosaur needed a huge amount of food to grow to the required size, and food became increasingly difficult to obtain. Mammals were carried in the womb, fed with mother's milk, and then did not need too much food. Moreover, there were always dinosaur eggs under our noses, which could be capitalized unnoticed.

From a paleontological point of view

The great extinction version is based on the following facts:

1. The appearance of flowering plants.
2. Gradual climate change caused by continental drift.

According to the scientific world, the following picture was observed. The developed root system of flowering plants and their better adaptability to soils quickly replaced other types of vegetation. Insects that fed on flowering plants began to appear, and insects that had previously appeared began to disappear.

The root system of flowering plants began to grow and prevent the process of soil erosion. The land surface stopped eroding, and nutrient material stopped flowing into the oceans. This has led to the depletion of the ocean and the death of algae, which, in turn, are producers of biomass in the ocean. The ecosystem was disrupted in the water, which caused a mass extinction. It is believed that flying lizards are closely related to the sea, so the chain of extinction spread to them. On land they tried to adapt to the green mass. Small mammals and small predators began to appear. This was a threat to the offspring of dinosaurs, since eggs and baby dinosaurs became food for the emerging predators. As a result, conditions were created that were negative for the emergence of new species.

When the dinosaurs became extinct, the Mesozoic era ended, and with it, active tectonic, climatic and evolutionary activity also ended.

Combined theories

The above hypotheses can complement each other, which is used by some researchers to put forward various kinds of combined hypotheses. For example, the impact of a giant meteorite could provoke increased volcanic activity and the release of a large mass of dust and ash, which together could lead to climate change, and this, in turn, changes the type of vegetation and food chains, etc.; Climate change could also be caused by lowering sea levels. The Deccan volcanoes began to erupt even before the meteorite fell, but at a certain point, frequent and small eruptions (71 thousand cubic meters per year) gave way to rare and large-scale ones (900 million cubic meters per year). Scientists admit that a change in the type of eruptions could have occurred under the influence of a meteorite that fell at the same time (with an error of 50 thousand years).

It is known that in some reptiles the phenomenon of dependence of the sex of the offspring on the temperature of egg laying is observed. In 2004, a group of researchers from the British University of Leeds, led by David Miller, suggested that if a similar phenomenon was typical for dinosaurs, then climate change of just a few degrees could provoke the birth of individuals of only a certain sex (male, for example), and this, in turn, makes further reproduction impossible.

Disadvantages of hypotheses

None of these hypotheses can fully explain the entire complex of phenomena associated with the extinction of dinosaurs and other species at the end of the Cretaceous period.

The main problems of the listed versions are as follows:

• The hypotheses focus specifically on extinction, which, according to some researchers, proceeded at the same pace as in the previous time (but at the same time, new species ceased to form within extinct groups).
• All impact hypotheses (impact hypotheses), including astronomical ones, do not correspond to the expected duration of its period (many groups of animals began to die out long before the end of the Cretaceous). The transition of the same ammonites to heteromorphic forms also indicates some kind of instability. It may very well be that many species had already been undermined by some long-term processes and were on the path to extinction, and the catastrophe simply accelerated the process.
• On the other hand, it should be borne in mind that the duration of the extinction period cannot be accurately estimated due to the Signor-Lipps effect associated with the incompleteness of paleontological data (the time of burial of the last found fossil may not correspond to the time of extinction of the taxon).
• Some hypotheses have insufficient factual evidence. Thus, no traces have been found that reversals of the Earth’s magnetic field affect the biosphere; there is no convincing evidence that regression of sea levels could cause a mass extinction of such proportions; there is no evidence of sharp changes in ocean temperature during this period; It is also not proven that the catastrophic volcanism that resulted in the formation of the Deccan Traps was widespread, or that its intensity was sufficient to cause global changes in the climate and biosphere.

Conclusion

Answer the question: “Why did dinosaurs become extinct?” Today there is no certainty. All versions, in the absence of significant evidence, exist only at the level of assumptions. It is worth noting that dinosaurs, probably for the first time in millions of years, were influenced by several of these factors, as a result of which they gave way to mammals.

Video

Sources

http://www.voprosy-kak-i-pochemu.ru/pochemu-vymerli-dinozavry/ http://www.crimea.kp.ru/daily/26123.4/3015794/

Even small children know that dinosaurs became extinct en masse due to a “cosmic gift” - the impressive size of an asteroid or comet. It seems like there is a trace of the fall in South America. And Discovery showed a vivid video reconstruction of the events. Only the hypothesis of a celestial body that genocided the dinosaur population, I personally see as untenable. The reason for the extinction, I believe, lies in the increased gravity of the Earth and the lengthening of the night, which dinosaurs, fortunately for us, were unable to endure.

Let's start with the first question - how could dinosaurs grow to gigantic sizes? In the world of animals of our time, the largest creatures live in the World Ocean, and this is understandable - salt water minimizes body weight, because its density is many times higher than that of air. And on land the only giant is the African elephant, which seems to be huge and massive. But if you compare the weight of an elephant (about 7 tons) with the weight of a diplodocus (about 50 tons), the difference is obvious.

What a colossal load the leg bones of dinosaurs experienced! How could they even move with such mass? Scientists argued for a long time about the reasons for gigantism among dinosaurs and, in the end, decided to draw an analogy with whales - they say, Diplodocus lived in a lake, practically did not crawl onto land and that’s why it was so hefty. For this reason, in reconstruction drawings of the era of dinosaurs, diplodocus is always depicted in a body of water, with the body “immersed in liquid” by 70-80%. But the theory about the aquatic lifestyle of diplodocus and other herbivorous giants that defended themselves from predators with their size does not work. The reason for this: blood pressure.

The difference between blood pressure in the legs and head cannot be excessively high, because... the blood vessels will simply burst. And the larger the animal’s growth, the higher this difference. The tallest giraffe on Earth today is about 5 meters. If you observe the behavior of this herbivore, you will notice: the animal lowers and raises its head very slowly. A giraffe cannot move its head quickly vertically - the pressure will rise sharply and the vessels in its brain will burst. With a neck length of over 6 m, taking into account the size of the body, Diplodocus raised its head 10-15 m from the ground level. In modern conditions of gravity, the blood vessels of a diplodocus would be as thick as a garden hose, otherwise it simply would not survive. But the blood channels in the body of Diplodocus were, in all likelihood, approximately similar in diameter to the vessels in the body of, for example, modern elephants.

So, we’ve sorted out the large dinosaurs, but what about the small ones - why did they become extinct? It's simple - a day in the Mesozoic era was not 24 hours, but approximately 9 hours, i.e. Planet Earth was spinning faster than it is now! Dinosaurs, whose height did not exceed one meter (there were very few of them), depended on air temperature no less than multi-meter representatives of their family - all of them were cold-blooded. It is known that in the Mesozoic the air temperature was 30 degrees and above all year round - the night lasted no more than 3-4 hours, i.e. the air did not have time to cool down. But when the planet's rotation slowed, the average daily temperature dropped by 10 degrees or more. No, dinosaurs did not die out from such a cold snap - they became slower and began to eat less.

Modern warm-blooded animals spend up to 90% of the energy obtained from food to maintain a constant body temperature. Large and small dinosaurs, whose bodies were heated by the sun and air, ate 8-10 times less food than warm-blooded dinosaurs. By the way, during the time of dinosaurs, mammals escaped competition with giants in the reservations of the cold poles of the Earth (which is why they became warm-blooded), where gravity was higher than at the equator. Forced living conditions over millions of years hardened the organism of mammals; they overcame the cooling of the planet’s climate and increased gravity. But dinosaurs don't.

At the end of millions of years of dinosaur reign, their last descendants to walk the earth made a desperate attempt to survive - they grew feathers to maintain body temperature, sharply decreased in size and lightened their bones to cope with the increased gravity. And, it should be noted, the dinosaurs managed not to die out completely - and took to the air, escaping from predatory mammals.

What about sea dinosaurs - why did they all die? Well, they didn’t lay their eggs in the water, but on the shore! Imagine a fish that finds itself on land - it twitches feverishly several times, trying to return to the water, but then calms down. Approximately the same thing happened with marine dinosaurs when they came ashore - their weight became a colossal burden, which means they could not go inland to protect the clutch as much as possible from predators. That is why aquatic dinosaurs became extinct - their numbers decreased year by year, as the offspring were eaten by mammalian predators.

Why did the Earth's gravity increase 3-4 times 170-150 million years ago? Why did the planet’s rotation speed around its axis slow down if in the middle of the Mesozoic a day lasted no more than 9 hours?

Our planet, like other cosmic bodies, is constantly increasing its mass due to cosmic dust and meteorites of various diameters. About 10 tons of dust from the Universe enter the Earth every day. Accordingly, over a million years, cosmic dust increases the mass of the third planet from the Sun by approximately 3650 billion tons. But - if such accumulation of mass occurs constantly and gradually, then dinosaurs would be quite able to adapt to this process. No, something more global and large-scale happened...

In the material “”, I indicated that the collision of our planet with Theia and the acquisition of the Moon happened billions of years ago. Now I'm not sure about this. If we consider the extinction of dinosaurs as a reaction to some mega-scale event, then it is precisely the cosmic accident of two planets. Judging by the thickness of the dust on the Moon - it collects cosmic dust just like any other object in space - the Earth's satellite has been spinning around the planet not so long ago, about 100-150 million years. Agree, a collision of planets has much more significant consequences than the fall of an asteroid with a diameter of 50 km. There is another interesting point - the date of formation of the World Ocean.

It is traditionally believed that the World Ocean appeared on Earth about 4 billion years ago - this date successfully coincides with the basic scientific postulates about the origin of our planet. However, a number of deep-sea drillings of the ocean floor carried out in the last century showed a result that stunned scientists - the age of the rocks forming the ocean floor does not exceed 100-150 million years! It turns out that the collision of the Earth with Theia, the appearance of the Moon and the acquisition of ocean water (it turns out that the bulk of the ocean water came to the Earth from Theia) occurred at approximately the same time. This explains why gravity has increased sharply - the volume of water in the World Ocean is approximately 1.33 billion cubic kilometers. This explains why the rotation of the planet Earth slowed down - the Moon served as a counterweight, and the mass of moving ocean waters became a kind of pendulum, gradually, over the course of millions of years, “adjusting” the day to 24 hours. I note that there have been seas on the planet for billions of years - but this is not an ocean, but just seas (and shallow ones), the area and water volume of which were small.

Dinosaurs are extinct! This is perhaps the only fact about them that all scientists agree on. But there is still debate about the reasons for the disappearance of giant lizards. The popular belief is that their mass death was caused by the collision of a giant asteroid with the Earth. However, there are many other interesting proposals that may complement the generally accepted theory or consider alternative views. Today we will talk about why dinosaurs became extinct.

When did the dinosaur extinction occur?

It should be noted that the extinction was not instantaneous, as some films and television shows usually present to us. Even if we start from the theory of the collision of the Earth with an asteroid, then after that all the dinosaurs did not die immediately, but the process had already been started...

Extinction began at the end of the so-called "Cretaceous"(about 250 million years ago) and lasted about 5 million years (!). During this period, many species and plants disappeared.

However, dinosaurs were the dominant species on Earth for quite a long time - about 160 million years. During this period, new species disappeared and appeared, dinosaurs evolved, adapted to climate change and were able to survive several mass extinctions, until something happened that led to their gradual and final death.

For reference: “Homo sapiens” lives on Earth for only 40 thousand years.

Who survived the extinction?

Climate changes on Earth during the Cretaceous period reduced the diversity of life, but the descendants of many of those species today delight us with their presence. These include crocodiles, turtles, snakes and lizards.

Mammals also did not suffer much, and after the complete disappearance of dinosaurs they were able to occupy a dominant position on the planet.

One may get the impression that the death of living beings on Earth was selective, and that precisely those conditions were formed in which dinosaurs could not survive. At the same time, the remaining species, although they suffered greatly, could continue to exist. These thoughts greatly excite the minds of fans of various conspiracy theories.

By the way, the word “dinosaur” is literally translated from Greek as “terrible lizard.”

Versions of dinosaur extinction

To date, it is still not known for certain what exactly killed the dinosaurs. There are many hypotheses, but not enough evidence. Let's start with the asteroid version, which was greatly popularized and largely distorted by the media and film makers.

Asteroid

In Mexico there is the Chicxulub crater. It is believed that it was formed precisely after the fall of that ominous asteroid that triggered the mass extinction of the dinosaurs.

The asteroid itself caused enormous destruction in the area of ​​its impact. Almost all life in this area was destroyed. But the rest of the inhabitants of the Earth suffered from the consequences of the fall of this cosmic body. A powerful shock wave passed across the planet, clouds of dust rose into the atmosphere, dormant volcanoes awoke, and the planet was enveloped in dense clouds that practically did not let in sunlight. Accordingly, the amount of vegetation, which was a source of food for herbivorous dinosaurs, decreased significantly, and they, in turn, allowed predatory dinosaurs to survive.

By the way, there is an assumption that at that time two celestial bodies fell on our planet. A crater was found at the bottom of the Indian Ocean, the appearance of which dates back to the same time.

Those who like to refute everything question this hypothesis. In their opinion, the asteroid was not large enough to trigger a series of cataclysms. In addition, both before this event and after, other similar cosmic bodies collided with the earth, but they did not provoke mass extinctions.

The version that this asteroid brought microorganisms to the planet that infected dinosaurs also exists, although it is not so likely.

Cosmic radiation

Continuing the theme that it was space that killed all the dinosaurs, it is worth considering the assumption that it led to this gamma ray burst close to the solar system. This happens due to a collision of stars or a supernova explosion. The flow of gamma radiation damaged the ozone layer of our planet, which led to climate change and mutations.

Volcanic activity

We have already mentioned that the asteroid could provoke the awakening of dormant volcanoes. But this could have happened without his participation, and the consequences would still have been sad.

A significant increase in volcanic activity has led to ash in the atmosphere has partially limited the amount of sunlight. And then - the onset of volcanic winter, a decrease in the number of plants and a change in the composition of the atmosphere.

Skeptics have something to say in this case too. Many scientists believe that the changes caused by abnormal volcanic activity were gradual, and dinosaurs had a high ability to adapt, which helped them survive the vagaries of nature. So why couldn't they adapt this time? Unanswered question.

Sharp decline in sea level

This concept is called "Maastricht regression". The only connection between this event and the extinction of the dinosaurs is that everything happened around the same period. In addition, previous great extinctions were sometimes accompanied by changes in water levels.

Food problems

There are two options: either due to climate change, dinosaurs simply could not find enough food for themselves, or plants appeared that killed the dinosaurs. It is believed that they spread on Earth flowering plants, containing alkaloids that poisoned dinosaurs.

Change of magnetic poles

This phenomenon happens periodically on our planet. The poles change places, but the Earth remains for some time without magnetic field. Thus, the entire biosphere becomes defenseless against cosmic radiation: organisms die or mutate. Moreover, everything can last for thousands of years.

Continental drift and climate change

This hypothesis suggests that dinosaurs, for some reason, could not survive climate changes that were caused by continental drift. Everything happened rather prosaically: temperature fluctuations, death of plants, drying up of rivers and reservoirs. It is obvious that the movement of tectonic plates was accompanied by increased volcanic activity. Poor dinosaurs were simply unable to adapt.

Interestingly, rising temperatures may have influenced the formation of dinosaurs in eggs. As a result, only young of the same sex could hatch. A similar phenomenon is observed in modern crocodiles.

Epidemic

Insects preserved in amber can tell scientists a lot of interesting things about ancient times. In particular, it was possible to find out that many dangerous infections began to appear precisely during the extinction of dinosaurs.

We already know that dinosaurs could adapt to climate change, but their underdeveloped immunity could not protect them from a deadly disease.

Theory of controlled evolution

It should be immediately noted that this theory is popular in conspiracy circles. These guys believe that some other intelligence is using our planet as a platform for experiments. Probably this “mind” studied the features of evolution using the example of dinosaurs, but the time has come to clear the experimental site in order to begin the same research, but with mammals in the leading role.

Thus, extraterrestrial intelligence immediately clears the Earth of dinosaurs and begins a new stage of the experiment, the main object of which is us - people! Just some kind of REN-TV. But we have to admit, conspiracy theorists skillfully present everything and do a good job of refuting other theories.

Dinosaurs vs mammals

Small mammals could easily destroy the toothy giants. Scientists do not rule out fierce competition between them. Mammals turned out to be more advanced in terms of survival, it is easier for them to get food and adapt to the environment.

The main advantage of mammals was the difference between their method of reproduction and the method of reproduction of dinosaurs. The latter laid eggs, which could not always be protected from the same small animals. In addition, the small dinosaur needed a huge amount of food to grow to the required size, and food became increasingly difficult to obtain. Mammals were carried in the womb, fed with mother's milk, and then did not need too much food. Moreover, there were always dinosaur eggs under our noses, which could be capitalized unnoticed.

Coincidence of factors

Many scientists are inclined to believe that one should not focus on any one reason, because dinosaurs were very tenacious and over millions of years withstood many surprises from nature. Most likely, climate change, food problems, and competition with mammals are to blame. It is possible that the asteroid became a kind of control shot. All this together created exactly the conditions in which dinosaurs could not survive.

Are humans at risk of extinction?

Dinosaurs lived on Earth for millions of years, people - only a few tens of thousands. During this relatively short period, we were able to create a reasonable society. But this hardly protects us from extinction.

There are quite a wide number of versions of the disappearance of humanity, ranging from global disasters and epidemics, and ending with the same cosmic threat in the form of asteroids and star explosions. However, people today can easily cease to exist - the reserves of nuclear weapons on Earth are more than enough for these purposes... True, some people can still be saved if we have time

For more than 15 years, the University of Tübingen, one of the oldest educational institutions in Germany, has operated the Children's University, where the most curious can get answers to any complex questions from real professors. In order for as many children as possible to learn what modern science is studying, scientists published their lectures in the form of books. Now they are also in Russian. If your child 7-8 years old and older is interested in volcanoes, dinosaurs or knights' castles, these books are a godsend. This time - about dinosaurs for children.

At the beginning of the Mesozoic era, our Earth looked completely different from what it does now. At that time, there was only one continent on the planet - Pangea, washed by a giant ocean. On this palm- and fern-covered supercontinent, new creatures appeared about 243 million years ago - small reptiles that moved deftly on two limbs. We call them dinosaurs.

Dinosaurs looked very different: some wore shells, others had spines, others had horns, and others had long protrusions on their spines that resembled a sail. Some dinosaurs walked on two legs, others walked on four. Some ate meat, others ate plants, and others were omnivores.

About 150 million years ago, these hardy lizards, perfectly adapted to the conditions of their habitat, were the real masters of our planet. And it seemed that nothing threatened them...

The brachiosaurus was as tall as a bell tower and weighed as much as twenty elephants. Supersaurus was more than 30 meters long, which is the height of a 10-story building. The ground shook under the steps of this monster. It seemed that he had no one and nothing to fear. The tyrannosaurus was a real monster: a head the size of a calf, in its mouth there were sharp, long, curved teeth. The Tyrannosaurus had the strongest muscles; even the best runner in the world could not compare with it in speed. None of the modern animals, be it a tiger, a lion or an elephant, would have the slightest chance of coping with him. But who then managed to defeat him?

And yet the fact remains: dinosaurs ceased to exist. During the Late Cretaceous period, many millions of years before the appearance of humans, dinosaurs began to decline in numbers, and about 65 million years ago they completely disappeared.

Many scientists and adventurers went in search of dinosaurs. Over the past century, expeditions have scoured the planet's jungles and other impenetrable areas in hopes of finding at least one surviving fossil monster. But none of these attempts were successful. But the remains of dinosaurs were found in a variety of places. Thus, according to American paleontologist Peter Dodson, 3,000 almost complete dinosaur skeletons are stored in US museums alone. And among them there is not a single one younger than 65 million years old.

It would seem that dinosaurs had no equal in their ability to survive, and they inhabited the planet for an incredibly long time. However, at some point they gave way to another species, whose representatives previously trembled with fear as soon as they saw a dinosaur on their way. These animals, no larger than a cat, benefited when the dinosaurs went extinct. Apparently, their body was covered with fur, and they themselves resembled either squirrels or shrew mice.

Their babies did not hatch from an egg, like dinosaurs, but emerged from the mother's womb, after which the mother fed them with milk. For this feature, scientists called them mammals (mammal is an outdated name for milk) and separated them into a separate class of animals, to which humans belong.

Why did these small, easily vulnerable animals spread throughout the planet, while strong, powerful dinosaurs, on the contrary, became extinct? To answer this question, you must first remember that the extinction of certain species is completely normal and even useful. Anyone who is at least a little familiar with the history of life on Earth understands that modern species of animals did not always live on it: they arose in the process of evolution and someday may disappear. As, for example, this happened with mammoths about ten thousand years ago.

And they are just one of many extinct species. Some species die out without surviving even a couple of million years, while others live on Earth for hundreds of millions. Species leave to make way for others.

In the modern world, humans are primarily responsible for the extinction of species. People hunt, trade rare animals or plants, and destroy their habitats. Every hour three species of plants or animals disappear on the planet; Accordingly, every month the Earth irreversibly loses more than 2,000 species.

What animals were on Earth during the time of dinosaurs?

Apparently, four billion years ago our entire planet was completely covered by ocean. It was here that the first living organisms originated. These were tiny bacteria, green algae and fungi.

And only after many millions of years small fish appeared in the sea. In the Mesozoic era, when dinosaurs already walked on land, the sea still remained more populated, fish of all shapes and sizes frolicked in it: some were as huge as a truck, others had spines growing on their fins, and others were encased in shells. And even then, sharks roamed the ocean.

However, in the Mesozoic era, the land was inhabited by a wide variety of animal species. But she herself looked completely different from how she does now. The five continents familiar to us did not exist, but there was a single giant supercontinent, which scientists called Pangea. Just then, in the Mesozoic, Pangea began to slowly split into two continents: the northern - Gondwana and the southern - Laurasia.

Most of the animals of that era became extinct, but we know of their many descendants. Even before the appearance of dinosaurs, the first beetles and bugs were already crawling on the ground, centipedes reached two meters in length, and dragonflies could boast of wings that were not inferior in size to those of an eagle. Among the few creatures whose appearance has not changed to this day are representatives of the cockroach order, one of the most successful animals in the entire history of life on Earth (this is unlikely to surprise anyone who happened to encounter them in an apartment), because they have existed for more than 300 million years.

Of course, at the beginning of the Mesozoic era, when dinosaurs dominated the planet, nothing foreshadowed that cockroaches would prevail in evolution. A career guidance consultant, if one had existed in those days, would have advised many species to retrain as reptiles, that is, reptiles. After all, it was in front of them at that time that a brilliant future opened up.

Over millions of years, amphibians—that is, those that could live on both land and water—evolved into reptiles, the first vertebrates that no longer needed water. They had a strong skeleton and laid eggs on land. The first of them were relatively small, ate insects and lived in old stumps. But they began to grow quickly.

To get a little idea of ​​what dinosaurs looked like, you can look at a crocodile: the same large mouth, strong chewing muscles, sharp teeth, and a powerful tail. However, crocodiles are not descendants of dinosaurs: both of them descended from the same group of reptiles - archosaurs.

Archosaurs were among the first to try to live on land. Pretty soon there were a few rebels among them, early mammals who began to evolve in a completely different direction. But at that moment no one could have said what this would lead to.

Our knowledge of ancient animals, and especially dinosaurs, comes from professional and amateur scientists who have discovered many remains of extinct organisms over the past 200 years.

Although we are used to talking about dinosaur bones that were dug out of the ground, strictly speaking, these are no longer bones, but stones. But why did animal bones become stones?

The corpses of animals quickly became prey: predators attacked their meat first, then worms and bacteria got to work. Therefore, there was soon nothing left of the soft tissues, be it internal organs, brain or skin.

Even bones and teeth sooner or later begin to decompose in the sun. Although, of course, they are much harder and more durable than other parts of the body, and bacteria will take much longer to destroy them.

But if dinosaur bones fell into the river and ended up under a layer of silt, they were inaccessible to bacteria and thus preserved to this day. Gradually, water began to penetrate into the smallest pores of the bones, filling them with minerals that were formed from salts dissolved in water. Thanks to these substances, over millions of years the bones turned into stones or, as scientists would say, fossils.

Sometimes paleontologists specifically examine the soil in the place where there was a river bed in prehistoric times. After all, this is where you can find dinosaur skeletons.

How do scientists manage to determine with great accuracy how many millions of years old a particular fossil is? It's actually not that difficult. Quite a lot of waste accumulates on Earth: sand dust, lava, plant remains, and animal skeletons. The entire planet's trash settles in layers of sediment.

The deposits of each such layer have their own characteristic features. Let's imagine that hundreds of years later scientists will excavate the site of modern America. At some point, they're bound to start finding lots of Coca-Cola cans and CDs. If there is also a dollar with an engraved date nearby, then we can conclude: if the same Coca-Cola can is found elsewhere on Earth, then the entire layer in which it was found most likely dates back to the 20th century. That is, once they have established the age of a particular layer on any part of the planet, scientists know what time the same layer in any other place on Earth dates back to.

By studying the remains of plants and animals, scientists learn what our planet looked like in prehistoric eras, what the climate was like then: cold or warm, wet or dry, and whether summer and winter were very different from each other. Sometimes they can determine with a high degree of accuracy what the weather was like at one time or another, even if it was millions of years ago. The thing is that both animals and plants are perfectly adapted to their habitat, and their remains can tell us a lot about the nature of that time.

For example, if there are corals in some ancient layer of the earth, then we can say that at the time when the layer was formed, the water was quite warm, because corals can only live in warm water.

So paleontologists have established that there were periods on Earth when the level of carbon dioxide in the air was significantly higher than today. Carbon dioxide is released when burned, and its levels in the atmosphere are now of great concern to environmentalists. Environmentalists fear that carbon emissions from cars and power plants could make the Earth too warm.

But in reality everything is not so simple. Indeed, thanks to paleontologists, we know that in the Cretaceous period the saturation of air with carbon dioxide (carbon dioxide) was higher than in our era. Dinosaurs, by the way, only benefited from this. Since plants need carbon dioxide to grow, ferns, conifers, and cycads (a group of ancient plants that looked like palm trees) reached enormous sizes in those days. And the dinosaurs grew up with them.

Why did dinosaurs become so huge?

The first dinosaurs were relatively small, no larger than a brown bear. Unlike their ancestors, slow amphibians, they could move quite quickly, even the shell with spines did not hinder them much. They owed their mobility primarily to the structure of their body: their paws were located not on the side of the body, but under it (this distinguishes dinosaurs from other reptiles). They walked on their hind legs and were primarily carnivores, feeding on reptiles, amphibians and mammals.

By the time dinosaurs appeared on Earth, mammals had already settled very well on it. Thanks to their coat and ability to maintain a constant body temperature, they were well adapted to the rather cool climate of the next ice age.

But with the beginning of the Mesozoic, the Earth became warmer. At this time, the giant Pangea had already begun to slowly break apart and the warm waters of the ocean rushed into the continent. The ice caps at both poles began to melt, the rains became more frequent, and the temperature crept up. On average during that period it was six degrees warmer than today.

These changes were to the taste of cold-blooded reptiles. After all, the speed of their movement directly depends on the ambient temperature - in the cold they are extremely slow. In addition, with a large amount of solar energy, reptiles no longer need such abundant nutrition as mammals. Those constantly need food to maintain their body temperature; The mammalian body can be compared to a stove, into which firewood must be thrown every now and then so that the fire does not go out.

Of course, this is not the only reason why mammals in the Mesozoic era had to give up the leading place to reptiles, but it was one of the most significant.

Among reptiles, dinosaurs have benefited the most from warming. The number of slow-moving turtles, lizards and crocodiles that walked on four legs did not increase much. At the same time, active bipedal lizards quickly strengthened their positions.

True, their development was also not uniform. For example, the first carnivorous dinosaurs did not have enough food to survive, they devoured each other and eventually became almost completely extinct. Only those who switched to plant food survived.

To grind food in the stomach, they learned to swallow a couple of stones with food each time, since they did not yet know how to chew. And only some of the last dinosaurs acquired massive teeth to grind tough leaves.

The dinosaurs' necks began to lengthen and grow until these giant lizards could easily reach trees and eat leaves right from them. During the Jurassic period, temperatures throughout the planet increased, vegetation became more lush, which means dinosaurs became more obese.

New species of dinosaurs, such as apatosaurs, brachiosaurs, and ultrasaurs, spread throughout the planet. In order not to remain hungry, dinosaurs were forced to eat food for twenty hours a day. If they got hot, they went for a swim. And from time to time they dozed off, basking in the sun.

As for the diversity of species, dinosaurs truly had no equal in this. By 2018, about 1000 genera and about 1200 species are already known. It is believed that the total diversity could reach more than 1500 genera and 2100 species! Scientists have divided these diverse animals into two orders - lizards and ornithischians, differing primarily in the structure of the pelvis.

Thanks to the efforts of paleontologists, a large number of dinosaur eggs were found. They are about the size of a football and quite strong, so the hatchlings had to work hard with their beaks to hatch.

In many nests, many eggs were found lying nearby. This suggested that dinosaurs hatched eggs like birds, and then, like birds, diligently and patiently cared for their offspring. This, by the way, is one of the pieces of evidence that dinosaurs were quite advanced creatures.

The larger the herbivorous dinosaurs reached, the more interesting they were to their other brothers. Thus, a new group of dinosaurs gradually formed and returned to eating meat. And they became more dangerous than all the dinosaurs that lived before them.

These new predators began hunting herbivorous dinosaurs. The largest and most prominent of them was the Tyrannosaurus rex. Presumably it was comparable in size to a one-story house and weighed no less than an elephant. Tyrannosaurus had a giant skull and a small brain. His front paws were extremely small and, most likely, were hardly used. The situation with the teeth was completely different: curved, with small serrations, and on each one you could impale a whole rabbit.

Reptiles lived not only on land, but also in water and even in the air. Ichthyosaurs, similar to giant dolphins, roamed the sea. Mighty pterosaurs flew through the air - their skin resembled the skin of bats.

How these giant animals learned to fly we can only guess. Perhaps the bravest of them once climbed a tree or a rock and jumped from there like squirrels. Only the lightest or those with feathers on their legs and torso managed to survive. And then they passed on the ability to fly to their descendants.