A meteorite crashed 65 million years ago. Analysis of hypotheses about the extinction of dinosaurs. British and French contributions to dinosaur research

Dinosaurs are ancient creatures that appeared on the planet approximately 225 million years ago. For 160 million years, these animals dominated the planet. The period of extinction took about 5 million years, and for about 65 million years they have been absent from the animal kingdom. There are many hypotheses about why dinosaurs disappeared. We will tell you in our article how these animals became extinct and ceased to exist.

The emergence of dinosaurs

Planet Earth was inhabited by different species of plants and animals 3 billion years ago. In the process of evolution, plants and animals appear and disappear, and each such process has its own time period and period. Dinosaurs on the planet lived during the Mesozoic era - the Triassic, Jurassic and Cretaceous periods.

The first simple plants were seaweed, and the first animals were small sea mollusks. The appearance of fish occurred approximately 500 million years ago. About 370 million years ago, the first animals, amphibians, came onto land. Reptiles are a new group of animals that appeared approximately 300 million years ago. The animals had scaly skin, they could lay eggs and be constantly on land. Next in the chain of evolution were dinosaurs. An extinct species of animal gave impetus to the development of such a science as paleontology.

Description of dinosaurs

One of the amazing animals that lived on the planet are dinosaurs. How these large animals became extinct and how they lived can only be judged from their fossilized remains. From the fossil remains it can be concluded that they were reptiles like crocodiles, lizards, turtles and snakes. Dinosaurs range in size from tiny to giant. They had four limbs and a tail. Dinosaurs stood and moved on straight limbs, some on their hind legs, others on all four, and others could move on both two and four limbs. Many dinosaurs had long necks and teeth. Their habitat was significant, but 65 thousand years ago they suddenly became extinct.

Dinosaurs are divided into two groups: saurischians and ornithischians. The difference between the groups is the structure of the pelvic bones. In lizard-hipped dinosaurs the structure of the pelvis is four-rayed, while in ornithischian dinosaurs it is three-rayed. Some species of ornithischians had horns, spines, and shells.

The emergence of interest in dinosaurs

In the 1930s, fossilized remains of dinosaurs were first discovered. Then archaeologists did not attach much importance to them, and only after some time it became clear that these fossils belonged to ancient animals. The very concept of “dinosaur” was introduced by the English zoologist Richard Owen in the mid-19th century. WITH Latin language"dinosaur" is translated as "terrible", "dangerous", "terrible", and from the ancient Greek language - "lizard", "lizard". Since then, interest in these animals has been constantly growing. How many years ago did dinosaurs go extinct? The answer to this question is given by the science of paleontology. Ancient animals are studied by scientists, filmed in films, and become heroes of books. And despite such interest, there is no exact answer to the question of why dinosaurs became extinct.

Age of Dinosaurs

At the end of the Permian period, the formation of a single continent - Pangea. A characteristic feature of this time was global volcanic activity and the disappearance of about 90% of animals. Reptiles adapted best to the new conditions. At the beginning of the Triassic, a group of reptiles called pelycosaurs appeared. By the middle of the Triassic period they were replaced by a group of reptiles called therapsids. In parallel with the therapsids, a new group of reptiles developed - archosaurs. This group of reptiles is the ancestor of all dinosaurs, pliosaurs, crocodylomorphs, ichthyosaurs, placodonts and pterosaurs. The next type of reptile was called thecodont and was adapted to life on land. And it was from them that dinosaurs developed. Extinct animals adapted well and took dominant positions on land, in water and in the air.

During the Triassic period, the following species existed: Coelophysis, Mussaurus and Procompsognathus. Plant dinosaurs developed and evolved.

The largest animals lived in the Jurassic period. In the Late Jurassic period, land animals began to appear - brachiosaurus, diplodocus, etc.

During the Cretaceous period, predatory reptiles began to dominate in the seas and oceans. New species of dinosaurs appear.

End of an era

The Cretaceous period is the heyday of giant lizards, aerial pterodactels and marine reptiles. At the end of the Cretaceous period, a split into Gondwana and Laurasia occurs. The climate on Earth is becoming much colder, and ice caps are forming at the poles. The number of insects appears and increases.

All this led to the extinction of many species of plants and animals, including dinosaurs. They did not die out overnight, but considering that their dominance lasted 160 million years, their disappearance occurred quite quickly. The causes of the disaster that occurred during the Cretaceous period are still unclear.

But did all dinosaurs go extinct? The descendants of ancient reptiles are the crocodiles, lizards and birds that exist today. The first birds appeared during the Cretaceous era, and by the end of the era they already had developed plumage. When the dinosaurs went extinct, birds took over the baton of evolution.

Astrophysical extinction hypotheses

The fall of an asteroid is one of the common versions. The time of its fall coincides with the formation of the Chicxulub crater (Mexico. These events occurred approximately 65 million years ago, during the period when the dinosaurs became extinct. Perhaps the fall of the asteroid led to destructive actions, as a result of which a mass extinction of all living things occurred.

The multiple impact hypothesis states that the asteroid fell several times. In addition to the Chicxulub crater, there is the Shiva crater in the Indian Ocean, which was formed around the same time. This hypothesis explains why the extinction occurred gradually.

There is also a version of a supernova explosion and a comet colliding with the Earth.

Geological and climatic extinction hypotheses

The planet was undergoing significant changes during the period when dinosaurs began to disappear. How animals became extinct is suggested by the theory of changes in average annual and seasonal temperatures. Large individuals need a warm and even climate. Volcanic activity could lead to changes in the composition of the atmosphere and cause a greenhouse effect. A large emission of volcanic ash could provoke a volcanic winter, thereby changing the illumination of the Earth. A significant drop in sea level, ocean cooling, changes in the composition of sea water and a sharp jump in the Earth's magnetic field could also have contributed to the extinction of dinosaurs.

Evolutionary biological hypotheses of extinction

One of the hypotheses of this group adheres to the situation of a mass epidemic. It is possible that dinosaurs were unable to adapt to the changed vegetation, which resulted in poisoning. There is a high probability that the eggs and young will be destroyed by the first predatory mammals. There is also a version that females disappeared during the Ice Age. Scientists have proposed another version of the death of dinosaurs - suffocation: there was a sharp decrease in the amount of oxygen in the atmosphere.

Why did dinosaurs disappear?

Why did dinosaurs disappear? How these became extinct. Various theories and hypotheses provide answers to these questions, but none of them fully answers all the questions. It is known that the extinction of species began long before the moment of the catastrophe, and the astronomical hypothesis in this case is doubtful. Many theories lack actual data, such as the hypothesis of regression of the World Ocean or changes in the magnetic field. Also, the lack of completeness of paleontological data can give a distorted picture.

Combining hypotheses forms a more clear picture. Hypotheses, complementing each other, provide answers to more questions, and the picture of that time looks more drawn and detailed.

The process of evolution - the extinction of the old and the formation of the new - is consistent. And the process of evolution of dinosaurs until the end of the Cretaceous period occurred naturally. But for some reason, at the end of the Cretaceous period, the old species died out, and new ones did not appear, and, as a result, the complete extinction of this species occurred.

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 the flowering plants began to grow and impede the process. The land surface stopped eroding, and nutritional 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 they are closely connected with 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.

It ended, and with it, active tectonic, climatic and evolutionary activity also ended.

Children and dinosaurs

Not only adults, but also children have an interest in ancient animals. Today the project “Why did dinosaurs become extinct?” included in the kindergarten program and primary classes. The uniqueness of such activities lies in the fact that the child independently develops, seeks answers to questions and gains new knowledge. The question of why dinosaurs became extinct is as curious for children as it is for scientists. The interest is primarily due to the fact that these animals are not on earth today and an exact answer to the question of the reasons for their disappearance has not yet been received.

65 million years ago, the asteroid "Heavenly Hammer", whose official name at its location is "Chicxulub", struck the Earth, causing a global environmental disaster, and tore out a page called "Dinosaurs" from the history of the planet. Today, the latest scientific data make it possible to draw up a protocol of that “doomsday” with a high probability. Death came without warning, literally falling out of the blue...

A colossal rock fragment measuring ten kilometers across came from the icy depths of space. At a speed of 150 thousand kilometers per hour, it escaped from the asteroid belt between Mars and Jupiter, where it had peacefully moved in an elliptical orbit around the Sun for billions of years. When the asteroid crossed the orbit of the blue planet, which was at that moment in fatal proximity, it was captured by its gravitational field, slowed down and changed its trajectory...

The solar wind licked and rounded the surface of the giant stone with cosmic dust and frozen gases that had become stuck on during long journeys. Evaporating, they stretched out in a long trail, and now the alien was already visible in the sky even during the day, frozen there as a harmless luminous comma. However, accelerated by the planet’s gravity, it swallowed the last 400 thousand kilometers in an instant. The Earth was reliably protected from smaller guests by a dense, humid atmosphere, where they sometimes burned, sometimes were crushed into small meteor showers, without having time to cause much damage. But for an asteroid of this size, it didn’t matter whether there was atmospheric protection...

Leaving a blinding plasma trail in the clear sky, the “Heavenly Hammer” crashed into the earth’s firmament at a speed of 72 thousand kilometers per hour, or 20 kilometers per second. The fatal geometry of the collision - at an acute angle to the surface - aggravated the already severe consequences of the impact. The earth's crust, especially thick under the continents, withstood the onslaught and even sprung somewhat, throwing the asteroid back.

But in these thousandths of a second, its entire mass, which is two thousand billion tons of stone, has already been converted into energy equal to the simultaneous explosion of five billion atomic bombs, dropped on Hiroshima. Matter turned into a mess of atoms - plasma, a ball of energy released at one point; a flare brighter than the sun illuminated even near space. In the colossal temperature of the explosion (> 10,000 ° C), billions of tons of earthly rock evaporated; a hellish prominence broke through the atmosphere of the doomed planet and stopped only somewhere halfway to the Moon.

From the flash, within a radius of several thousand kilometers from the epicenter, it almost instantly disappeared, all organic matter and some inorganic matter evaporated.

...the first hours

The shock wave, at a speed of 7,000 kilometers per hour, rushed in different directions from the explosion site and circled the globe many times. The wall of incredibly thick dust whipped up by it scattered in concentric circles over thousands of kilometers, suffocating all living things.

At the site of the collision, a so-called “astrobleme” or “star wound” arose - an impact crater with a diameter of 200 kilometers and a depth of 40 kilometers. Its vertical walls, which rose up for several minutes, again collapsed into the boiling magma below. The fall of multibillion-dollar masses of rock caused a colossal explosion of pressure of five gigapascals, as if water had been splashed onto a white-hot frying pan. A hot prominence was thrown high into the atmosphere, containing, in addition to liquid and gaseous stone, megatons of evaporated sea salt and millions of cubic kilometers of water in the form of superheated steam, because half of the crater was located in the Atlantic Ocean.

When the upward movement stopped, hot materials from the explosion fell onto the surface of the planet within a radius of 7,000 kilometers from the epicenter, covering North and South America; a fiery shower ignited vast areas of virgin forests, and the atmosphere began to fill with impenetrable smoke, the likes of which the world had never known.

As a result of the asteroid impact, vibrations arose in the molten semi-liquid core of the planet, generating a tsunami in the oceans more than one kilometer high, which spread from the epicenter in all directions at a speed of 1000 kilometers per hour, broke through hundreds of kilometers deep into the continents, crumbled and washed away all coastal regions.

In parallel to this, vibrations in the bowels of the planet launched a murderous scenario on land: super-strong earthquakes (or rather, “planetquakes”) with a force of at least thirteen shook the globe, collapsing and smashing everything to dust. We are not familiar with such earthquakes today. Shocks of such force were guaranteed to knock down even 80-ton colossi such as the Brontosaurus (in other conditions very stable creatures); they fell into cracks that opened up everywhere and died under collapsing rocks, which is now being discovered during excavations.

... first days

There was no escape from “quick death” in the first moments and hours after the impact, even in the most remote corner of the globe. It turned out that this was only the beginning of a planet-wide hell; life at great distances simply received a reprieve. The survivor was doomed to die in the fire of endless forest fires, thickening the already impenetrable smog with a smoke screen. The “Heavenly Hammer” hit a kilometer-thick layer of limestone and dolomite, a huge mass of these rocks evaporated, and a terrible poisonous cocktail of a mixture of carbon dioxide and sulfur dioxide was brewed in the atmosphere, as in a huge retort.

... the first weeks... months... years...

The cataclysm has entered its “slow” phase. A few days later, the entire sky above the planet was covered with a funeral shroud - a black cloud (however, it would only be seen as black from below). When passing through the atmosphere, the asteroid ripped a colossal “hole” in it, in which a vacuum arose for several minutes. Based on the principle of traction in a chimney, millions of tons of products from the first explosion rushed into this hole, “sucked” by a giant pump to a height of 40 kilometers.

The hole into space had already closed by that moment, and everything remained in the atmosphere. The second explosion after the crater collapse created a second layer of contamination. Everything gradually dispersed around the globe, the water turned into ice crystals, filling the stratosphere by different levels. From the outside, the planet seemed wrapped in a thick cotton blanket, impenetrable to sunlight; A completely dark night reigned on the surface without the slightest hint of a change in time of day. Today this phenomenon is called “nuclear winter”, which would be the consequence of a global nuclear war.

After a brief spike in temperatures due to the asteroid explosion, planet-wide fires, and magma breaking through to the surface, temperatures everywhere quickly dropped to at least 20°C below normal. The surviving plants, including ocean microalgae, stopped growing, the process of photosynthesis was interrupted, and oxygen ceased to flow into the atmosphere. Due to a sharp reduction in evaporation, precipitation almost ceased; the infrequent rains became a poisonous shower, adding to the agony of the survivors.

The heaviest of the survivors, the herbivorous lizards, were the first to die. The predators received a short reprieve, but even for them the short time of abundance, the “feast in the darkness,” quickly ended, because soon there was no one left to eat. Due to the rapid mixing of the ocean, the upper layers of water, rich in oxygen and life, were absorbed by “dead” water of great depths; all the “little things” died out, the food chain collapsed, the sea giants left the historical arena forever.

Almost all those who survived this phase of the disaster died of hunger and cold over the next months, because the black cloud did not disappear, as happens with rain clouds after a rainstorm; it remained in the atmosphere for years, decades, maybe even centuries! The Great Dying took a long time.

Yucatan Sky Hammer Anvil

Today the place of that terrible event is called by the beautiful Spanish-Creole name “Yucatan”. It is known for its wonderful beaches, palm groves, exotic flavor, it is washed by the gentle waves of the Atlantic Ocean - and there are no visible traces of tragedy. The movement of continental plates has long healed the wound inflicted by the asteroid on the Earth; now this place is covered by a kilometer-thick layer of rocks. Is this really the tomb of “Planet of the Lizards”?

The hypothesis of the disappearance of the colossi of antiquity with the participation of a space object is only one of eighty existing theories. This is supported by the discovery of unusually high concentrations of iridium, a rare earth element found only in the Earth's mantle, in the Italian Apennines. It is present almost everywhere on Earth in precisely the layer of clay that corresponds to the time of the death of the dinosaurs.

The theory is also supported by the small oval granules of black glass tektites found almost everywhere, which are a product of the fusion of microportions of sand under the influence of very high temperatures. In layers of clay with a high iridium content there are up to twenty thousand of them per cubic centimeter! This could only happen as a result of a gigantic ejection of deep matter high into the atmosphere, from where they returned to the earth in the form of precipitation.

Their global distribution confirms that the cataclysm that killed the dinosaurs was not a local emergency, but a worldwide event that affected the entire planet. These two finds - iridium and tektites - became the basis for the theory of the American scientist, laureate Nobel Prize Luis Alvarez, which caused a furor in scientific circles in the 80s: dinosaurs became extinct due to an asteroid impact that provoked hyperactive volcanic activity on the planet.

A little later, a curious incident brought evidence of this hypothesis. In 1981, Mexican geologist Antonio Camargo, on behalf of the Pemex oil concern, undertook geological measurements to localize probable underground deposits. He did not find oil, but he discovered a strange anomaly in the Earth’s magnetic field on a circular underground formation invisible from the surface. It was an astrobleme, a colossal crater.

The geologist came to the only correct conclusion: we are talking about the place where a celestial body fell about 65 million years ago. He reported his discovery at a scientific congress in Los Angeles and... created a storm of indignation! “Scientific luminaries”, often being ossified bureaucrats and opponents of everything that does not coincide with their opinion, immediately rejected the point of view of the “non-specialist”; Pemex even threatened to fire him so that he would search for specific oil, and not mythical lizards.

Fortunately, the report was carefully listened to and recorded by a Texas journalist. In his newspaper article, he recalled the hypothesis of another scientist, Luis Alvarez. The story became public and aroused the interest of the scientific world. So the individual pebbles formed a completely realistic picture of the event. The location of the asteroid impact was clearly established: the Chicxulub crater, Yucatan Peninsula, Mexico.

Latest Research

In order to piece together the Big Impact puzzle as accurately as possible, scientists intend to take the crater seriously. To this end, several months ago a group of geophysicists, geologists, paleontologists and impact specialists celestial bodies) started a complex project. Among other things, wells are being drilled to a depth of 1,800 meters; The extracted drill cores are expected to be deciphered using modern methods.

Today's capabilities make it possible to reconstruct with high probability what exactly happened on that day and how. However, all this will take years, according to mineralogists at the Potsdam Center for Earth Geology (Germany), which is responsible for a comprehensive analysis of the crater.

It took life on Earth millions of years to recover from that knockout. Scientists suggest that two-thirds of the earth’s inhabitants died that time; only creatures with a body weight of no more than twenty kilograms, who could still find food sufficient to gain time, managed to survive. Mosses and ferns were the first to return to the devastated regions, followed by other plants, insects and animals.

Those who adapted to a new phenomenon, the cold, had advantages, say, wool. This is exactly what the “weaklings” of that era had - today we call them mammals. The first of them appeared about 200 million years ago, were the size of a mouse, and in the world of giant lizards they were content with the role of universal prey, forced to hide and adapt. New conditions became the beginning of “their era.”

How great is the danger of a new collision between the Earth and an asteroid? According to experts, it is only a matter of time. Scientists have calculated that today a much smaller asteroid would cause such a chain of oscillations in the bowels of the Earth that the resulting tsunamis would wash away the coastal, usually densely populated regions of the planet within a few hours without a trace.

The meteorite that struck fifteen million years ago between present-day Munich and Stuttgart and left a 25-kilometer crater was only one kilometer across, but even this “baby” completely destroyed the then Europe, changing the very geographical contours of the continent. A space object of the caliber of the Yucatan guest would completely destroy today's civilization.

"Big Five" asteroids

There is a version that the source of constant meteorite danger for the Earth is the supposed invisible satellite of our star “Nemesis”. This completely black star moves in an orbit that passes along the outer perimeter solar system, and from time to time it captures cosmic bodies that are dangerously close with its colossal gravitational field, throwing them into our system, where they then collide with one or another planet.

Today, experts agree that the development of life on Earth was determined by five proven collisions of the Earth with space objects, each of which radically changed the conditions of existence on the planet: 65, 200, 240, 360 and 440 million years ago.

So what is still known about the mysterious planet "Nemesis"?

Nemesis (Nibiru) is a dark cosmic body: a protostar, in the depths of which thermonuclear reactions have not begun, and by now has already cooled down, or vice versa, a star that has quickly used up its supply of thermonuclear fuel and by now has also cooled down.

One of the reasons for the hypothesis about the existence of Nemesis was the Stone Age rock paintings depicting two suns.

According to a theory actively discussed in the 1970s and 1980s, the star Nemesis revolves around the Sun in a wide orbit. Approaching the Solar System, Nemesis should create gravitational disturbances in the orbits of the planets, the Earth's magnetic field, and even bring down icy planetoids from the so-called Oort cloud onto the Earth.

It is interesting that the Nemesis hypothesis and its “fatal” name were initially required in order to explain the cyclical periods of mass death of almost all life on our planet. This means that further evidence of the existence of Nemesis in reality could have extremely important consequences for our understanding of not only the history of the Earth, but also our own destinies in the future.

The newly discovered brown dwarf is reported to be just 60 AU (astronomical units) (1 AU = distance from the Sun to Earth) from us and is currently moving towards the constellation Sagittarius. Due to periodic gravitational disturbances in the Oort Cloud, a Spanish team of astronomers calculated that G1.9 travels in an elliptical orbit as it approaches the Sun.

You might ask why astronomers have never discovered this object before. In fact, they discovered it a long time ago. G1.9 was first identified as a "supernova remnant" in 1984 by Dave Green of the University of Cambridge, then after more detailed study by very large telescope NRAO array in 1985, it turned out that the discovered object was unusually small for a supernova.

In 2007, X-ray observations from NASA's Chandra X-ray Observatory revealed that the object was much larger than the last time it was seen! It increased in size by 16%. Puzzled by this observation, Very Large Array repeated its observations 23 years ago and became convinced that it had increased in size. Knowing that a supernova doesn't expand as quickly unless it just explodes, they explained that G1.9 should be a "very young" supernova - no more than 150 years old. But no information about a visible supernova has been found corresponding to this historical period (time Civil War in USA).

Spanish astronomers tracked this object with great interest because they were expecting its appearance. Gravity anomalies have been appearing in the Oort Cloud for some time, suggesting that disturbances were caused by a number of objects with significant mass. G1.9 was recorded to have increased in size even further. This is exactly what they expected, and it proves that an object (Planet X, Nibiru, Nemesis) has approached Earth.

Object G1.9 [above right] is currently positioned toward the center of our Galaxy, Sagittarius, which glows brightly in this infrared spectrum image. Due to the bright background, G1.9 is not visible in normal wavelengths of light.

The image [above] shows evidence that the object grew in size over a period of 23 years. On the left, a blue spherical object was detected in the radio range in 1985 by the Very Large Array. The image on the right shows the same observation point taken in 2008. Obviously the object is larger.

In this image [above] we see the original 1985 photo of the radio emission from the VLA compared to the 2007 photo, this X-ray image taken by the Chandra Observatory.

The image above was provided by the Starviewer team. It shows the object G1.9 on the left and the famous brown dwarf, Gilese 229A on the right. We look for emissions in the microwave range (Starviewer says) that indicate radiated heat from each source. The dark red area is the hottest. Note that the G1.9 has a solid heat output similar to the Gilese 229A. The Starviewer team says this suggests that if G1.9 is truly a supernova, as previously thought, we might expect the spherical region to be larger as hot gas and emissions from the exploding star would be concentrated in the surrounding body .

An example of an infrared scan of the Cygnus-Loop supernova ejecta is below.

There is scientific evidence that the G1.9 brown dwarf is the real cause of climate change. Back in July 2010, Dr. Paul Clark published articles on Science.com regarding this issue, and nearly 700 scientists signed a report on climate change.

StarViewer Team, published the results of her research back in 2009 in a number of journals, as well as on your website. The collected evidence met with an extremely negative reaction in astronomical circles, which in every possible way prevented the acceptance of the discovery and demanded more evidence.

In its statement, Starviewer wrote that NASA would never allow this information to be made public. NASA is fooling people, distracting their attention with all sorts of nonsense, while a small group of scientists is trying to tell the world what is happening and the reason for it.

In their article, Spanish astronomers openly accused NASA scientists of concealing information that there is another massive object in our solar system (twice the size of Jupiter) - a brown dwarf star (official name G1.9), which affects orbits of the planets known to us. That is, in essence, our Solar system is binary. Spanish astronomers claim that all this has long been known to NASA, which is simply leading everyone by the nose, hiding this information from ordinary people.

Why did dinosaurs become extinct?

Dinosaurs, which conveniently went extinct about 65 million years ago, were eerie creatures - thick-skinned, armored, all teeth and claws. For example, Tyrannosaurus rex, the largest land predator of all time, could easily bite a rhinoceros or an elephant in half with one subtle movement of its terrible jaws. And the weight of herbivorous lizards with columnar legs reached 30 and even 50 tons. And it is no coincidence that paleontologists, having unearthed the heavy bones of another antediluvian reptile, called it a seismosaur, that is, a lizard that shakes the earth. The length of this monster, according to cautious estimates by scientists, was 48–50 meters.

For nearly two hundred million years, magnificent reptiles were the absolute masters of all three elements: agile ichthyosaurs, reminiscent of modern dolphins, swam in the primeval seas, multi-ton diplodocus walked the earth, and toothy pterodactyls looked out for prey in the sky. (By the way, the wingspan of these flying monsters could sometimes reach 16 meters, which is quite comparable to the dimensions of a modern combat fighter.)

Tyrannosaurus rex skull

And then suddenly the giant lizards began to rapidly die out, they were replaced by inconspicuous, small and unremarkable creatures leading a predominantly nocturnal lifestyle. Scientists already knew about sudden and catastrophic changes in the composition of the planetary biota at the end of the Cretaceous period in the 18th century, and since then this mysterious phenomenon has often been called the “Great Dying.”

What happened? Usually textbooks paint such a simple picture. A large and prosperous group of reptiles (both predatory and herbivorous), which populated all the ecological niches of the planet, suddenly and unexpectedly died - instantly and everywhere. And since these giants had no serious competitors at that time (mammals huddled on the margins of evolution and subsequently simply occupied an empty house), it is logical to look for some external reason. For example, a climate cataclysm (sharp cooling or, conversely, warming), a supernova explosion, accompanied by deadly fluctuations in the gamma-ray background, or a change in the magnetic poles, which temporarily deprived the planet of its protective shell.

For some time now, the asteroid hypothesis has become very popular. Allegedly, at the end of the Cretaceous period, a huge meteorite crashed onto the Earth, throwing billions of tons of dust into the stratosphere, which screened the surface of the planet, which led to the death of green plants, and after them, the rest of the fauna. In addition, the fall of such a meteorite could provoke a revival of terrestrial volcanism, which significantly aggravated the situation. It should be noted that serious paleontologists do not particularly support this point of view.

Where did the asteroid hypothesis come from? In the mid-1960s, in geological deposits dating back to the Cretaceous-Cenozoic period (approximately 67 million years ago), scientists discovered a layer of blue clay with an abnormally high content of the rare metal iridium (20 times more than the average in the earth's crust). Subsequently, many similar anomalies were found (in some of them the iridium concentration was 120 times higher than the background), and all of them turned out to be the same age - they lay on the Cretaceous-Cenozoic boundary.

Since there is very little iridium in the earth’s crust, and it is found in abundance in meteorite matter (primarily in iron meteorites, which are considered fragments of planetary cores), the American physicist Alvarez associated the iridium anomaly with the fall of an asteroid. He estimated its diameter at 10–12 kilometers and even indicated the location of the disaster - the Yucatan Peninsula, where he managed to find an impressive crater about 150 kilometers in diameter.

The fall of such an asteroid would greatly shake our planet: a tsunami wave of monstrous force and height would devastate the coasts tens and hundreds of kilometers inland, and a huge dust cloud would eclipse the sun for a long time. A six-month absence of sunlight would destroy green plants (photosynthesis processes would stop), and then (along the food chain) animals - both land and sea.

Since Alvarez put forward his impact hypothesis in 1980. impact- “blow”), a lot of time has passed. Today, several dozen iridium anomalies are known, and in geological deposits of very different ages, but it has not been possible to connect them with the mass death of flora and fauna. Moreover, geologists have at their disposal a number of craters much more impressive than the notorious Yucatan. The diameter of some of them reaches 300 kilometers, but nothing serious has happened to the planetary biota (and this has been reliably established). Which is quite natural, since the biosphere is by no means a children’s construction set, the elements of which can be shuffled and folded at random, but a stable homeostat that can effectively withstand various kinds of disturbances.

The famous Russian paleontologist K. Yu. Eskov notes:

In this sense, the situation with the Eltanin asteroid (about 4 km in diameter), which fell in the late Pliocene, about 2.5 million years ago, on the shelf between South America and Antarctica; the remains of an asteroid were recently recovered from a crater formed on the seafloor. The consequences of this fall look quite catastrophic: kilometer-long tsunamis threw marine fauna inland; It was then that very strange burials of fauna with a mixture of marine and land forms appeared on the Andean coast, and purely marine diatoms suddenly appeared in the Antarctic lakes. As for the distant, evolutionarily significant consequences, they simply did not exist (traces of this impact are contained within one stratigraphic zone), i.e., absolutely no extinctions followed all these terrible perturbations.

Thus, the picture that emerges is quite interesting. As soon as iridium anomalies began to be purposefully searched for, it immediately became clear that their strict connection with the mass death of dinosaurs (or any other organisms) was nothing more than an illusion. The fossil remains of Mesozoic dinosaurs clearly indicate that the catastrophic Cretaceous-Paleogene extinction scenario is no good, since some groups of dinosaurs disappeared long before the iridium anomaly, while others sank into oblivion much later. The process lasted for hundreds of thousands and millions of years, so there can be no talk of any rapidity.

Therefore, the asteroid hypothesis, as well as all other “impact” scenarios, can be archived with peace of mind, since they assume the immediate destruction of flora and fauna. Meanwhile, even the mass death of marine organisms at the end of the Cretaceous period (much more rapid than the extinction of dinosaurs) was instantaneous only by geological standards and lasted for a considerable period - according to various estimates, from 10 to 100 thousand years. As for reptiles, they did not become extinct overnight.

K. Yu. Eskov writes:

How so?! It’s very simple: the extinction of dinosaurs continued throughout the Late Cretaceous at a more or less constant rate, but starting from a certain point this decline ceased to be compensated by the emergence of new species; old species die out - and new ones do not appear to replace them, and so on until the complete destruction of the group. (An analogy: a country is losing a war not because the enemy began to inflict unprecedentedly high losses on it at the front, but for another reason - in the rear, tank and aircraft factories stopped due to lack of raw materials.) In other words, at the end of the Cretaceous there was no catastrophic extinction dinosaurs, but the failure of new ones to replace them (this, you see, noticeably changes the picture). This means that we can talk about a rather long natural process.

Alternative versions are no more convincing - for example, the hypothesis of a sudden change of magnetic poles or a supernova explosion near the solar system. Of course, magnetic polarity reversal is a very unpleasant thing, since streams of charged high-energy particles flying from the Sun are deflected in the magnetic field lines, forming onion scales of radiation belts. If our planet’s thick magnetic “coat” is torn off, then hard radiation will begin to freely reach the Earth’s surface.

But, firstly, the leapfrog of the magnetic poles is by no means an exotic, but a natural periodic process, and data from special studies, as a rule, do not reveal a relationship between global biosphere crises and changes in terrestrial magnetism. And secondly, the biosphere as a whole is a flawlessly adjusted homeostat that easily resists any outside interference.

A supernova explosion is a cataclysm on a galactic scale. If such an event occurs in the vicinity of the solar system (according to astronomers, this happens once every 50–100 million years), then the streams of X-ray and gamma radiation will not only destroy the ozone layer, but will also sweep away part of the earth’s atmosphere, provoking the so-called “effect highlands,” which not all organisms can survive. However, even in this case, extinction will most likely not be sudden, but will stretch over tens and hundreds of millennia. In addition, hard radiation and the effect of high altitudes should primarily affect the population of land and shallow waters, but in reality, as we know, the situation was exactly the opposite: flora and fauna suffered the most open sea, including microscopic ones, and among the inhabitants of land, for some reason only dinosaurs became victims of the Great Dying.

This amazing selectivity is generally the most vulnerable point of all impact hypotheses: indeed, why did dinosaurs become extinct, but crocodiles survived and lived safely to this day? Perhaps the unprecedented popularity of various kinds of “impact” versions is mainly due to the successes of observational astronomy over the past 20–30 years.

Since we are busy debunking idle myths, it is necessary to say a few words about the fauna of the Mesozoic. In almost any textbook you can read that the Mesozoic era was the era of dinosaurs, and the Cenozoic is the age of mammals that replaced them. Meanwhile, this is a typical scientific prejudice.

Few people know that mammals were contemporaries of dinosaurs (they appeared on Earth almost simultaneously - at the end of the Triassic) and happily coexisted with them for 120 million years. Moreover, if you sort through the fossil remains of all Mesozoic creatures, you will find that the number of mammal species significantly exceeded the number of dinosaur species. True, our distant ancestors, who vaguely resembled South American opossums, were at that time small and timid creatures, leading a predominantly nocturnal lifestyle.

With certain reservations, the term “Great Extinction” itself can be called a pseudo-scientific myth. And if we are talking about scale, then the Permian-Triassic extinction should be called great - a grandiose biosphere cataclysm that happened at the turn of the Paleozoic and Mesozoic. It was generally the largest in the history of our planet: if at the end of the Cretaceous about a quarter of families disappeared into oblivion, then during the Permian-Triassic extinction, 50% of families, 70% of genera and 90% of species disappeared from the face of the Earth. In addition, all marine ecosystems have changed radically. It would be worth noting that all attempts to link the Late Permian crisis with the asteroid impact ended in absolute failure - no traces of the impact impact could be found in the corresponding horizons.

So what caused the extinction of the dinosaurs? One of two things: either climatic changes at the boundary of the Cretaceous and Cenozoic, or purely “natural” reasons - a radical restructuring within ecosystems and a change in communities.

Let's figure it out in order. We are accustomed to the fact that the planetary climate is characterized by pronounced latitudinal zonality: tropical rainforests grow on the equator, to the south and north of them lie savannas, periodically moistened, where countless herds of ungulates graze, and even further to the north and south there is a strip of sun-scorched deserts and semi-desert. The subtropics give way to temperate forests - deciduous and coniferous, and they gradually give way to the cold tundra, where almost nothing grows. Well, at the poles there is eternal frost and eternal ice.

But it was not always so. The Mesozoic is a classic example of a thermal era, when latitudinal zonation was absent, and the global climate resembled the current subtropical Mediterranean type. In the high latitudes and even at the pole it was warm and quite comfortable, but at the same time it was not too hot at the equator. In short, the temperature gradient - both seasonal and daily - was barely perceptible. But at the end of the Cretaceous, the thermoera was replaced by a cryoera with latitudinal temperature differences.

Dinosaurs were cold-blooded (poikilothermic) animals. Not being able to regulate their body temperature “from the inside,” they were entirely dependent on their environment, but in the even climate of the Mesozoic, this did not cause them much trouble. If the outside heat comes in in abundance, and the impressive dimensions do not allow it to cool down overnight (most dinosaurs were large creatures), then maintaining a high body temperature will not be difficult. And all this without any participation of their own metabolism, on which mammals spend 90% of the energy they consume through food.

This curious phenomenon was called inertial homeothermy (warm-bloodedness), and many scientists believe that thanks to this valuable quality, dinosaurs became the rulers of the Mesozoic. And when the climate changed radically at the end of the Cretaceous, the giant lizards disappeared.

It would seem that we have found the answer, but again something doesn’t add up. Why did dinosaurs become extinct, while other reptiles - also cold-blooded - continue to exist to this day? Why did the Cretaceous crisis affect mainly marine inhabitants, while land creatures survived it calmly? Why did some groups of dinosaurs begin to actively die out long before the fateful calendar date, while others slowly lived out their lives in the Paleogene?

Perhaps it makes sense to look for the answer elsewhere - in the structure of ecosystems? Let us remind the reader about the inconspicuous Mesozoic mammals, which lived side by side with lizards for 120 million years, without interfering with them in any way. These small insectivorous creatures, similar to modern opossums or hedgehogs, occupied their own ecological niche, which no one encroached on. But in the Cretaceous period the situation changed radically.

K. Yu. Eskov describes these events as follows: evolution spurred the sluggish metabolism of primitive mammals and created a “phytophage in a small size class” on this new metabolic basis. (Herbivorous dinosaurs were very large animals.) And if a small phytophage appeared, then a predator would certainly arise, which would not limit itself to hunting close relatives, but would grab everyone within its power. Therefore, a baby dinosaur - a small, defenseless lizard that does not have inertial homeothermy - will instantly become a tasty prey for such a 24-hour active predator.

The version is undoubtedly interesting, but it does not answer all the tricky questions. And here genetics, understood in the broad sense of the word, will come to our aid. Let's talk about marginality as the antipode of narrow specialization, because organic world This is exactly how it develops.

Let us once again remember the Mesozoic mammals, who voluntarily gave up the world to magnificent reptiles and vegetated on the sidelines of evolution. Huddled in remote corners, they were the real outcasts, since they occupied those few ecological niches that the ruling class ignored with magnificent negligence.

The food supply of herbivorous dinosaurs were gymnosperms and ferns, which were widespread in the Devonian. The angiosperm, or flowering, flora, which appeared at the beginning of the Cretaceous period, was forced to settle in the margins, since gymnosperms dominated. Thus, flowering plants were exactly the same marginals as the small Mesozoic mammals. They had no choice but to occupy empty lands where there were no established communities of gymnosperms: landslides, burnt areas, river banks, that is, such biotopes that are usually called “disturbed.” And the species themselves that settle in such conditions are called “coenophobic” by biologists, that is, they are afraid of communities and prefer to exist separately.

However, the tactical loss ultimately turned out to be an important strategic advantage. Firstly, the flowering plants that had settled on the “bad” lands no longer allowed gymnosperms there, and secondly, they had a flower, which played a decisive role in the struggle for existence. If gymnosperms, for the reproduction of their own kind, relied entirely on the wind, which passively carried their pollen, and therefore were forced to settle in clusters, then flowering plants actively attracted insects, which increased their viability by an order of magnitude.

The existence of flowering plants did not depend on the elements, and the angiosperm flora could afford the luxury of living in scattered wastelands. In addition, a new type of flora has learned to form herbaceous forms that not only effectively counteract erosion, but also quickly take over vacant land.

The change in plant communities turned into a real disaster. Contrary to popular belief, not only dinosaurs became extinct, but also 25% of the Mesozoic families of invertebrates - cephalopods and bivalves, single-celled radiolarians, diatoms, foraminifera and other representatives of planktonic organisms. Their calcium shells formed enormous deposits, which is why this period of the geological record was called the Cretaceous.

Thus, yesterday's inconspicuous outcasts - flowering plants and mammals - crushed the dominant fauna and flora of the Mesozoic.

The onset of flowering plants is now commonly called the great angiospermization (from lat. angiospermae- "angiosperms"). When the new type of flora began to decisively predominate, what always happens when the foundation is destroyed: the building simply collapsed. After all, the plant kingdom is precisely the foundation on which the floors of herbivorous animals and predators stand, and they are connected to each other not only by food chains, but also by more complex relationships.

Dinosaurs tried to master a new diet - they developed beaks and powerful dental batteries for grinding highly abrasive food. However, this did not work out well for them, especially in cereal pasture systems, where they obviously lost to ungulates. In addition, herbaceous flowering forms form turf, which reduces erosion and the runoff of organic matter into fresh waters and the oceans, which has dealt a severe blow to marine invertebrate communities.

The thing is that the overwhelming majority of the creatures that inhabited the planet in the Late Cretaceous moved too far along the path of narrow specialization. For the time being, this gave them excellent chances of survival, but every advantage sooner or later turns into a disadvantage. Attachment to gymnosperm communities eventually played a cruel joke on the lizards: when the flowering plants went on the offensive, taking away one territory after another from the previous masters of life, the mammals easily joined the newly formed communities. But dinosaurs were unable to do this and found themselves in an evolutionary dead end, since their adaptive resources had long been wasted. And for marginalized mammals, this turn of events was only to their advantage. Having survived an explosion of speciation under new conditions, they populated the entire planet.

Of course, not only such large taxa as a class of animals or a phylum of plants can be marginal. Individual biological species, as a rule, also do not exhibit complete uniformity across the entire set of characteristics. Moreover: the higher the genetic diversity of a species or population, the greater its adaptive potential. Such a community will almost always find a way to prolong its existence under changed conditions. And even with a stable and measured life, intraspecific marginals can play an important role.

For example, winged individuals are rarely found in populations of wingless water striders. There are very few of them - only 4%. They have genetic differences, but at the same time they can interbreed with their wingless companions and produce offspring. It turned out that these flying degenerates are capable of migrating over fairly long distances, thus ensuring genetic continuity between the water-dwelling population of all water bodies. Four percent of the marginalized population is more than enough to accomplish this task.

It must be said that almost every biological species has, just in case, an emergency reserve in the form of a rare genotype or an unusual form, which allows it to survive difficult times. Let us repeat once again: the genetic diversity of a species or population is the key to its evolutionary success, so the marginalized should be treated not only with respect, but also with care.

So, the emergence and widespread distribution of flowering plants at the end of the Early Cretaceous (about 30 million years before the death of dinosaurs) not only radically changed the structure of continental communities, but also destroyed the Mesozoic dinosaurs, which had lost their plasticity, hopelessly stuck in dead ends of evolution. Of course, climatic disturbances could also play a role, but the key event, the starting point, was almost certainly this fact - the onset of angiosperms.