Meaning) the appearance in the early Cambrian (about 540 million years on the evolutionary scale) deposits of fossils of representatives of many divisions of the animal kingdom, against the background of the absence of their fossils or fossils of their alleged ancestors in the Precambrian deposits.

The theory of evolution has no reliable explanation for this "phenomenon". The theory of creationism sees in this phenomenon another evidence of the failure of the theory of evolution and evidence in favor of Creation.

Discovery history

The discoverer of the Cambrian explosion was the Englishman Robert Murchison, an aristocrat by birth, who, under the influence of his ambitious wife, decided to go into science. Studying the fossils of multicellular ancient eras, and the layers of rocks in which they were located, he encountered a clearly defined boundary, below which there were traces of only the simplest unicellular organisms- bacteria and algae. And a layer above (in the "Cambrian" deposits) - the richest variety of biological forms. Murchison was a devout Christian and shared Linnaeus's belief that "there are exactly as many species as the Creator originally created them". In the open appearance, he saw evidence of the working of God's hand. In the 1830s, Murchison published the results of his research.

Cambrian Explosion and Darwinism

Recent discoveries

For the last hundred years, vertebrates were thought to have appeared later in the history of life. However, in 1999 fish fossils were discovered in Cambrian rocks in China. which confirms that fish appear suddenly in the fossil record along with all other animal phyla. The Cambrian explosion became even louder. For these fully formed fish to appear in the Cambrian, the putative vertebrate ancestor would have to be millions of years back in the Precambrian period, where there are no transitional forms for them or for all the major phyla.

In 2006, in China, geologists discovered a fossil animal embryo that evolutionists believe is 600 million years old. If evolution really happened, then modern embryos, after hundreds of millions of years of evolution, would have to be very different from those found in China. However, the embryos found in China are completely identical to those of modern animals.

In 2008, fossil jellyfish were discovered in the Cambrian beds, which are almost identical to modern living species. Some of them had muscles, a series of stinging cells, complex sex organs and behaviors (including mate recognition and courtship), and compound eyes. According to evolution, while these jellyfish have remained the same jellyfish to this day, during this time (about 500 million years) almost all nature should have evolved - birds, pines, crocodiles, kangaroos, elephants, dogs, flowers, tomatoes, whales, geckos, etc.

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evolution biological Argumentation Terminology The emergence of life History of teaching Criticism and facts

Yastrebov S.A.

("HiZh", 2016, No. 10)

Vendian Prelude

The Snowball Earth era ended 635 million years ago. The last period of the Proterozoic began - the Ediacaran (635-542 million years ago). Now it will be more convenient for us to keep track of time not in billions of years, but in millions - this clearly shows how events are accelerating. Although, perhaps, the point is simply that they are closer to us and have been preserved from them. more traces. Previously, the Ediacarans were called the Vend, in honor of the ancient Slavic tribes - the Veneds (the name of the city of Venice also came from them). Unfortunately, now this beautiful name has been preserved only as a non-strict synonym.

The main event of the Ediacaran (one must add: from our anthropocentric point of view) should be called the appearance of multicellular animals. It is not easy to date this event. In the paleontological record of the Ediacaran there is enough evidence of the transition to multicellularity of the animal type - however, the earlier they are, the more controversial ("Nature", 2014, 516, 7530, 238-241, see also the article by Alexander Markov, http://elementy. ru/novosti_nauki/431720). In the second half of the Ediacaran, vendobionts appear in abundance - large, up to a meter long, mysterious creatures with a flat disc-shaped or leaf-shaped body, consisting of many repeating "segments" of the same type. "Segments" are in quotation marks here because the segmentation of venodobionts almost certainly has nothing to do with the segmentation of true metazoans. The term “vendobionts” itself was coined by the German paleontologist Adolf Zeilacher, who considered these creatures to be a very special form of life - giant multinucleated cells (“Planetary Systems and the Origins of Life", Cambridge University Press, 2007, 193-209). Indeed, there is reason to believe that vendobionts were in many respects closer not to multicellular animals, but to amoeba or fungi (by the way, large multinucleated cells are not uncommon in both of them). They made an attempt to reach a large size, which at first led to success, but ended in failure: at the end of the Ediacaran, the Vendobionts became extinct.

On the other hand, it should be taken into account that the venodobionts were very diverse. It is not a fact that they can be considered at least in some approximation as a single group. It's more of an evolutionary level. And despite the fact that most of the venodobionts did not leave any descendants, modern animals could have directly descended from some of them - for example, lamellar and ctenophores ("Evolution and Development", 2011, 13, 5, 408-414). There is nothing incredible about the Ediacaran roots of these evolutionary branches.

The oldest undisputed fossil multicellular animal is called Kimberella quadrata. This is a bilaterally symmetrical creature up to 15 centimeters long, crawling along the seabed. The nature of changes in the body shape of the found kimberells (and there are many of them found in different parts of the world), together with the imprints of traces, leaves no doubt that they were actively crawling, stretching, contracting and bending with the help of muscles. Characteristic features kimberells - an elongated but compact body with a leg (muscular undersurface) and a mantle (a fold that borders the torso). According to these features, it is very similar not to anyone, but to mollusks (Paleontological Journal, 2009, 43, 601, doi: 10.1134/S003103010906001X). It is believed that Kimberella even had a radula, a “tongue” characteristic of mollusks with chitinous teeth, adapted for scraping algae (PALAIOS, 2010, 25, 565-575, doi: 10.2110/palo.2009.p09-079r). One way or another, this is by all accounts a real multicellular animal.

Kimberella lived 555 million years ago ("Science", 2000, 288, 5467, 841-845). And around the same time, numerous fossil footprints of animals apparently actively crawling along the bottom appear for the first time (“Philosophical Transactions of the Royal Society B”, 2008, 363, 1496, doi: 10.1098/rstb.2007.2232). It should be noted that "true multicellular animals" is not a very strict term; here it is enough to agree that we call animals with muscles, a mouth and an intestine. The Vendobionts, as far as one can judge, had none of this. They ate at best microscopic algae, but most likely just substances dissolved in sea water (“Trends in Ecology & Evolution”, 2009, 24, 1, 31-40). Only at the end of the Ediacaran did multicellular creatures appear that were able to actively search for prey and capture it in large pieces in order to digest it inside. Vendobionts were defenseless before such monsters - it is not surprising that their "golden age" ended there. A completely different era began in the history of benthic communities.

"Big Bang of Life"

The end of the Ediacaran period is at the same time the boundary of two eons - the Proterozoic and the Phanerozoic; and here we need a little explanation. "Phanerozoic" literally means "manifest life". This is the era to which the vast majority of fossils studied by paleontologists belong. All previous times, including the Proterozoic, Archean, and Catarchean, are collectively referred to as the Cryptozoic - "hidden life". Phanerozoic, in turn, is divided into three eras, the names of which are most likely familiar to most of us: Paleozoic, Mesozoic and Cenozoic. "Paleozoic" means "ancient life", "Mesozoic" - "middle life", "Cenozoic" - "new life". Each of these eras is divided into periods. The period from which the Paleozoic (and thus the entire Phanerozoic) begins is called the Cambrian. Like many other geological periods, the Cambrian gets its name from geography: Cambria is the Roman name for Wales, a Celtic country in the west of Britain. Accordingly, a very common synonym for the Cryptozoic is the Precambrian.

In order to correctly see the perspective, let's remember the following: the entire Phanerozoic is (rounded) only about 1/9 of the time of the existence of the Earth, and of the history of life on it. The remaining 8/9 are Precambrian. It is another matter that in the Phanerozoic events are very concentrated.

In 1845, the great Scottish geologist Roderick Murchison suggested calling all the times before the beginning of the Cambrian the Azoic era, that is - literally - lifeless. This name did not last long: already the paleontologists of the 19th century showed that there were traces of life in the thickness of the Precambrian rocks (“The Journal of Geology”, 1927, 35, 8, 734-742). And now we know for sure that life was on Earth during most of the Precambrian, and we can date many key Precambrian events - for example, the oxygen revolution or the emergence of multicellularity.

The main difference between Phanerozoic and Precambrian life is the colossal abundance of multicellular animals, the vast majority of which already belong to modern types. Sponges, ctenophores, coelenterates, all kinds of worms, arthropods, molluscs, brachiopods, echinoderms, hemichordates, and chordates appear in the Cambrian. The sudden appearance of these animals in the fossil record is commonly referred to as the Cambrian Explosion. In older layers, there are no remains of them (at least, they are unambiguously and indisputably determined). The Cambrian is the time of the birth of a fauna close to modern. The Cambrian explosion had such an effect and happened so quickly that it is often called the "evolutionary Big Bang" - by analogy with the very Big Bang in which the Universe was born.

The Cambrian Explosion is also sometimes referred to as the "skeletal revolution". Indeed, many groups of animals that appeared at that moment acquired solid skeletons, and they were completely different and on a different basis: for example, there is literally nothing in common between the spicules of sponges, shells of mollusks and chitinous shells of arthropods. Such simultaneity cannot possibly be accidental. However, the "Cambrian explosion" and the "skeletal revolution" are not synonymous. First, not all Cambrian animals had hard skeletons (for example, the first chordates did not have them). Secondly, even in the Precambrian, obvious skeletal structures are sometimes found - for example, it is not clear who belonged to residential pipes ("Nature", 2006, 2, 37-40). In general, the concept of "Cambrian explosion" is much more specific, and it is not surprising that modern authors often talk about it.

Was there an explosion?

But the question is: was there really a Cambrian explosion? There is an opinion that many modern groups of animals appeared in the deep Precambrian, but for a long time they left almost no fossil remains, and therefore were paleontologically “invisible” (“Science”, 2011, 334, 6059, 1091-1097, doi: 10.1126/science .1206375). The reasons for this could be different: the small size of the animals, their lack of solid skeletons, or simply unsuitable physical conditions for burial. The hypothesis of "long hidden Precambrian evolution" is well supported by molecular systematics, that is, by comparing the amino acid and nucleotide sequences of proteins and genes of different animals (of course, modern ones - neither proteins nor DNA have remained since the Cambrian). Reconstructions made solely on the basis of molecular data often trace the roots of modern animal types not even to the Ediacaran, but to the previous period, the cryogenian (Systematic Biology, 2013, 62, 1, 93-109). Then it turns out that the Cambrian explosion is not so much an evolutionary event as an artifact of preservation. At the turn of the Cambrian, the evolutionary branches of animals simply "manifested", having acquired solid skeletons and began to be buried in sedimentary strata; but they arose much earlier.

However, when molecular biological data are objectively compared step by step with paleontological data, the hypothesis of a “long hidden Precambrian evolution” does not stand up to careful scrutiny (“Current Biology”, 2013, 23, 19, 1889-1895). And it turns out that the Cambrian explosion is not an artifact at all. Most of the major evolutionary branches of animals really arose in the immediate temporal vicinity of the Cambrian boundary (give or take a few million years). There are also mathematical models, confirming that the "trunks" of the evolutionary trees of modern animal types immersed in the Precambrian must be short ("Philosophical Transactions of the Royal Society B", 2016, 371, 1685, doi: 10.1098/rstb.2015.0287). The time of their existence is a matter of millions of years, maybe the first tens of millions, but certainly not hundreds. In general, on this moment we have enough grounds to consider the hypothesis of a “long hidden Precambrian evolution” rather incorrect, and the Cambrian explosion a reality, as this, in fact, follows directly from paleontological data.

To weaken the categoricalness, we add: the conclusion that we have just made, of course, has the property of falsifiability. This means that it is possible to formulate clear conditions under which it will be refuted. For example, for this it is quite enough to find at least one reliably identifiable scorpion (or centipede, or snail) of cryogenian age. But so far this has not happened, and the likelihood that this will ever happen is decreasing every year.

Causes of the explosion

So, at the beginning of the Cambrian, many new large evolutionary branches of animals arose uniquely quickly. This has never happened again, before or since. Even after catastrophic mass extinctions (which will be discussed later), the animal world was restored due to the increase in the diversity of large groups that already existed, and not due to the appearance of new ones. That is why the Cambrian explosion necessarily requires an explanation.

True, “quickly” does not mean “instantly”. New groups of animals do not appear all at once in full force, like actors after the curtain goes up. The Cambrian explosion was, though highly compressed in time, but still gradual; the rate of evolutionary processes in it can be measured, and there are such studies. The Cambrian lasted approximately 57 million years (542-485 million years ago), while at the very beginning (the first six million years) the marine fauna is still quite poor. New groups of animals appear there really quickly by the standards of the history of the Earth, but not instantly.

What was it all about? In the century and a half that has passed since scientists (including Charles Darwin) realized the mystery of the Cambrian explosion, a variety of explanations for this event have been proposed, from genetic to cosmic. One modern review article on this topic is called “Beyond the Cambrian Explosion: From the Galaxy to the Genome” (“Gondwana Research”, 2014, 25, 3, 881-883, doi: 10.1016/j.gr.2014.01.001 ). For example, the trend towards the mass formation of mineral skeletons - the famous "skeletal revolution", it is also "biomineralization" - at the beginning of the Cambrian embraced not only a wide variety of multicellular animals, but also unicellular eukaryotes, and some algae. This suggests that this is due to a global change in the chemical composition external environment, that is, in this case, sea water. Indeed, it has been shown that at the beginning of the Cambrian, for some purely geological reasons, the concentration of calcium (Ca2+) in seawater, an ion that is needed to create solid skeletons like no other, increased by about three times (Geology, 2004, 32, 6, 473-476). The mineral basis of animal skeletons is most often calcium carbonate (shells of mollusks, needles and cups of coral polyps, sponge spicules), and sometimes calcium phosphate (bones of vertebrates).

The problem is that explaining the skeletal revolution is not the same as explaining the Cambrian explosion itself. The skeletal revolution merely supplied hard, mineralized tissues to a number of animals that already existed at the time it began. And it didn't even apply to all of them. In those Cambrian localities, the type of preservation of which allows the burial of non-skeletal creatures, it is immediately found that a considerable part of the Cambrian fauna was quite “soft-bodied”. So it's not about the skeletons. The phenomenon that must be explained first of all is the unique acceleration of the evolution of multicellular animals, which very quickly (at the end of the Ediacaran - the beginning of the Cambrian) created many new large groups, whether skeletal or not.

In the following story, we will proceed from the scenario that was briefly outlined back in the early 1970s by the American paleontologist Stephen Stanley. Of course, paleontology is a very rapidly developing science; forty-year-old works in it always require amendments, and we will introduce these amendments in the course of the conversation. True, in fact, it will be more of an addition. Stanley's main idea has stood the test of time exceptionally well. The sum of the facts known so far fits into it perfectly.

Start over. In parentheses, we note: to decide what exactly should be taken as the “beginning”, when parsing any historical process is not an easy task, because cause-and-effect chains can stretch into the past almost indefinitely, confusing a careless researcher. In our case, the "beginning" will be the Ediacaran biota. What did she represent?

In ecology, it is customary to single out environmental-forming organisms, the activity of which determines the structure of entire communities. Such organisms are called edificators.

For example, in a modern oak forest, the edificator is oak, in a small quiet pond it may well be duckweed, etc. So, in the Ediacaran seas, the edificators were the “carpets” of filamentous algae covering the bottom - the so-called algal mats (PALAIOS, 1999, 14, 1, 86-93, doi: 10.2307/3515363). On these "carpets" lived already familiar to us vendobionts. Most of them led an attached lifestyle; how they ate is not entirely clear, but most likely - visually, sucking dissolved substances from the water with the entire surface of the body. Some marine protozoa still feed in this way, for example, large ones - up to 20 centimeters! - multinuclear xenophyophores, similar to giant amoebas. Vendobionts could well be close to them in terms of lifestyle.

There are other versions. In 1986, paleontologist Mark McMenamin suggested that vendobionts were ecological analogues of modern pogonophores - deep-sea annelids devoid of a mouth and intestines. Pogonophores live in the ocean at a depth where sunlight does not penetrate. But there are hot springs that release hydrogen sulfide (H 2 S) into the water. The body of the pogonophora is stuffed with symbiotic bacteria that oxidize hydrogen sulfide to sulfur and the resulting energy is used to fix carbon dioxide, as in photosynthesis. This process feeds both the bacteria and the worm in which they live. It was easier for Vendobionts: they often lived in shallow water, where there was enough sunlight for photosynthesis, and they could well feed on the symbiotic unicellular algae that filled their body. This is also quite real, there are modern worms and molluscs that do just that - however, for them this source of food is additional. But why shouldn't it be the main one? The world of the Vendobionts, where no one ate anyone, McMenamin called the "Garden of Ediacara", with an obvious jocular allusion to the Garden of Eden (PALAIOS, 1986, 1, 2, 178-182, doi: 10.2307/3514512). The great disadvantage of this hypothesis is that it is still difficult to test; moreover, it obviously cannot apply to all venodobionts without exception - some of them lived in the sea deeper than the level where enough light penetrates for photosynthesis (“Proceedings of the National Academy of Sciences USA”, 2009, 106, 34, 14438-14443 ). But, in the end, in different conditions, they could eat differently.

The paradox is that the concept of the "Garden of Ediacara" seems to be close to the truth with any realistic assumption about the mode of nutrition of vendobionts. It does not really matter whether algae lived in them or not. In the Ediacaran world, no one really ate anyone (except for single-celled objects, but single-celled eukaryotes can devour each other themselves). It is of fundamental importance that up to a certain point in the Ediacaran communities there were not only predators (who would eat other animals), but also “herbivores” (who would scrape off algae or otherwise actively eat them). Thus, no one interfered with the growth of algal mats.

That all changed when an increase in the oxygen concentration in sea water (which, according to geological data, was gradual throughout the Ediacaran) allowed some multicellular creatures to speed up their metabolism enough to start to really active image life. “Harvesters” appeared - large animals with a motor system and a mouth, which moved along algal mats and ate away large areas of them. One of these "pickers" was the kimberella familiar to us. In terms of lifestyle and speed of movement, the first Ediacaran algae-eating animals most likely resembled modern snails; for us it looks harmless, but "from the point of view" of the Ediacaran inhabitants, the appearance of such creatures was a real disaster. The seaweed mats immediately ceased to be solid; animals not only scraped them from above, but also ate from below, having mastered penetration into the ground for this (zoologists call such actions "mining"). Here the vendobionts also got it, which at the end of the Ediacaran simply disappeared.

From that moment, a general pattern began to work, established by ecologists a long time ago and tested in various ways, up to direct experiments: under the pressure of a predator, the diversity of its prey increases compared to a community where there are no predators at all (“Proceedings of the National Academy of Sciences USA” , 1973, 70, 5, 1486-1489). If earlier benthic communities were saturated with very few dominant species of algae, now the balance has collapsed and rapid evolution has begun. Meanwhile, the set of ecological niches available to animals was also expanding. Active ground beetles appeared, adapted to constantly live in burrows, passing the bottom soil through the intestines and extracting nutrients from it; this is how many sea worms still live - sandworms, for example. For the first time, earth-eating worms began to dig not only horizontal, but also vertical passages in the seabed, causing the soil to be enriched with oxygen and thereby further facilitating its colonization by other animals. These events have been called the "substrate revolution" (GSA Today, 2000, 10, 9, 1-7, ftp://rock.geosociety.org/pub/GSAToday/gt0009.pdf). Thus, evolving animals not only occupied ready-made ecological niches, but also actively created new ones, turning the process into autocatalytic (self-accelerating).

Some inhabitants of the bottom surface began to expand their ecological niches not towards the ground, but, on the contrary, towards the water column. As a result, zooplankton arose - a community of small animals that are suspended in water and drift along with it. As a rule, representatives of zooplankton feed by filtering water and straining phytoplankton from it, that is, unicellular algae located in the same water column (there were already as many of these by the time of the Cambrian explosion). And indeed, in the early Cambrian, the first planktonic filter feeders appeared in the paleontological record - branchiopods ("Paleobiology", 1997, 23, 2, 247-262). Gills, like all crustaceans, are owners of jointed limbs, originally intended for walking on the ground, that is, along the bottom. Therefore, there is no doubt that early stages they spent their evolution at the bottom, and turned to the planktonic way of life only later.

The consequences of the appearance of zooplankton turned out to be global. The fact is that plankter animals filter out not only algae from the water, but also any suspension in which there may be at least some nutrients. These are mainly scattered remains of dead organisms. After filtering the suspension and sucking useful molecules out of it, plankters (primarily crustaceans differ in this) carefully “pack” the rest in their intestines into dense lumps - fecal pellets that quickly sink and go to the bottom. Pellet suspension transportation - the most important factor, which reduces the turbidity of the water in the ocean. Thus, after the appearance of planktonic filter feeders, the water became transparent, light penetrated it to a greater depth, and the concentration of oxygen in it increased (part of it was previously spent on the oxidation of the same dead suspension). The first factor increased the depth of the zone in which photosynthesis is possible, the second improved the conditions for the benthic fauna. According to all data, the transparent oxygenated Phanerozoic ocean differs sharply from the muddy Precambrian ocean (“Geobiology”, 2009, 7, 1, 1-7). At the same time, the concentration of oxygen in the atmosphere also increased. Naturally, under the new conditions, the diversity of both plants and animals increased further. Another autocatalytic loop is closed.

The coming of the predator

All the animals we've talked about so far have been "herbivores" in the broadest sense. They ate either photosynthetic organisms, or, at worst, someone's dead remains. At the same time, the own biomass of "herbivores" was a valuable (and until some point completely unclaimed) resource for animals that feed on other animals, that is, for predators. At first, no predators simply existed. But in the presence of such attributes of active life as the nervous system, muscles and oral apparatus, their appearance was only a matter of time. The first large predators, already quite definitely specialized in feeding on other multicellular animals, appear about 520 million years ago; these are dinocarids - well-swimming creatures related to arthropods ("Gondwana Research", 2014, 25, 896-909, doi, 10.1016/j.gr.2013.06.001). The most famous representative of dinocarids is anomalocaris, a slender, segmented creature about a meter long with complex faceted eyes and powerful jointed near-mouth limbs that clearly served to capture moving prey. At the very beginning of the Cambrian, there were no such predators. The "Skeleton Revolution" was undoubtedly in some way a response to their appearance; changing the chemical composition of sea water only made it easier. And the appearance of skeletons, in turn, launched the development of new ecological niches. Stephen Stanley quite rightly wrote that to explain the Cambrian explosion, a purely biological causes; factors acting on the biosphere from the outside could affect the rate of this or that process, but all the main events can be explained without them. The explosion of multicellular animal diversity was the natural result of a series of autocatalytic processes set in motion by the appearance of the first "herbivores" (like Kimberella) and occurring at the level of communities, in other words, ecosystems. Outside of ecology, it is really impossible to explain the Cambrian explosion.

With the advent of predators, the process of formation of new life forms began to slow down a little. A repertoire of ecological niches has developed, almost all of them have already been distributed and occupied. Of course, the expansion of communities continued further - just more slowly. For example, only after the end of the Cambrian period did spadefoot mollusks appear, occupying a rather exotic niche of burrowing predators (“Advances in Marine Biology”, 2002, 42, 137-236). But such a scale as at the turn of the Ediacaran and Cambrian, the large-scale evolution of animals never again reached.

From the point of view of the event history, the beginning of the Cambrian explosion can be considered the appearance of the first effective algae eaters (kimberella), and the end - the appearance of the first effective predators (anomalocaris). Kimberella appeared 555 million years ago, anomalocaris - 520 million years ago, the interval between them is 35 million years. Not so fast.

They arose on the border of the Cambrian almost suddenly, not being descendants of a pre-existing fauna.

However, other studies, both dating back to the 1970s and later, noted that complex animals similar to modern species arose long before the start of the Cambrian. In any case, numerous evidence in favor of the existence of life long before the Cambrian removed from the agenda the question of the "Cambrian explosion", as a phenomenon of the sudden emergence of life.

The question of the causes and mechanisms of the next increase in the complexity and diversity of life forms on the border of the Cambrian, which are not descendants of the disappeared Hainan and Vendian biota, remains open. To date, the problems of the "Cambrian explosion" are focused on two key issues:

• whether there really was an "explosive" increase in the diversity and complexity of organisms in the early Cambrian, and
• what could be the reason for such a rapid evolution.

Information sources

Building an accurate chronology of events at the boundary between the Precambrian and the Early Cambrian presents a significant difficulty. Because of this, the description of the sequence and interrelationship of certain phenomena in the framework of the discussion of the Cambrian explosion should be considered with some caution.

In addition to problems with dating, the study of events at the Cambrian boundary is hampered by the lack of paleontological material itself. Unfortunately, the further the period under study is from us, the less accessible its fossils are for studying. Among other things, the reasons for this are:

Remains of living organisms

Along with fossils, Cambrian deposits contain an unusually high number of deposits that have preserved imprints. soft parts bodies of various organisms. Such prints allow us to study in detail animals that are not preserved in the form of fossils, as well as internal organization and the functioning of organisms, which are usually represented only by shells, spines, claws, etc.

In the Cambrian, the most important deposits are: Early Cambrian

Middle Cambrian

and Upper Cambrian deposit

• Orsten (Sweden).

Although all these deposits have excellently preserved the anatomical details of organisms, they are far from perfect. Most of the Cambrian fauna may not be represented in them at all, since the deposits were formed under specific conditions (landslides or volcanic ash, which very quickly retained the soft parts of the bodies). In addition, the known deposits cover only a limited period of the Cambrian and do not cover the critical time immediately before it begins. Since well-preserved burials are generally rare, and fossil deposits extremely rare, it is highly unlikely that they represent all types of organisms that have existed.

Fossilized footprints left by living organisms

Fossilized footprints consist mainly of paths and burrows left on the seabed. Such tracks are extremely important because they provide the researcher with data on organisms whose bodies have not been preserved in fossils. Often, only they make it possible to study organisms belonging to a period from which the remains of animals capable of leaving such traces have not been preserved. Although an exact correlation of traces with the organisms that left them is usually impossible, tracks may provide the earliest evidence for the existence of relatively complex animals (like earthworms, for example).

Geochemical observations

In geological rocks belonging to the lower boundary of the Cambrian and its beginning, strong fluctuations in the isotopic composition of three elements are noted - strontium (87 Sr/ 86 Sr), sulfur (34 S/ 32 S) and carbon (13 C/ 12 C).

• mass extinction. Mass extinctions of organisms should directly increase the proportion of the 12 C isotope in sediments and thus reduce the 13 C/ 12 C ratio.
• Release of methane. In permafrost and on the continental shelf, methane molecules produced by bacteria are trapped in a "cage" of water molecules, forming a mixture called methane clathrate. Being produced by living organisms, this methane is enriched with the 12 C isotope. As the temperature rises or falls atmospheric pressure, the clathrates break up. This decay releases stored methane enriched in carbon-12 into the atmosphere. In the atmosphere, methane is converted to carbon dioxide and water, and the carbon dioxide reacts with minerals to form carbonaceous rocks with an excess of carbon-12. As a result, the isotopic composition of geological deposits shifts towards 12 C.

Comparative anatomy

Cladistics is a method of constructing an "evolutionary tree" of organisms, most often by comparing their anatomical structure. With the help of such an analysis, both modern and fossil organisms can be compared with each other in order to establish the course of their evolution. In a number of cases, it can be concluded that group A must have appeared before groups B and C, since they are more similar to each other than to A. By itself (without correlation with paleontological excavations), this method does not say anything about the time when changes occurred, but it is able to restore the sequence of the evolutionary development of organisms.

Molecular phylogenetics

Paleontological evidence

In this section, the main evidence is ordered by the time of formation of the deposits in which it was found, since dating is a central issue in the study of the Cambrian explosion. At the same time, one should keep in mind the ambiguity of the chronology of fossils belonging to this period.

The review of finds begins from a time long before the Cambrian and ends in the early Ordovician, since there is an opinion that the formation of the main types of modern fauna began before and ended after the Cambrian.

Molecular phylogenetic data (1.2 - 0.5 Ga)

There is still ongoing debate regarding the chronological interpretation of molecular phylogenetic data:

In any case, the data of molecular phylogenetics suggest that the formation of the main types of animals was a very long process, far beyond the 10 million years (about 543-533 million years ago) of the "Cambrian explosion".

Precambrian traces of metazoans

There is both indirect and direct paleontological evidence that multicellular organisms first arose long before the start of the Cambrian.

Decline of bacterial mats (1.25 Ga)

Precambrian stromatolite

modern stromatolites. Western Australia.

Stromatolites form an important part of the fossil record from about 3 billion years ago. Their heyday falls on a period of 1.25 billion years ago, after which they began to decline (both in total number and in diversity). By the beginning of the Cambrian, this reduction was already about 20%.

The most common explanation for the decline is the assumption that the microorganisms that make up the bacterial mats were preyed upon by other living organisms (which should indicate the existence of rather complex predators already about 1 billion years ago). This assumption is confirmed by the observed anticorrelations between the diversity and abundance of stromatolites, on the one hand, and the richness of marine fauna, on the other. Thus, the repeated decline of stromatolites occurred in the late Ordovician - immediately after another "outbreak" of the diversity and abundance of marine fauna. During the Ordovician-Silurian and Permian-Triassic extinctions, the recovery of stromatolites was again observed - with subsequent declines as the marine fauna recovered.

The development of means of protection among akritarchs. Early predation (1 Ga)

Acritarchs are fossilized fossils of an indeterminate nature, usually the shells of cysts of unicellular and multicellular algae. For the first time they are found in deposits dating back to 2 billion years ago.

About 1 billion years ago there was a sharp increase in their number, diversity, size, anatomical complexity and, especially, in the number and types of spines. The number of architarchs sharply decreased during the global glaciation, but subsequently recovered with the achievement of maximum diversity already in the Paleozoic.

Their exceptionally spiky forms, dating back to 1 billion years ago, may indicate the existence of predators already then, large enough to crush them or swallow them whole. Other groups of small Neoproterozoic organisms also have some form of defense against predators.

Traces left by multicellular organisms (1 billion years)

In India, sediments dated 1 billion years ago contain fossils that may be traces of organisms moving through and through soft rock. The traces found were apparently left directly under a layer of cyanobacterial mats that covered the seabed. The researchers concluded that the tracks owe their appearance to the peristalsis of three-layered multicellular organisms up to 5 mm in size - in other words, animals whose diameter was comparable to that of earthworms, and possibly had a coelom. Other researchers believe that these and similar finds older than 600 million years were left not by living organisms, but by physical processes.

Multicellular embryos from Doushanto (632-550 Ma)

However, the discovery in 2007 of embryos surrounded by a complex shell (in rocks aged 580-550 million years) indicates that the fossils in Doushanto are nothing more than resting eggs of multicellular invertebrates. Moreover, it became clear that some of the acritarchs found in the earlier rocks of Doushanto (632 Ma) actually represent shells of such embryos.

Another fossil from Doushantuo - Vernanimalcula(from 0.1 to 0.2 mm in diameter, age about 580 million years) - is considered by a number of scientists as the remains of a three-layer bilateral organism that had a whole, that is, an animal as complex as earthworms or mollusks. Despite doubts about the organic nature of these fossils, since all 10 specimens found Vernanimalcula are of the same size and configuration, it is unlikely that such uniformity is the result of inorganic processes.

The most recent Doushantuo deposits also show a sharp drop in the 13C/12C carbon isotope ratio. Although this change is worldwide, it does not coincide with other major events such as mass extinctions. A possible explanation is " chain reaction» the interrelated evolution of organisms and changes in the chemical composition of sea water. Multicellular organisms, actively absorbing carbon from water, could contribute to an increase in the concentration of oxygen dissolved in sea water, in turn, providing the emergence of new multicellular organisms (such as Namapoikia).

Ediacaran fauna (610-543 Ma)

spriggin

Multicellular fossils of the Ediacaran period were first discovered in the Ediacaran Hills in Australia, and then in deposits from other regions: Charnwood Forest (England) and the Avalon Peninsula (Canada). These fossils are 610-543 million years old (the Ediacaran period precedes the Cambrian). Most of them measured several centimeters and were significantly larger than their predecessors. Many of these organisms have no analogues with any of the species that lived before or after the Ediacaran period. It has been suggested that the most “strange” representatives of the Ediacaran fauna should be assigned to a separate kingdom - the “Vendozoa” (Vendozoa). It is among them that charnia is included - the most ancient of the finds of the Ediacaran period (age - 580 million years).

However, some Ediacaran organisms may turn out to be the precursors of later fauna:

Holes in sinks Cloudina. Selection in the "predator-prey" system

In some places up to 20% of fossils Cloudina contain holes with a diameter of 15 to 400 microns left by predators. Some Cloudina were damaged several times, which indicates their ability to survive attacks (predators do not re-attack empty shells). very similar to Cloudina fossils Sinotubulites found in the same burials do not contain holes at all. Such selectivity may indicate the existence already in the Ediacaran period of evolutionary selection of size classes, as well as specialization of prey in response to predation, which is considered as one of the causes of the Cambrian explosion.

Increasing diversity of traces left by organisms (565-543 Ma)

The earliest Ediacaran fossils, dating back to 610-600 million years ago, contained only traces left by cnidarians. About 565 million years ago, more complex traces appear. To leave them, the organisms required a skin-muscular pouch, and their general structure was to be more complex than that of cnidarians or flatworms.

Just before the beginning of the Cambrian (about 543 Ma), many new tracks appear, including upright burrows. Diplocraterion and Skolithos), as well as traces of possible arthropods ( Cruziana and Rusophycus). Upright burrows suggest that worm-like animals have acquired new behaviors and possibly new physical abilities. Traces Cruziana and Rusophycus talk about the existence of an exoskeleton in the immediate predecessors of arthropods, although perhaps not as rigid as later.

Cambrian fossils

Shell fauna (543-533 Ma)

Fossils known as "small shelly fauna" (eng. small shelly fossils) have been found in different parts of the world and date back to the end of the Vendian (Nemakit-Daldynian Stage) and the first 10 Ma since the beginning of the Cambrian (Tommotian Stage). These include a very diverse collection of fossils: needles, sclerites (plates of armor), tubes, archaeocyates (a group of sponges or animals close to them), as well as small shells, very reminiscent of brachiopods and snail-like molluscs, although very small (1-2 mm in length).

Early Cambrian trilobites and echinoderms (530 Ma)

Fauna Sirius Passet (527 Ma)

The most common fossil of the Sirius Passet Greenland burial is arthropods. There are also a number of organisms with solid (mineralized) body parts: trilobites, chiolites, sponges, brachiopods. Echinoderms and mollusks are completely absent.

Sirius Passet's most bizarre organisms were Pambdelurion and Kerygmachela. Their long, soft-segmented bodies, with a pair of broad "fins" on most segments and a pair of segmented appendages at the back, make them similar to anomalocarids. At the same time, the outer parts of the upper surface of the "fins" had corrugated surfaces, which can be gills. Under each "fin" there is a short boneless leg. This structure allows you to associate them with arthropods.

Chengjiang fauna (525-520 Ma)

Haikouichthys - reconstruction

Anomalocaris - reconstruction

Hallucigenia - reconstruction

This fauna has been described from several fossil sites in Chengjiang County (Yuxi City, Yunnan Province, China). The most important is Maotianshan shale- a burial in which fossils of soft-bodied animals are very well represented. The Chengjiang fauna belongs to the period 525-520 million years ago - the middle of the Early Cambrian, several million years later Sirius Passet and at least 10 Ma predates the Burgess Shale.

The body parts of the most ancient chordates (the type to which all vertebrates belong) were found in the fossils:

Representatives of groups close to arthropods were found in the same deposits:

These organisms probably belong to the group Lobopodia, to which of the modern groups the Onychophora belong.

About half of the Chengjiang fossils are arthropods, some of which had hard, mineralized exoskeletons, like most later marine arthropods. Only 3% of organisms had hard shells (mostly trilobites). Representatives of many other types of animals have also been found here:

• Priapulids (burrowing sea worms - ambush predators);
• Bristle-jawed (marine invertebrates that are part of plankton);
• Ctenophores (intestinal, outwardly similar to jellyfish);
• Echinoderms (starfish, sea cucumbers, etc.),
• Chiolites (mysterious animals that had small conical shells),

Early Cambrian crustaceans (520 Ma)

Burgess Shale (515 Ma)

Main article: Burgess Shale

Marrella

Pikaia - reconstruction

The Burgess Shale is the first known large burial site of the Cambrian period, discovered by Wolcott in 1909. The reanalysis of fossils by Whittington and his colleagues in the 1970s formed the basis of Gould's book " amazing life”, which opened the Cambrian explosion to the general public.

Among the Burgess fossil slates, arthropods are the most common, but many of them are unusual and difficult to classify:

Opabinia - reconstruction

Wiwaxia - reconstruction

In addition, samples of exotic organisms are presented in the burial:

Emergence of new ecosystems and types after the Cambrian

Due to a major extinction at the Cambrian-Ordovician boundary, typical Paleozoic marine ecosystems were formed only during the subsequent recovery of marine fauna. The earliest fossils related to bryozoans are also first discovered in the Ordovician period - well after the "Cambrian explosion".

findings

The long process of the emergence of multicellular

In Darwin's time, all that was known about fossils suggested that the main types of metazoans arose and formed within only a few million years - from the early to middle Cambrian. Until the 1980s, these ideas were still valid.

However, recent finds suggest that at least some three-layer bilateral organisms existed prior to the beginning of the Cambrian: Kimberella can be considered as early mollusks, and scratches on rocks near these fossils suggest a mollusk-like feeding method (555 million years ago). If we assume that Vernanimalcula had a three-layer bilateral coelom, this pushes back the emergence of complex animals by another 25-50 million years ago. Shell Hole Detection Cloudina also suggests the presence of advanced predators at the end of the Ediacaran period. In addition, some traces in fossils dating back to the mid-Ediacaran period (about 565 million years ago) could be left by animals more complex than flatworms and having a skin-muscular sac.

Long before this, the long decline of stromatolites (beginning about 1.25 billion years ago) speaks of the early appearance of animals difficult enough to "nibble" on. The increase in the abundance and diversity of spines in acritarchs at the same time leads to the conclusion that even then there were predators large enough for such protection to be necessary. At the other end of the time scale relating to the Cambrian Explosion, one should note the absence of a number of the main types of the current fauna up to the end of the Cambrian, and typical Paleozoic ecosystems - up to the Ordovician.

Thus, today the point of view is refuted, according to which animals of the "modern" level of complexity (comparable to living invertebrates) arose within only a few million years of the Early Cambrian. However, the vast majority of modern phyla first appeared in the Cambrian (with the exception of molluscs, echinoderms, and arthropods, possibly emerging in the Ediacaran period). In addition, an explosive increase in taxonomic diversity was also observed at the beginning of the Cambrian.

"Explosion" of taxonomic diversity in the early Cambrian

"Taxonomic diversity" means the number of organisms that differ significantly in their structure. At the same time, "morphological diversity" means the total number of species and says nothing about the number of basic "designs" (many variations of a small number of basic types of anatomical structure are possible). There is no doubt that taxonomic diversity increased dramatically in the early Cambrian and remained at this level throughout the period - we can find modern-looking animals (such as crustaceans, echinoderms, and fish) at almost the same time, and often - and in common burials with organisms such as Anomalocaris and Halkieria, which are considered "uncles" or "great-uncles" of modern species.

Closer examination reveals another surprise - some modern-looking animals, such as early Cambrian crustaceans, trilobites and echinoderms, are in earlier deposits than some "uncles" or "great-uncles" of living groups that left no direct descendants. This may be the result of breaks and variations in the formation of fossil deposits, or it may mean that the ancestors modern organisms evolved at different times and possibly at different speeds.

Possible causes of the "explosion"

Despite the fact that rather complex three-layer animals existed before (and possibly long before) the Cambrian, evolutionary development in the early Cambrian seems to be extremely rapid. Many attempts have been made to explain the reasons for this "explosive" development.

Environmental changes

Increasing oxygen concentration

Earth's earliest atmosphere contained no free oxygen at all. The oxygen that modern animals breathe - both in the air and dissolved in water - is the product of billions of years of photosynthesis, mainly microorganisms (such as cyanobacteria). About 2.5 billion years ago, the concentration of oxygen in the atmosphere increased dramatically. Until that time, all the oxygen produced by microorganisms was completely spent on the oxidation of elements with a high affinity for oxygen, such as iron. Until they were completely bound on land and in the upper layers of the ocean, only local "oxygen oases" existed in the atmosphere.

Lack of oxygen could prevent the development of large complex organisms for a long time. The problem is that the amount of oxygen an animal can absorb from environment, is limited by the surface area (lungs and gills in the most complex animals; skin - in simpler ones). The amount of oxygen required for life is determined by the mass and volume of the organism, which, as the size increases, grow faster than the area. An increase in the concentration of oxygen in the air and in the water could weaken or completely eliminate this limitation.

It should be noted that a sufficient amount of oxygen for the existence of large vendobionts was already present in the Ediacaran period. However, a further increase in oxygen concentration (between the Ediacaran and Cambrian periods) could provide organisms with additional energy for the production of substances (such as collagen) necessary for the development of fundamentally more complex body structures, including those used for predation and protection against it.

Snowball Earth

There is abundant evidence that in the late Neoproterozoic (including the early Ediacaran period) the Earth was subjected to a global glaciation during which most of it was covered with ice, and the surface temperature was close to freezing even at the equator. Some researchers point out that this circumstance may be closely related to the Cambrian explosion, since the earliest known fossils date from a period shortly after the end of the last complete glaciation.

However, it is rather difficult to indicate a causal relationship of such catastrophes with the subsequent growth in the size and complexity of organisms. Maybe, low temperatures increased the concentration of oxygen in the ocean - its solubility in sea water almost doubles when the temperature drops from 30 ° C to 0 ° C.

Fluctuations in the isotopic composition of carbon

In sediments at the boundary of the Ediacaran and Cambrian periods, there is a very sharp decline, followed by unusually strong fluctuations in the ratio of carbon isotopes 13 C/ 12 C throughout the early Cambrian.

Many scientists have assumed that the original fall is due to the mass extinction just before the beginning of the Cambrian. . It can also be assumed that the extinction itself was a consequence of the previous decay of methane clathrates. It is widely known that the emission of methane and the subsequent saturation of the atmosphere with carbon dioxide causes a global greenhouse effect, accompanied by various environmental disasters. A similar picture (a sharp drop in the 13 C/ 12 C ratio with subsequent fluctuations) was observed in the Triassic, when life was recovering from the mass Permian extinction.

However, it is rather difficult to explain how a mass extinction could cause a sharp increase in taxonomic and morphological diversity. Although mass extinctions, such as the Permian and Cretaceous-Paleogene, led to a subsequent increase in the number certain types from insignificant to “dominant”, however, in both cases, ecological niches were replaced, albeit by other, but equally complex organisms. At the same time, no abrupt growth of taxonomic or morphological diversity was observed in the new ecosystem.

A number of researchers assumed that each short-term decrease in the proportion of 13 C/ 12 C in the Early Cambrian represents a release of methane, which, due to the small greenhouse effect and temperature increase caused by it, led to an increase in morphological diversity. But even this hypothesis does not explain the sharp increase in taxonomic diversity at the beginning of the Cambrian.

Explanations based on the development of organisms

A number of theories are based on the idea that relatively small changes in the way animals develop from embryos to adults can lead to dramatic changes in body shape.

Emergence of the system of bilateral development

The Hox genes in different groups of animals are so similar that, for example, you can transplant the human “eye-forming” gene into a Drosophila embryo, which will lead to the formation of an eye - but it will be a Drosophila eye, due to the activation of the corresponding “working” genes. This shows that the presence of a similar set of Hox genes does not at all mean anatomical similarity of organisms (since the same Hox genes can control the formation of such different structures as human and insect eyes). Therefore, the emergence of such a system could lead to a sharp increase in diversity - both morphological and taxonomic.

Since the same Hox genes control the differentiation of all known bilateral organisms, the evolutionary lines of the latter must have diverged before any specialized organs could form. Thus, the "last common ancestor" of all bilateral organisms must have been small, anatomically simple, and most likely susceptible to complete decomposition not preserved in fossils. This circumstance makes its discovery extremely unlikely. However, a number of venodobionts (for example, kimberella, spriggin or Arkarua), may have had a bilateral body structure (according to a number of scientists, this is not so - the symmetry of venodobionts is not bilateral, but sliding, which fundamentally distinguishes them from most other organisms). Thus, similar system development could have occurred at least several tens of millions of years before the Cambrian explosion. In this case, some additional reasons are needed to explain it.

The development of sexual reproduction

Organisms that do not use sexual reproduction change very little. In most sexually reproducing organisms, the offspring receive about 50% of their genes from each parent. This means that even a small increase in the complexity of the genome can give rise to many variations in the structure and shape of the body. Much biological complexity probably arises from the action of relatively simple rules on a large number of cells that function as cellular automata (an example of this effect is Conway's Game of Life, where complex shapes and complex behavior are exhibited by cells operating on extremely simple rules). The possible appearance of sexual reproduction or its significant development during the Cambrian explosion for very primitive and similar creatures may mean that there was the possibility of their interspecific and more distant interbreeding. This dramatically increased the variability. Only with the development of the genome do truly isolated species appear that do not interbreed with others. An example of modern creatures of this kind are corals.

development track

Some scientists suggest that as organisms become more complex, evolutionary changes general structure body superimposed secondary changes in the direction of better specialization of its existing parts. This reduces the likelihood of new classes of organisms passing through natural selection - due to competition with "improved" ancestors. As a result, as the general (at the level of the taxonomic class) structure is formed, a “development track” is formed, and the spatial structure of the body is “frozen”. Accordingly, the formation of new classes occurs "easier" in the early stages of the evolution of the main clades, and their further evolution takes place at lower taxonomic levels. Subsequently, the author of this idea pointed out that such a "freeze" is not the main explanation for the Cambrian explosion.

Fossils that could support this idea are ambiguous. It has been noted that variations in organisms of the same class are often greatest at the very first stages of clade development. For example, some Cambrian trilobites varied greatly in the number of thoracic segments, and subsequently this diversity has decreased significantly. However, samples of the Silurian trilobites were found to have the same high variability in structure as the Early Cambrian ones. The researchers suggested that the overall decline in diversity is due to ecological or functional limitations. For example, one would expect less variation in the number of segments after trilobites (resembling modern woodlice) developed a convex body structure, which is an effective way to protect it.

Environmental explanations

Such explanations focus on interactions between different kinds of organisms. Some of these hypotheses deal with changes in food chains; others consider an arms race between predators and prey that may have caused the evolution of rigid body parts in the early Cambrian; a number of other hypotheses focus on more general mechanisms of coevolution (the most famous example is the coevolution of flowering plants with insect pollinators).

"Arms race" between predators and prey

By definition, predation presupposes the death of the prey, which makes it the strongest factor and accelerator of natural selection. The pressure on the prey to better adapt must be greater than on the predators - because, unlike the prey, they have a chance to make a new attempt (this asymmetry is known as the "life against lunch" principle - the predator risks losing only lunch, while how the victim risks his life).

However, there is evidence (for example, fossils of spiny acritarchs, as well as holes made in the shell of claudinids) that predation was present long before the beginning of the Cambrian. Therefore, it is unlikely that it in itself caused the Cambrian explosion, although it had a strong influence on the anatomical forms of the organisms that arose during this.

Appearance of phytophages

Stanley (1973) suggested that the appearance of protozoa (single-celled eukaryotes) 700 million years ago, "nibbling" microbial mats, greatly expanded food chains and should have led to an increase in the diversity of organisms. However, today it is known that "gnawing" arose more than 1 billion years ago, and the extinction of stromatolites began about 1.25 billion years ago - long before the "explosion".

Growth in size and diversity of plankton

Geochemical observations clearly show that total weight plankton became comparable with the current already in the early Proterozoic. However, until the Cambrian, plankton did not make a significant contribution to the nutrition of deep-sea organisms, since their bodies were too small to quickly sink to the seabed. Microscopic plankton were eaten by other plankton or destroyed by chemical processes in the upper layers of the sea long before they penetrated into the deep layers, where they could become food for nekton and benthos (swimming organisms and inhabitants of the seabed, respectively).

In the composition of the early Cambrian fossils, mesozooplankton (medium-sized plankton, visible to the naked eye) was found, which could filter out microscopic plankton (mainly phytoplankton - planktonic "vegetation"). The new mesozooplankton may have been the source of the remains, as well as excreting excrement in the form of capsules large enough to submerge quickly - these may have been food for nekton and benthos, causing them to grow in size and diversity. If the organic particles reached the seabed, as a result of subsequent burial, they should have increased the concentration of oxygen in the water while reducing the concentration of free carbon. In other words, the appearance of mesozooplankton enriched the deep ocean with both food and oxygen, and thus made possible the emergence and evolution of larger and more diverse inhabitants of the deep sea.

Finally, the emergence of phytophages among mesozooplankton could form an additional ecological niche for larger mesozooplankton predators, whose bodies, plunging into the sea, led to its further enrichment with food and oxygen. Perhaps the first predators among mesozooplankton were larvae of benthic animals, whose further evolution was the result of a general increase in predation in the seas of the Ediacaran period.

Many empty niches

James W. Valentine made the following assumptions in several papers: abrupt changes in body structure are "embarrassing"; change is much more likely to exist if it encounters little (or no) competition for the ecological niche it targets. The latter is necessary for new type organisms had enough time to adapt to their new role.

This circumstance should lead to the fact that the implementation of major evolutionary changes is much more likely at the initial stages of ecosystem formation, due to the fact that subsequent diversification fills almost all ecological niches. In the future, although new types of organisms continue to emerge, the lack of empty niches prevents their spread in the ecosystem.

Valentine's model explains well the uniqueness of the Cambrian explosion - why it happened only once and why its duration was limited.

Notes

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Statistical analysis of traffic to our site convincingly indicates that greatest success popular science articles are used, and materials of this kind are viewed stably for a long time. So I decided to work in this direction again, covering a topic that has been worrying me for a long time.

The question of how the world could look like at the beginning of its journey has excited people's minds since time immemorial. For a long time, the mysteries of past eras remained secrets behind seven seals, and in the absence of scientific knowledge, mankind created myths, resembling a child surrounded by fairy-tale fantasies in a cradle. With the development of the scientific worldview, riddles have not disappeared anywhere, they have only acquired a concrete form. One of these mysteries is the Cambrian explosion.

It is known that the age of geological rocks can be determined stratigraphically: younger layers, as a rule, lie above the older ones. Based on the fossilized remains of extinct organisms that saturate the rocks, it is possible to recreate a picture gradual evolution life on earth. However, this gradualness suddenly breaks off at depths corresponding to the layers of the Cambrian period "541.0 ± 1.0 million years ago - 485.4 ± 1.9 million years ago). Almost all modern types of multicellular animals are found here, and then - as if a void, a mysterious Precambrian, as if an act of creation had taken place ... This phenomenon was called the Cambrian explosion in science.

Cambrian

However, in reality, the imprints of more ancient animals were discovered by scientists, but for a long time they were attributed to the Cambrian layers and identified with taxonomic groups of organisms that have survived to this day. Similar artifacts were encountered by German geologists in Namibia, South Africa in 1908, and by R. Sprig in the Ediacara of South Australia, in the early 1930s. XX century, who published in 1947 the work "Early Cambrian jellyfish of the Flinders Range of South Australia." To avoid the temptation to explain the unknown to the familiar - for this the researcher needs a certain courage. Only in 1952, Academician of the Academy of Sciences of the USSR B.S. Sokolov established the existence of the Vendian, a period preceding the Cambrian. “... for the first time, the so-called Ediacaran fauna of the skeletal Metazoa, originally considered Cambrian, took its true geochronological position ... The Vendian period (Vendian) is named after the oldest Slavic tribe of the Vendians (or Wends), who lived south of the Baltic Sea.”

Boris Sergeevich Sokolov

In this regard, I cannot help but tell about a curious case when, at the age of 5, I won a candidate of geological sciences in a dispute on this issue. Once again, guests gathered at our house, for some kind of family celebration. A completely different era in the life of the country was coming to an end, and now it seems like a dream of a prosperous Soviet Baku with tables full of fruits and sturgeon caviar, with regular visits to each other by a friendly horde of relatives. With my cousin, under the guidance of an older cousin, we played astronauts that evening, traveling blindfolded on window sills and cabinets, imagining them as other planets. And in my childhood I had a book on paleontology “The Living Past of the Earth”, with a geochronological table, which included the Vendian period ... Uncle, then a candidate of geological sciences, asked me: what period is the very first, and I answered that the Vendian. And the uncle answers: no, the Cambrian. I did not agree with him. After some time, rummaging through some literature, my uncle admitted that new scientific data had appeared, causing considerable amusement of my parents.

But back to the Cambrian explosion. With t.sp. stratigraphically, it is not so difficult to answer about the reasons for the observed explosive increase in the number of finds with the transition from the Precambrian to the Cambrian. In the Cambrian, skeletal organisms appear: shells, shells, spikes - all this is perfectly preserved in a fossilized form. Precambrian forms are soft-bodied and non-skeletal, a special set of circumstances is required for their imprints to leave a memory in the annals of our planet, and that is why nothing was known about them for a long time. Therefore, now the history of the organic world of the Earth is divided into 2 large eons: Phanerosa - the era of manifest life and Cryptosis - the era of hidden life. But what was the real reason for the so-called. "skeletal revolution?"

There are very diverse versions on this subject, those who are interested can always get acquainted with them on the Internet. For a long time, the domestic literature was dominated by the hypothesis that an increase in the concentration of Ca2+ ions in sea water due to geological reasons, which are necessary for building protective systems such as shells, shells, etc. - reason. However, even back in 2007, a different version came to my mind in the form of intuitive visual images, which seemed simpler and more logical (following the principle of Occam's razor that the shortest path to truth is in a straight line). Over time, it became clear that many scientists dealing with the problem followed the same path, and now this hypothesis is mentioned even in Russian school biology textbooks.

“...Thousands of specimens of representatives of the Vendian biota have already been studied, and none of them have been found to have damage or bite marks. This means that bioturbators, macroscopic carrion eaters, and predators that grind food were practically absent in the Vendian ecosystem. Dead organic matter was subjected only to microbial decomposition. By the way, in 2007 even these facts were not known to me.

So, predator-prey relationships among multicellular organisms appear only in the Cambrian (although there is evidence, and it is natural that they originated in the Ediacaran (an alternative name for the Vendian period). .), some animals began to consume others, provoking the Cambrian explosion through the escalation of the "arms race" of predators and prey ". Here we mean that the emergence of oxygen respiration made possible an increase in the rate of metabolism and energy, and here my scientific intuition is groping for some causal failure: the emergence of antagonistic ecological relations predator-prey is determined by progressive, in terms of efficiency of resource use, aromorphosis (aromorphosis - a progressive evolutionary leap) - the emergence of oxygen respiration. If we recall such a concept by V. I. Vernadsky as the pressure of life, due to its continuous striving cleverly harvesting biomass in the process of reproduction on the one hand and limited by available resources on the other, it is logical to assume that the predator-prey relationship arose as a result of those described by V.I. Vernadsky principles. In short, one day there were too many of them, and their weapons and what they used to protect themselves from each other turn well into stone ...

There is a hypothesis according to which Vendian animals could feed on microscopic symbiont algae living in their body, which in turn consumed solar energy in the process of photosynthesis, because many representatives of the Ediacaran biota seem to have been inhabitants of shallow waters flooded with sunlight. As an additional, this type of nutrition is also found in modern animals. In the Vendian period, this way of eating could also be the main one. The world of the Vendobionts, where no one ate anyone, McMenamin called the "Garden of Ediacara", with a clear allusion to the Garden of Eden. I had the same allusion.

What was the Vendian world like? The day was 3 hours shorter, and the year had 420 days. Other continents, other oceans… The Precambrian world is colorfully described by Ya.E. Malakhovskaya and A.Yu. Ivantsov ... "The bottom of the vast shallow seas and low-lying land areas were covered with carpets of bacterial mats, in some places forests of ribbon-like algae swayed." “It was a great glaciation: according to scientists, then in the sea ice swam even into the tropical zone, and the land was almost completely covered with glaciers. After the end of the Ice Age, the communities of microorganisms and algae returning to shallow waters already included multicellular animals. Among these soft-bodied creatures there were giants, reaching a length of one and a half meters, and very small ones, no more than 2-3 mm. Some swam or soared in the water column, others lived at the bottom: attached to it, lay freely or crawled. “Despite the century-long history of the study of Vendian prints, until recently there was no satisfactory answer to the question of who the Vendian organisms were - plants, animals, fungi, or belonged to another kingdom that has not survived to this day. Most researchers consider them to be multicellular animals, perhaps only because of the external resemblance of the prints to some invertebrates.

Charnia (Charnia masoni) led a sedentary lifestyle.

Tribrachidium (Tribrachidium heraldicum) sat motionless at the bottom, only the cilia on the outer surface moved slightly. Cilia caught small organic particles from the water and distilled them from the periphery to the center to the mouth, perhaps even to three mouths.

Dickinsonia (Dickinsonia lissa, Dickinsonia cf. tenuis, Dickinsonia costata) crawled. The largest, 1.5 m long, comes from Ediacara.

Kimberella (Kimberella quadrata) somewhat reminiscent of shellfish.

Yorgiya (Yorgia waggoneri), the ventral side of the body of which was covered with something similar to ciliated epithelium, sinking to the bottom, eating away a portion of the substrate under itself (the cilia of the epithelium captured and moved organic particles to the mouth). Then she swam to another place ... After the area of ​​the seabed on which the animals grazed was covered with sediment, their tracks could be preserved thanks to a dense organic film on which they were, as it were, “engraved”.

Ventogyrus (Ventogyrus chistyakovi) probably swam.

It makes no sense to list everyone in a popular science article ...

As a teenager, in post-Soviet Baku, I had the most beautiful dream of my life. My heels caressed the waters of the nighttime prehistoric sea. At the bottom among the rocks - sand and fluorescent lilac, green, turquoise sponges and bushes vaguely resembling coral polyps ... The burden of hundreds of millions of years of cruel evolution and the human history that followed - everything is far ahead and above ... There, on the shores of the Vendian Sea, I was seized lightness and serenity.

Then came the Cambrian trilobite. I touched his shell...

The Cambrian was advancing... I woke up.

Literature:

1. Malakhovskaya Ya. E., Ivantsov A. Yu. A colorful illustrated atlas of the most ancient soft-bodied animals of the Vendian period // Arkhangelsk, Publishing House of Pin RAS: 2003. 48 p.
2. Sokolov B. S. Essays on the formation of the Vendian // M .: KMK Ltd., 1997. 157 p.
3. Mario Aguilera. Dawn of Carnivores Explains Animal Boom in Distant Past // UC San Diego News Center, July 30, 2013.
4. Yastrebov S. A. The Cambrian Explosion // Chemistry and Life, 2016, No. 10.
5. Mark A. S. McMenamin. The Garden of Ediacara // PALAIOS, Vol. 1, no. 2 (Apr., 1986), pp. 178-182

In video format:

About the Cambrian:

All editions of "Evolution":

Darwin argued that the development of any species from its ancestor is a long and gradual process of change that passes through countless intermediate forms.

He realized that if his theory was correct, then there must have been thousands of these intermediate forms. Moreover, he was aware that the strength of his theory depended on the existence of these forms.

Thus, Darwin wrote that “between all living and extinct species there must have been an unthinkable number of intermediate and transitional connections. But without a doubt, if this theory is correct, such existed on our Earth.

But why, then, he wondered, expressing his own doubts, "we do not find them without counting in the deposits of the earth's crust?" He was painfully aware of the dearth of such fossils in geological strata, but he deceived himself and his readers: "The answer is chiefly that the data are not as complete as is commonly thought."

Nevertheless, this fact did not give him rest, and he even devoted a whole chapter to it in his book, arguing in it on the topic of "incompleteness of geological data."

Despite his strong reasoning, he clearly still felt somewhat uneasy about this situation, as soon as he found it necessary to state in print his belief that in "future ages ... numerous fossil connections will be discovered."

Excited about the theory and confident that by capturing more fossil-bearing strata they would successfully fill in this "incompleteness," geologists and paleontologists (scientists who study fossils) have made titanic efforts to fill in the gaps in the fossil record.

Surprisingly, given the huge resources that have been used to solve the problem over the years, these efforts have not yielded results. Professor Gould said that "the extreme rarity of transitional forms in fossil history continues to be guarded as the trade secret of paleontology."

In 1978, Gould's colleague Professor Niles Eldridge admitted in an interview that "no one has been able to find any 'intermediate' creatures: there are no 'missing connections' in the fossil record, and many scientists are now increasingly inclined to believe that these transitional forms never existed."

Professor Stephen Stanley writes: “In fact, in fossil history there is not a single convincingly confirmed case of the transition of one species into another. In addition, species have existed for astonishingly long periods of time.” No one, for example, has been able to find a fossil giraffe with a medium-sized neck.

If fossil history refuses to show the expected connections, what does it demonstrates? And what is she proves?

fossil history

Fossil history as we know it begins in what geologists call the Cambrian, which they estimate was about 590 million years ago. A few tiny fossils have been found in rocks from an earlier time: a few bacteria and some very unusual creatures, unlike anything found before or since, the Ediacaran fauna, which is about 565 million years old.

But they all seem to have died out shortly thereafter. It seems as if a few training exercises were scrawled in the book of life, then crossed out with a thick line: from that moment, real evolution began - or at least something began.

And this something had a dramatic character: as far as the animal kingdom is concerned, everything appeared at the same time. So sudden and mysterious was the emergence of a variety of life forms at that time that scientists, as we have seen, speak of the Cambrian explosion, which occurred, according to their data, about 530 million years ago.

The most astonishing discovery was that animals of all known forms, whether fossil or living, were then born. During this period, life chose its basic forms and did not change them anymore.

Moreover, although the entire Cambrian period is believed to have lasted about 85 million years, the actual appearance of all these new forms probably took place in about 10 million years or less.

In other words, the history of life on Earth reveals about 2 percent of creativity and 98 percent of subsequent development.

Simplified Animal Classification Scheme CURRENTLY LIVING ORGANISMS| Animal kingdom| PHILUM/Eumetazoa(true multicellular)| TYPE/Chordata (chordates)| SUBTYPE/Vertebrata (vertebrates)| CLASS/Mammalia (mammals)| ORDER/Carnivora (carnivores)| FAMILY/Felidae (felines)| ROD/Felis (cats)| SPECIES/catus > Felis catus (domestic cat)

It was according to their structure that all living beings were first classified. A complex system has been developed that divides all forms of life into two vast kingdoms - the animal kingdom and the vegetable kingdom. They, in turn, are subdivided first into phylums (from the Greek word for "tribe"), and then into ever smaller units, down to species and subspecies.

The animal kingdom is usually divided into thirty-seven phyla. All these phyla arose during the Cambrian period. Since then, evolution has proceeded only along the line of modification of the basic plan. In addition, there is no evidence of any previous development of them. There is no evidence that they "evolved" in the Darwinian sense of the term. They all appeared in fossil history ready-made - fully formed creatures with their own very distinct features.

Scientists are perplexed. Calling our attention to the fact that “every evolutionary change since the Cambrian has been just variations on the same basic themes,” Professor Jeffrey Levintop of New York University asks, “Why are ancient forms so stable?” He doesn't have an answer.

What is very clear from the geological record is that this stability is the norm. Fossil forms of animals or plants appear, exist and develop for millions of years, and then disappear - but their structure changes little.

If any changes are observed, then they are of a gradual nature and are limited mainly by size: the whole animal or plant increases - or its individual signs. It is not observed that one form changes into another, even a relatively close one: the mouse never evolved into a rat; the sparrow never became a thrush.

In addition, such changes are, apparently, very selective. A huge number of creatures living on Earth to this day have not undergone any significant changes in their structure over the entire long period of their existence. This goes against all of Darwin's expectations.

Oysters and bivalves now have shells: they first appeared about 400 million years ago. Coelacanth and lungfish have lived on Earth without any significant changes for about 300 million years. Sharks have maintained their current appearance for 150 million years. Sturgeon, caiman tortoise, alligators and tapirs - all these species have shown an enviable stability of form for over 100 million years.

Modern opossums differ from those that lived 65 million years ago only in very minor ways. The first tortoise had the same shell as today; the first snakes are almost no different from modern snakes; bats also remained virtually unchanged, as did frogs and salamanders.

What, then, has evolution stopped? Or is there some other mechanism or factor at work?

An example often used to demonstrate evolution is the horse. It is assumed that it began with a small four-toed hyracotherium that lived 55 million years ago and developed into modern Equus, living for about 3 million years. Everywhere you can see elegant and convincing diagrams and museum displays depicting the progressive evolution of the horse. They skillfully demonstrate how the fingers gradually converged to one, how the size of the animal increased markedly, and how the teeth changed with a change in diet.

However, experts now generally accept that this line of the slow but sure transformation of a dog-sized animal into today's large horse is "largely apocryphal." The problem is - and this is a common problem in reconstructing evolution from fossil data - there are many gaps between the various fossil horse species that are included in this series.

Starting from the first kind hyracotheria, whose own ancestor remains a mystery, no connection to the alleged "second" horse is known, and so on.

What we have is not a line of development, it is not even a family tree leading to the modern Equus, but it is a huge shrub, in which only the tips of numerous branches are visible, and any question as to the existence of its trunk is left open.

In any given period of time, there have been several different types of horse - some with four fingers, others with fewer, some with large teeth, others with small ones. Horses also first increased in size, then decreased, and then increased again. And as a constant source of irritation - the absence of uniting species.

Finally, we must also recognize that the supposed ancestral horse is not all that different from the modern horse. Aside from a few minor changes to the feet and teeth and an increase in size, not much has changed significantly.

This very small difference, presented as proof of evolution, even if true, is hardly impressive in the 52 million years it took. To put it bluntly, to regard this pseudo-sequence as proof of evolution is more an act of faith than a scientific fact.

Sudden origin of species

Fossil history is characterized by two things. The first, as we have already seen, is the stability of plant or animal forms once they have already appeared. The second is the suddenness with which these forms appear and, in fact, subsequently disappear.

Accuracy of fossil history

Total number of living terrestrial vertebrates 43

Total number recorded in fossil history 42

Thus, the percentage of discovered fossils is 97.7%

Total number of living families of terrestrial vertebrates 329

Total number recorded in fossil history 261

Thus, the percentage of discovered fossils is 79.3%

We can conclude that fossil history provides an accurate statistical picture of the forms of life that have existed on Earth. Therefore, appealing to the incompleteness of the fossil record as a way of explaining the gaps is not very convincing.

New forms arise in fossil history without obvious ancestors; just as suddenly, they disappear without leaving any obvious descendants. It can be said that practically fossil evidence is the history of a huge chain of creations, united only by the choice of form, and not by evolutionary connections.

Professor Gould sums up the situation thus: “In any particular region, a species does not arise gradually by the planned transformation of its ancestors; it appears suddenly and immediately and "fully formed".

We can observe this process almost everywhere. When, say, about 450 million years ago, the first fossil land plants appeared, they arose without any signs of a previous development. And yet even in that early era all major varieties are present.

According to the theory of evolution, this cannot be - unless we allow that none from the expected binding forms was not fossilized, i.e. did not turn into a fossil. Which seems highly unlikely.

It is the same with flowering plants: although the period preceding their appearance is characterized by a large variety of fossils, no forms have been found that could be their ancestors. Their origin also remains unclear.

The same anomaly is found in the animal kingdom. Fish with spines and brains first appeared about 450 million years ago. Their direct ancestors are unknown. And an additional blow to evolutionary theory is that these first jawless but shelled fish had a partially bony skeleton.

The commonly presented picture of the evolution of a cartilaginous skeleton (as in sharks and rays) into a bony skeleton is, frankly, incorrect. In fact, these boneless fish appear in fossil history 75 million years later.

In addition, an essential stage in the supposed evolution of fish was the development of jaws. However, the first jawed fish in fossil history appeared suddenly, and it is impossible to point to any earlier jawless fish as the source of its future evolution.

Another oddity: lampreys - jawless fish - exist perfectly to this day. If jaws offered such an evolutionary advantage, then why didn't these fish become extinct? No less mysterious is the development of amphibians - aquatic animals capable of breathing air and living on land. As Dr. Robert Wesson explains in his book Beyond Natural Selection:

“The stages at which fish gave life to amphibians are unknown… the very first land animals appear with four well-developed limbs, shoulder and pelvic girdle, ribs and a distinct head… A few million years later, over 320 million years ago, suddenly appears in fossil history a dozen orders of amphibians, none of which seems to be the ancestor of any other."

Mammals show the same suddenness and rapidity of development. The earliest mammals were small, secretive animals during the age of the dinosaurs, 100 or more million years ago. Then, after the mysterious and still unexplained extinction of the latter (about 65 million years ago), more than a dozen groups of mammals appear in fossil history at the same time - about 55 million years ago.

Among the fossils of this period are fossilized specimens of bears, lions and bats, which have a modern look. And what further complicates the picture is that they do not appear in one particular area, but simultaneously in Asia, South America and South Africa. On top of all this, it is not certain that the small mammals of the dinosaur era were indeed the ancestors of later mammals.

All fossil history is littered with gaps and mysteries. For example, no fossil links are known between the first vertebrates and primitive creatures of an earlier period - chordates - which are considered the ancestors of vertebrates.

The amphibians that exist today are strikingly different from the first known amphibians: there is a gap of 100 million years between these ancient and later forms in fossil history. It seems that Darwin's theory of evolution is crumbling to dust before our very eyes. It is possible that somehow the Darwinian idea of ​​"natural selection" can be salvaged, but only in a substantially modified form.

It is clear that there is no evidence of the development of any new forms of plants or animals. Only when the living form has appeared, only then, perhaps, does natural selection play its role. But it only works on what already exists.

Not only scientists, but also students of colleges and universities conduct breeding experiments on the fruit fly - Drosophila. They are told that they are showing clear evidence of evolution. They mutate the species, giving her eyes of different colors, a leg growing out of her head, or perhaps a double thorax.

Perhaps they even manage to grow a fly with four wings instead of the usual two. However, these changes are only a modification of the already existing species features of the fly: four wings, for example, are no more than a doubling of the original two. Never been able to create any new internal organ how it was not possible to turn a fruit fly into something resembling a bee or a butterfly. You can't even turn it into another kind of fly.

As always, she remains a representative of the genus Drosophila."Natural selection may explain the origin of adaptive change, but it cannot explain the origin of species." And even this limited application runs into problems.

How, for example, can natural selection explain the fact that humans, the only species of living beings, have different blood types? How is he able to explain that one of the earliest fossil species known to science, the Cambrian trilobite, has an eye so complex and so effective that it has not been surpassed by any later member of his phylum? And how could feathers have evolved? Dr. Barbara Stahl, author of an academic work on evolution, admits: "How they arose, presumably from reptile scales, is beyond analysis."

From the very beginning, Darwin knew that he was facing deep problems. The development of complex organs, for example, undermined his theory to the limit. For until such an organ began to function, why should natural selection encourage its development? As Professor Gould asks, “What is the use of imperfect rudimentary stages, advantageous structures? What is the use of half a jaw or half a wing?” Or perhaps half an eye? The same question arose somewhere in Darwin's mind. In 1860, he confessed to a colleague: "The eye to this day gives me a cold shiver." And no wonder.

Proposed evolution of vertebrates. This diagram shows the variety of vertebrate groups that have spread since the time. The dotted lines represent the missing links that are required - in order to link these groups together - evolutionary theory. These links have not been found in fossil history.

A final example - evidence, if you like - that natural selection (if it is indeed a real mechanism of change) requires more understanding is the fact concerning the physiological functions of the sloth, which is given by Dr. Wesson:

“Instead of urinating immediately, like other tree-dwellers, the sloth saves its faeces for a week or more, which is not easy for an animal that eats a rough plant diet. After which he descends to the ground, which he otherwise does not step on, defecates and buries the excrement.

This dangerous behavior is supposed to have the evolutionary advantage of fertilizing the treehouse. That is, a series of random mutations led to the fact that the sloth developed a habit unlike him in the administration of physiological needs and that this improved the quality of the foliage of the tree he had chosen so much that it caused him to have more numerous descendants than sloths who defecate directly on trees…”

Does evolution have other forms or modes of "natural selection" that we don't even know about yet, or is it necessary to use something completely different to explain the sudden spread in fossil history - perhaps a cosmic sense of humor?

Wrong evolution

Problems with fossil data have been known from the beginning. For a century or so, scientists simply hoped that the problems were temporary, that discoveries would be made that would fill in the gaps. Or perhaps some evidence will be found that these gaps are not due to problems with evolution, but to the irregularity of the geological process.

Eventually, however, patience began to run out. The consensus in the scientific world was broken in 1972 when Stephen Jay Gould and Niles Eldridge presented a revolutionary joint paper at a conference on evolution. Their report directly refuted Darwin's theory.

They argued that while the fossil record is certainly far from satisfactory, the observed sudden appearances of new species are not evidence of incompleteness in the fossil record, but rather reflect reality. The origin of species may not have been gradual evolutionary process, but a process in which long periods of stability were occasionally punctuated by sudden massive changes in living forms. With this argument, Gould and Eldridge could explain the absence of "missing links": they argued that they simply did not exist.

As well as explaining perhaps fossil history, this idea is still based on the notion that the development of life is random, random. However, it can be shown that evolution, however it may have taken place, is unlikely to have been random process.

The development programs for plant and animal forms are contained in the genetic code. This code is very complex, and the number of variations that could be involved is huge. Could this code have evolved randomly? A simple acquaintance with the numbers shows that this could not be. If, for example, a monkey were sitting at a typewriter, knocking at random on the keys every second, how long would it take for the monkey to - by chance - come up with a meaningful word of twelve letters? For this, it would take almost 17 million years.

How long would it take for the same monkey to - by chance - get a meaningful sentence of 100 letters - a chain of characters much less complicated than the genetic code? The probability of this is so low that the odds against it exceed the total number of atoms in the entire universe. In fact, we should talk about the impossibility of randomly generating a meaningful sequence of 100 characters. It remains to be concluded that it is just as impossible that the complex genetic code of life could have happened by chance, as required by the theory of evolution.

Astronomer Fred Hoyle, with characteristic accuracy, wrote that the probability of accidentally creating higher forms of life is similar to the probability that "a tornado sweeping through a junkyard could collect a Boeing 747."

And in this case, if the genetic code is not created by a random process, then it must be assumed that it was created by a non-random process. Where might this thought lead us?

Guided evolution

In 1991, Wesson's book "Beyond Natural Selection" became a new and powerful challenge to mainstream science. He dismissed attachment to Darwinian evolution as "an indulgence of the ancient dream of the universe, likened to a huge clockwork." Wesson points out that no animal can be considered in isolation.

He invites us to take a broader view: “Organisms evolve as part of a community, that is, as an ecosystem ... which inevitably evolves together. Rather, we need to talk not about the origin of species, but about the development of ecosystems ... "

In a truly radical revision, Wesson proposes to apply the findings of chaos theory to evolution in order to make sense of all the amazing and strange phenomena that we observe both in fossil data and in living organisms.

5. Fossils

6. Equus, or real horse.

From M. Baigent's book "Forbidden Archeology".