Which kind is evolutionarily the most successful

The living

The theory of evolution says that the whole diversity of life has emerged from an original living being through gradual changes and species formation. Much evidence from a wide variety of areas shows that evolution is a fact, and that the process of natural selection discovered by Charles Darwin is its most important driving force.

Wheel turning peacock: Peacock cocks have to be beautiful, otherwise they have no chance with the hens - “sexual selection” (>> here) also contributes to evolution. Photo: “BS Thurner Hof”, from >> wikipedia, license: >> cc 3.0.

The theory of evolution goes on the groundbreaking discoveries Charles Darwins (>> here) back and was through Theodosius Dobzhansky, Ernst Mayr and others further developed through the incorporation of the knowledge of modern genetics obtained after Darwin into today's “synthetic theory of evolution”: Mutations (and other mechanisms such as the mixing of the genetic material during sexual reproduction, “genetic drift” and migration, >> more) create differences in the characteristics of living beings (“variability of the phenotype”, >> here) to which the natural selection works. Genetic changes that increase the ability of their carriers to reproduce will prevail in the long run; and since the ability to reproduce depends on a better adaptation to the environment, this kind of selection will lead to an ever better adaptation of species to the environment. If, for example, the environment cools down, animals with thick coats will live longer - and thus have greater chances of reproducing, which in the course of time the coats of this species will become more and more dense - until further densification no longer offers any advantages. Natural selection thus has an effect on the gene pool (the entirety of the genes in a population): genes that lead to the development of favored traits become more frequent; Genes that cause unfavorable traits are less likely to end up disappearing altogether. The species living today did not always exist; they emerged from predecessor species. The predecessors of humans, for example, were species that were ape-like (but not today's apes, which have also evolved; >> more).

These changes take place graduallyA bird did not suddenly hatch from a reptile egg, but the birds have evolved from reptiles through numerous developmental steps. (The speed of these changes differs from species to species: changes in the environment can accelerate evolution, in a stable environment a species can appear to remain unchanged for a very long time, like the so-called “living fossils”). The diversity of life arose from the fact that it was Speciation can happen: The genetic exchange between the descendants of a species is prevented (be it that they become genetically incompatible, be it that they colonize different habitats), so that from now on they go different ways. This resulted in two species, and the frequent repetition of this process led to today's biodiversity. So all of today's species are one common ancestors back, and this explains why all living beings today have a common genetic code and uniform biochemical processes of energy production - they are those of that common ancestor.

In the meantime, the evidence for evolution is so numerous that it is considered a fact among natural scientists (see also >> here)). Findings from the most varied areas of biology speak in favor of evolution.

Evidence for evolution

Fossil finds (>> more) are perhaps the most important evidence for evolution: In the oldest rocks there are simple forms of life, in younger rocks they are gradually becoming more and more complex. The most recent fossils are most similar to today's life forms. The development of life can be traced from the data of the fossils (overview >> here, description >> here); Fossils can be used to trace evolutionary changes in a species and the emergence of new species. This is particularly impressive with microscopic plankton from the sea: Due to the large number of individuals and the deposition of dead individuals in the sea sediment, the development can often be followed over millions of years. But even with larger living beings, lineages of descent could be shown remarkably completely in fossil series in some cases, for example those from fish to amphibians (>> more), from reptiles to mammals (>> more), from ungulates to the Whales or the history of the horse. Another example is the human evolutionary history (>> more). One of the most important findings from fossil finds is that new structures are usually derived from existing structures, for example the legs of mammals are no different from transformed fish fins or the wings of birds are created from the forelegs of dinosaurs.

Evolution thus provides an explanation for something that biologists previously called Homology - Corresponding structures in different organisms: the wings of birds and the front legs of mammals are similar, as both emerged from the front legs of dinosaurs, and these from the bones of the fish's fins. The development of new structures on the basis of the existing ones is also the only meaningful explanation for a number of other phenomena: the appearance of rudiments, structures that have lost their original function in the course of evolution, or of atavisms, the occasional appearance of features or properties that have actually long since been lost in the course of evolution. Well-known examples of Rudiments are the human tailbone, a remnant of the mammalian tail, or the appendix, the remainder of an intestinal appendage. Existing structures are degenerating because maintaining them costs energy unnecessarily if their function ceases to exist - for example, birds on islands where no predators live and where food is easy to find often lose the functionality of their wings. Sometimes such structures also get new functions, so the wings of the penguins became fins, with the help of which they became excellent swimmers. AtavismsFor example, the occasional outgrowth of the coccyx into a real tail or the formation of several toes in horses (the hoof originated from an originally fifteen ancestor), showed the biologists that the genes for characteristics that have become superfluous are not removed from the genetic make-up, but just switched off; Atavisms arise when they are reactivated for whatever reason. Modern genetic studies have confirmed that about the human being several thousand switched off genes owns. Like all primates, for example, we have a switched off gene for the production of an enzyme with which we could produce vitamin C: Apparently a common ancestor of all primates lost this ability and was not punished for this due to his vitamin C-rich diet - even switched off Genes would be difficult to explain without evolution.

Evolution also explains an ancient mystery that puzzled biologists before Darwin: That Appearance and subsequent disappearance of structures in embryonic development. The embryos of mammals develop gill arches and a fish-like tail, which later disappear again; Human embryos are densely hairy from the sixth month to about a month before birth. In the meantime, numerous developments have been traced in detail - a textbook example is the origin of the ossicles hammer and anvil from the 1st gill arch and the stapes from the 2nd gill arch of fish (via a “detour” from hammer and anvil as bones in the lower jaw of reptiles and the stapes as bones in the upper jaw of fish and amphibians). The structural development in the embryo rudiments of this evolutionary history. Obviously, part of the genetic "development program" of our ancestors is still active within us; some of the structures that have been transformed in evolutionary history must presumably first develop in the individual before they can be transformed. Embryonic development and the great Similarity in embryos of related animal groups (see >> here) are meaningful to explain if you know about the derivation of new structures from old structures in evolutionary history, and therefore also evidence of evolution.

The emergence of new structures from old ones also limits the possibilities of evolution and leads to numerous Compromise (and is a contradiction to the assumption of an “intelligent design”): An S-shaped spine with intervertebral discs or our knee joint, for example, can be explained if one knows that a four-legged vertebrate has stood up here; However, frequent herniated discs and frequent damage to the medial meniscus, medial ligament or anterior cruciate ligament in the knee show that they are not “perfect”. Evolution can also cause problems such as hiccups (a result of the gill breathing of tadpoles), swallowing (a result of the oral cavity, which is used for speaking, swallowing and breathing at the same time) and sleep apnea (also a result of language: the flexible throat can during sleep block the airways), but with an “intelligent designer” one would have to speak of construction flaws.

Charles Darwin was one of them geographical distribution of plants and animals was substantially stimulated to his theory; in combination with the knowledge gained since then, especially on >> plate tectonics, evolution is the best explanation for biogeographical questions. It explains both the differences - why are both flora (eucalyptus forests ...) and fauna (marsupials ...) in Australia so different from the rest of the world? Because Australia was the first to separate itself from the rest of the continents - as well as the similarities - why is the wildlife of North America and Europe more similar than that of South America and Africa? Because the latter have been separated from each other for 80 million years, but the former were connected by a wide land bridge 40 million years ago. It is also interesting to ask how it is that different species can develop very similarly, so that the cacti from North and South America, for example, can hardly be distinguished from the very similar milkweed plants from the ancient world or many marsupials in Australia resemble mammals elsewhere? Evolution provides an answer: the species were subjected to very similar natural selection, which ultimately led to very similar results. Biologists call this "convergent evolution”. (But why would a creator bother creating two different but very similar species with very similar ecological preferences?). The fauna and flora of oceanic islands provide further evidence of evolution: on many such remote islands, such as Hawaii, Galapagos or Tahiti, there are numerous, often endemic, plants, birds and insects, but no freshwater fish. Amphibians, reptiles or mammals. This cannot be due to unsuitable habitats, as the successful settlement of all these groups by humans shows. The difference: plant seeds, birds and insects spread through the air; Freshwater fish, amphibians, reptiles, or mammals do not. They simply never reached these islands (before humans brought them there). (But why should a creator have refrained from equipping Tahiti with freshwater fish?) A similarly interesting development can be found on islands that have been separated from the mainland for a very long time: For example, a unique flora and fauna developed on Madagascar includes about 37 species of lemurs, a group of animals that does not occur elsewhere (biologists call such a splitting of an original species into numerous new species “adaptive radiation” (for example: fanning out as a result of adaptations). Otherwise, the flora and fauna are similar of islands always the strongest those of the neighboring continents. Why? Because they were settled from these islands and then developed there. An example are the famous Darwin's finches; Darwin's only suspected relationship of the By the way, finches on the Galapagos Islands have now been detected using molecular biological techniques - as well as their ancestry from the coconut finch that is common on the Coconut Island.

It is lately anyway molecular genetic evidencethat underpin evolution further: Molecules, such as proteins or the DNA of genes (>> more)), like body structures, undergo evolution. The more closely related two living things are, the more similar are their molecules (and of course the universal occurrence of DNA in all living things is the best evidence of Darwin's idea of ​​common ancestry). Molecular genetic investigations were able to confirm many palaeontological and morphological-anatomical findings, and also provide answers where the classical methods did not provide unambiguous findings. Just as important: many molecules change at a fairly constant speed and can thus - as calibrated against well-dated fossils - serve as molecular clocks with which evolutionary events can be dated. For example, it has been shown that chimpanzees and humans evolved from a common ancestor five to eight million years ago (>> Man).

The natural selection

The idea of ​​evolution existed before Darwin, his truly new idea was that of natural selection (also “natural selection”) - an unconscious process through which external factors of the environment affect the reproductive success of individuals of a species and change them in such a way that they adapt better and better to the environment over time. This process replaced the Creator in evolution, who was previously the only conceivable cause of the adaptation to the environment observed in nature; and it is still misunderstood by many laypeople to this day.How can such a selection lead to animals that resemble plants (such as grasshoppers that resemble a leaf) or plants that resemble animals (such as orchids, whose flowers look like insects)?

There are three prerequisites for natural selection: The individuals of a species must differ from one another distinguishwho have differences inheritable and the genetic differences must relate to the Reproductive success impact. Darwin believed in natural selection through the impressive successes of artificial selection in animal breeding, and today it can be directly demonstrated: Bright beach mice live on the Gulf coast of Florida. The experiment shows that this is an adaptation: on the sandy soil, dark mice are more often eaten by birds of prey than light mice. This has an effect on reproductive success, since many dark mice are eaten before sexual maturity; and the difference is hereditary, it goes back to the exchange of a single base pair in the mouse DNA - the beach mice are therefore a result of natural selection (see also >> here). Natural selection is also not a random process: only the underlying genetic mutations - such as the one that led to the exchange of the base pair in the beach mice - are random; the differences caused by this are then “read out” according to their adaptation value: Individuals who are better adapted to their environment have advantages.

The easiest way to detect natural selection is where generations occur quickly one after the other, for example in the case of bacteria: The American bacteriologist Richard Lenski and his colleagues have been studying the intestinal bacterium Escherichia coli since 1988; due to the rapid succession of generations (six to seven per day), they are now reached 45,000 generations and were able to demonstrate, among other things, the emergence of completely new metabolic pathways (the publications on the results can be found at http://myxo.css.msu.edu/cgi-bin/lenski/prefman.pl?group=aad). The evolution of bacteria is not only rapid in the laboratory, but also in nature: it is one reason for the rapid adaptation of bacteria to antibiotics or penicillin, which threatens to dull these miracle weapons of medicine a good 60 years after their introduction.

In the case of larger animal species, natural selection is naturally more difficult to show due to the long generations: The American evolutionary biologist John Endler was also able to show in guppies that males become better and better camouflaged in the presence of predatory fish, which are dangerous for them, but always in their absence become more colorful (which attracts the females). And scientists were able to show that the beak size of the middle-ground finch (Geospiza fortis), one of the Darwin's finches, changes between dry and wet years; the adaptation to the environment thus has measurable effects. (What is particularly exciting for biologists, however, is that the same gene can have similar but different effects in different animal species: a gene called BMP4 causes the beak of the Great Ground Finch (Geospiza magnirostris, also a Darwin's finch) to grow to its large size , with which the finch can open large seeds and nuts. The same gene has the effect of developing strong jaws in cichlids in Lake Victoria, with which these mussel shells open. In the same way, the development of fish fins, bird wings and human arms is controlled and played by the same gene The human “language gene” FOXP2 also plays a crucial role in finch song. Such genes, which are found throughout the animal world, prove Darwin's theory of common ancestry.) The changes Although guppies and Darwin's finches are small - in evolutionary history, millions of times more time was available - they prove that natural selection is actually effective.

In the course of time, very complex structures, such as the proverbial eagle eye, can arise (see also >> here)). Here, too, Darwin had already recognized and showed that less complex eyes showed a possible path of origin: It runs over light-sensitive skin segments (as found in flatworms), over indentations in this skin segment (protects the light-sensitive skin segments and makes it easier to determine the direction of incidence of light, found in some snails) and lens formation (concentration of light, in marine snails) towards the eye of mammals. Each of these intermediate stages had an adaptive advantage for itself (one of the most important consequences of evolution, which knows no “end goal” for which sacrifices would have to be accepted in between.). The evolution of other complex structures has yet to be explained, but our ignorance is not an argument that it could not have existed, as advocates of “intelligent design” believe: for natural scientists, this claim is an invitation to “keep your hands on your lap when it is obvious that there is still a lot to be done ”(Nathalie Angier) and an impoverishment of what really happened, which in a comprehensible way leads to the most fantastic results. They are "simply a sign of intellectual laziness" (Richard Dawkins' aptly phrase).

"Intelligent Design"

The main message of evolution - that the diversity of living beings on earth arose as a result of natural processes - was not only met with skepticism in Darwin's time; religious fundamentalists still demand that the biblical version of divine creation be taught in schools instead of evolution. The majority of Christians can live with evolution; they have learned since the Enlightenment that the Holy Scriptures are not a factual report, but are to be understood in a figurative sense. Many natural scientists are also believers: They believe that God created the world - and that he reveals himself in the laws of nature. While the laws of nature can be researched with scientific methods, the question of God is a matter of faith; Belief and knowledge do not have to be mutually exclusive.

But one can construct a contradiction: In some US states it was forbidden for decades to teach in schools a “theory that contradicts the biblical story of the divine creation of man” (as the Tennessee wording), and that is why many believe today Americans, God created man as he is. In the meantime, these bans have been abolished, but Bible fundamentalists are now contrasting the theory of evolution with an allegedly scientific theory of “intelligent design” and demanding that it be taught in schools. This “theory” cannot exist scientifically, it mainly consists of omissions and misinterpretations - see for example the technical analysis in the statement of biology professor Kevin Padian on the occasion of the case “Kitzmiller vs. Dover School Area District” >> here (in English), one of the many legal disputes in the USA on the subject [a comprehensive overview of these can be found on a (English) website of the >> National Center for Science Education].

The question of a divine Creator is of course not already refuted by supporters who argue incorrectly in the natural sciences; but the belief in the creation of species by a perfect Creator raises some questions that Darwin asked: Why does a whale have stunted hand bones? Assuming that whales have gone from land into the water, the hand bones can be understood as remnants of their previous life, but why should God put hand bones on a whale? (In this sense, many more questions would occur to humans: about the structure of the spine, knee (>> here) and inguinal canal, for example, which can be explained if one looks at the evolutionary history, but hardly speaks for a perfect creator; likewise little like hiccups (a late consequence of the gill breathing of tadpoles), ingestion (a consequence of the oral cavity, which is used for speaking, swallowing and breathing at the same time) and sleep apnea (also a consequence of language: the flexible throat can block the airways during sleep) Darwin also wondered why the Creator did not plant such well-adapted animals as camels in all deserts, and why mouse-like animals in Australia are more related to the kangaroos than to the mice elsewhere, and Darwin's theory could provide answers, therefore she has prevailed. That styles change is a fact; literal interpretation of the Bible contradicts our knowledge.

Presumably, however, it is not the factual justification of an “intelligent design” that is decisive for its followers, but a moral discomfort: If we were not created by a divine creator, but are a product of “selfish” evolution, what justification is there for moral behavior? If we are animals, why shouldn't we behave like animals? Book titles such as “The Selfish Gen” contribute to this discomfort - although most of those who cite this book as evidence have hardly read it. The author, Richard Dawkins, only shows in the book that genes that lead to better adaptations prevail at the expense of less beneficial genes, that is, behave as if they were selfish. Selfish genes can also lead to unselfish behavior, if this is the better adaptation. And in fact what has led to the special role of humans is our ability to cooperate (>> here). In any case, the majority of human behavior is not evolutionary but cultural, and both immoral and moral behavior can have a religious as well as a secular basis. But in Roman times it was still considered pleasant entertainment to watch how fellow men were torn to pieces by wild animals; today this would be considered barbaric anywhere in the world. So we can change, and the recognition of evolution does not mean that we are helplessly at the mercy of some (already wrongly feared) genetic law of the jungle.

As Darwin correctly recognized, the direction of natural selection is determined by the environment of a living being. The decisive factors can be caused by the inanimate environment (such as climatic factors) or by other living beings - in short: the entire ecosystem (>> more) influences natural selection. However, since ecosystems differ from one another, different factors affect the organisms of different ecosystems, which lead to geographical variability - an important factor for the emergence of new species.

Sexual selection

Potential sexual partners are among the most important environmental factors that affect reproductive success. They are so important that they sometimes produce results that seem absurd at first glance. A classic example that already preoccupied Charles Darwin is the magnificent train of the peacock cocks. There is hardly anything more beautiful in nature than a peacock turning a wheel during courtship (>> photo); but the train hinders the peacock considerably when flying. Why do they still exist? The answer is sexual selection: in experiments it has been shown that peacock cocks prefer cocks that turn the biggest wheel during courtship and thus increase their chances of reproduction. The same applies to many other animal species in which the males have conspicuous characteristics: these are always preferred by the females or increase the chance of reproduction in some other way (e.g. the large deer antlers, with which this rival out of the field beats).

Such striking differences between the sexes are what biologists call “sexual dimorphism”, and the males are almost always more beautiful or larger. Biologists explain this in terms of the different reproductive strategies: while females with a limited number of eggs and considerable work in rearing their offspring have to be selective about their mate, the males have so many sperm and often disappear again after fertilization, so that can easily fertilize as many females as possible and not have to waste any effort on the selection. If, on the other hand, females and males raise their offspring together, there are often no noticeable differences between males and females. (And if they do, this is because the partners often “cheat”, as genetic studies have shown.) In individual cases, the females are also more beautiful, for example with the seahorses: Here the male partners raise the young; are those who invest more in rearing and should therefore choose their partners carefully - the exception confirms the theory.

But why do (mostly) females choose their partners for beauty? Does this behavior have any adjustment value? Yes, many evolutionary biologists believe. If, for example, a peacock has a particularly splendid train and still reaches sexually mature age, it must have particularly good genes - the hen recognizes the “genetic quality” of its future partner via the detour via the train. Hens that preferred roosters that turn beautiful wheels were rewarded in evolution because these roosters also had better genes. Using the example of the gray tree frog living in the east of the USA, biologists were able to show that the males that call longer (and are preferred by the females) actually have better genes - they survived significantly better than tadpoles and produced more offspring. And young peacocks of fathers with long trains also survive better. In other cases, however, such evidence has not been found, and sometimes sexual selection may simply be a result of entirely different advantages: For example, if an animal species likes red - which can develop because ripe berries are often red - females may also prefer red-colored ones Male. In Australian grass finches, an artificially attached white cockscomb also increased the reproductive success of the males - so it cannot be a hidden sign of better genes that made the females do this, but a preference for another reason.

Some researchers suspect that sexual selection also played a role in human development: the upright gait could have resulted from the fact that our female ancestors preferred males who were particularly good at walking upright; and the growth in size of the brain was also accelerated by the fact that the capabilities of the brain had impressed the females. The preferred characteristics would have resulted in greater reproductive success of their carriers, and so ultimately prevailed. There are also a number of theories that see adaptation to the environment as the driving force for upright walking and brain growth (>> more); How big which influence actually was is still being discussed intensively.

The emergence of new species

The question of how new species arise could not really be answered by Darwin with the knowledge of his time. Since the species is defined as the group whose individuals can have fertile offspring with one another, the members of a species represent a reproductive community. New traits that have arisen, for example, through a mutation, can spread within a species. In this respect, the species is also the unit of evolution. New species emerge when the reproductive community is divided, that is, when something effectively prevents reproduction from one part of the group to another. A first indication of possible mechanisms was provided by similar species that were spatially separated. If the occurrences of a species are spatially separated (such as the mockingbirds on the Galapagos), the biologists learned, natural selection can lead in different directions and ultimately make joint reproduction impossible: over time, such different species can emerge (such as discovered by Darwin in the Galapagos Islands). Biologists call this process, the most important in the emergence of new species, geographic speciation. Geographic speciation closely links the emergence of biodiversity on earth with its natural history: the separation of continents, the emergence of mountains, glaciers, deserts, etc., isolated parts of a species from other parts and, over time, led to today's many millions of species. It also explains the frequent occurrence of endemic species on remote islands - once a species got there, it was usually isolated from the rest of the species.

But spatial separation is not the only way to live in different environments: Species can also arise through adaptation to different ecological niches (>> more) - animals that happen to differ from their competitors in certain characteristics and can thus use other resources , thrive just as well as the original species, allowing related lines to diverge over time. This process seems to be very rare in animals, as common offspring blur the differences again and again. With plants comes the "sympatric speciation”(This is the technical term for the emergence of new species without geographical separation) due to a special genetic mechanism (“ polyploidy ”- the doubling of chromosomes). Since biologists speak of a new species when the individuals can no longer reproduce fruitfully with one another, this can of course no longer be checked directly in the case of fossils, and they have to fall back on external differences. The changes that lead to new species are gradual, new species are connected to the ancestor species via a direct line of descent from “intermediate forms”. In the case of fossils, these intermediate forms sometimes lead to long discussions about the “correct” classification, especially since the answer can vary depending on the characteristic examined. With sufficiently long periods of time, gradual changes also result in completely disruptive evolutionary news, such as the adaptation of four-legged friends to rural life or the wings of birds in the past.

Looking back at evolution, a trend towards increasingly complex organisms can be seen - from simple bacteria to humans with the most complex organ of all, the human brain (more about this >> here). Biologists do not see this development as a “targeted higher development”, but as a consequence of the ever finer adaptation to ecological niches - the niches of the small, simple living beings were occupied first. The fossil record supports this theory because they show that most of the earlier species are now extinct: adapting to narrow ecological niches is initially an advantage, as it reduces competition; but when the environment changes, ecological specialists in particular are often doomed to extinction. In evolution, only the momentary advantage counts. What in retrospect seems like a straight line development is more of an aimless search if you include the extinct species. (As far as the "higher development" is concerned, it is by no means clear that the complex organisms are "better": both in terms of biomass and biodiversity, for example, bacteria are superior to humans, and they have also lived much longer on earth.)

Coevolution and Cooperation

Since other living beings always belong to the environmental factors and the “ecological niche” of a living being (the prey for the predator, the flower for the pollinating insect), the change of any living being through natural selection is always also a change in the environment of other living beings : When beach mice become lighter (see above), it means for the birds of prey that their food is harder to find. And this means either less food or, if the variability of the birds of prey provides a basis for this, a natural selection of better sighted birds.

Evolution - corpses pave their way

If a group of living beings fails to adapt to changed environmental factors, it will die out: all species known only as fossils have suffered this fate; the vast majority of all species that have ever lived on earth are now extinct. A special case are very rapid, catastrophic environmental changes that have led to several >> mass extinctions in the past; evolution is blind to such events, which gives chance its chance (>> below).

The change of one species becomes a consequence of the change of another species Coevolution called. Darwin studied the adaptation of orchids to pollination; And today we know that many of the chemical substances that can be found in plants are a defense against predators, for example butterfly caterpillars - and that many butterflies in turn have developed adaptations to certain poisons that allow them to get away from certain plants live (with the advantage that no other species feed there). Whole ecosystems can be the result of coevolution: For example, the grass steppes are an adaptation to the herds of herbivores (>> here); and the storage of silicate structures in leaves (as protection against eating) led to the formation of thick, wear-resistant teeth in some herbivores. An extreme form of coevolution is the creation of symbioses. The emergence of eukaryotes through endosymbiosis (>> here) is an example of this. Many other symbioses shape life today: sponges build coral reefs with the help of algae, trees live in symbiosis with numerous fungi in their roots and thus get nutrients that would not be accessible to them on their own, cows can only get the cellulose in their food with help decomposed by bacteria and protists in the rumen. We humans also harbor billions of bacteria in the intestines that help digestion there.

And finally, evolution can too cooperation promote: This will prevail whenever individuals together have better chances in the “struggle for existence” than alone. The so-called extreme forms show how far this can lead Superorganisms: Species in which individual individuals take on roles that lead to a performance that is significantly greater than would be possible without this specialization. Examples are termites or leaf cutter ants: with the latter, the largest animals after the queen chop up the leaves on the trees, other animals carry them to the camp, from there still others to the nest, where they are further chopped up by one group, shaped into balls and carried along Mushrooms to be planted. The smallest ants take care of the mushrooms. There are also "garbage workers" who remove waste, "undertakers" who bury dead ants and "warriors" who defend the nest. All of this happens without central control; The "ant language" consists of a group of chemicals, the pheromones, which control the cooperation: As each group releases pheromones in a certain way or reacts to certain pheromones, apparently "intelligent" behavior arises.

Another example is the >> people who defend themselves better in a group against large animals and could only kill them together: Therefore, in people there is not only a striving for personal benefit, but also a deeply anchored sense of fairness and justice . This system enabled people to build ever more complex societies (>> more) that would not have been possible without trust in others, right up to today's global market economy (>> more). He could have gleaned Adam Smith's division of labor from the leaf cutter ants. Images like that of the “egoistic gene” do not contradict this, because process and product are not the same (see >> Beethoven error): the “struggle for existence” can also lead to peaceful cooperation and has in many cases also done so . Success is decisive, and complex societies based on the division of labor (cooperative) have historically mostly triumphed when they encounter simpler societies, which is why they predominate today.

Of course, life in a superorganism (and human civilization can also be understood as such) has consequences for evolution: Since every single individual takes on a specialized role, skills that are no longer required are also less and less developed. Domestic animals, for example, have smaller brains and less keen senses than their wild ancestors; And the individual people are becoming more and more incompetent: most of us could no longer feed ourselves (without bought tools!), protect or house ourselves. There are studies that show that the human brain has been shrinking since agriculture was invented: we made ourselves pets.

Chance and necessity

Another answer from modern evolutionary research is that of the old question of chance or necessity as the driving force behind evolution. In the beginning, many Darwinists considered adaptation (i.e. the necessity) to be the driving force of evolution; With the discovery of mutations as a source of diversity and the role of catastrophic cuts (>> mass extinctions), it became clear that chance also plays a huge role: it controls the emergence of variability. So chance and necessity influence evolution. If you set the clock back and let evolution run again, life would look very different due to the influence of random events - at least that's what most biologists believe; a convincing representation can be found in Stephen Jay Gould's book “Zufall Mensch”. Others, such as Simon Conway Morris (“Beyond Chance”), however, believe that due to the laws of adaptation to the ecological niches of the earth, life would develop in a similar direction again, natural selection would take care of that. Regardless of this question, natural selection as such is not accidental: it always selects the organisms that can best survive. In doing so, she has also contributed to the fact that the chain of life has never been broken for over three billion years.

Literature:
>> Ernst Mayr: This is evolution; a good introduction to Richard Dawkins ’" The Lie of Creation. Why Darwin is right. " (Ullstein TB, 2012). (The nicer original title is: "The Greatest Show on Earth. The Evidence for Evolution”.)

Continue with:
>> The story of life on earth

© Jürgen Paeger 2006 - 2020

See also:
Background >> Charles Darwin and the theory of evolution.

To Evolution of the whales there was a report in the American National Geographic from August 2010: >> Valley of the WhalesThere is also an appealing >> animation (both in English).

The convergence, the independent emergence of very similar forms - other examples are hummingbirds (a butterfly) and hummingbirds, both of which suck nectar from flowers standing in the air, the poisonous stings of jellyfish and scorpions or the multiple emergence of eyes - is something like the opposite the Homology (>> above), which refers to the similar basic construction plan for apparently very different parts of the body, such as the bird's wings, human arms and fish fins, all of which descend from the same organ of a common ancestor. Another example is the human lungs, which correspond to the fish's swim bladder.