Mistakes of Evolution: Unreasonable Design

The idea that living things change over time has been voiced by many long before Charles Darwin. Among the early evolutionists was not only Lamarck, but Darwin's grandfather - Erasmus. However, these ideas could not become dominant in science, since they did not have a rationalistic explanation of the mechanism of evolution. Lamarck postulated a certain aspiration for perfection embedded in all living things - a special essence, which he called the principle of gradation. Darwin found a mechanistic explanation of the process of changing the organic world, and it turned out to be very simple and understandable to the educated public of that time - natural selection.

Many contemporaries of Darwin from among wealthy gentlemen were fond of artificial breeding, creating and improving breeds of horses, dogs, pigeons. It was well known that by allowing the offspring with the necessary traits to breed and culling the unsuccessful individuals, one can very quickly change the appearance and almost any properties of the animal or plant. Darwin guessed that in nature, the same process should go on its own, similar to what happens in a kennel or dovecote. If the owner of the kennel needs long-legged dogs that can run fast, he will select long-legged puppies, then cross them and for several generations will get a new breed, say, a hound. If in a certain population such conditions arise when longer-legged individuals will catch more prey or escape more successfully from a predator, then they will have a chance to leave more offspring.

Jenkin's nightmare

How is hereditary information transmitted? In the era of Darwin, it was believed that during sexual reproduction, paternal and maternal inheritance merge in the offspring into a certain indistinguishable mass. This idea was the basis of the so-called "Jenkin’s nightmare." Speaking in the racist spirit of Victorian England, engineer Fleming Jenkin asked Darwin supporters to imagine a situation where a white man accidentally lands on an island inhabited by black savages. Perhaps, Jenkin admitted, a white man, by virtue of his superiority, will become king on this island, will take a hundred wives from local women. But can it be assumed that after many years a traveler arriving on the island will see it inhabited by white people? No, “useful” heredity will dissolve in the local population. Responding to Darwin's critics became possible only with the advent of genetics. It turned out that heredity is basically discrete, and it is quite possible that the island, in the end, would be inhabited only by whites (with the fantastic assumption that the genes of a white person give advantages when reproducing).

The post-Darwin era brought with it new outstanding discoveries in biology. The DNA structure was discovered, the genetic code was deciphered, the concept of genetic mutation was introduced, however, natural selection is still recognized as the main mechanism of evolution. And it rarely happens in science that a scientist manages to intuitively find the mechanism existing in reality, which cannot be explained with a certain level of scientific knowledge. Darwin did it.

Is evolution enough for time?

However, the question arises: was there enough time for evolution to produce so many differently constructed organisms by selecting useful mutations that have arisen randomly? Modern science gives an affirmative answer to this question. After all, if we compare the rate of evolution that we observe in the fossil record with the rate of evolution that scientists now obtain in laboratory conditions, when they purposefully force organisms to evolve, it turns out that in the laboratory it is possible to achieve speeds that are many orders of magnitude higher than those what were in nature. In other words, evolution could theoretically go much faster than it did on Earth.

Moreover, the genetic differences between animals are not so great. The further we read the genomes of different animals, the clearer it becomes how similar, how related all animals are to each other. It would seem that what is common between the legs of a fly, the tentacles of anemone, the fins of a fish and the hands of a person? And it turns out that they are regulated by the same genes.

Here you need to understand that the genome works at the level of the cell, and not the whole organism. A living creature does not have a central genome. When a fertilized egg begins to divide, each daughter cell receives a copy of the entire genome. That is, all cells of the embryo, first two, then four, then eight - the same, they all have the same genetic program. And why, then, brain is formed from some cells, from others - skin, from third - heart? All this happens due to self-organization: the cells exchange signals and change for each other the environmental conditions to which their program reacts in a certain way. And already in the early stages there is a markup. It can all start with the fact that the egg has polarity. More substances are concentrated on one pole than on the other. And when the egg is divided, then in some cells there will be more substance than in others. A high concentration of this substance can be perceived as a signal for the inclusion of a particular gene. Suppose this gene encodes a signal protein. It will begin to be produced from the cell and will be perceived by the neighboring cells as a signal along which another 20 genes will turn on. They will begin to produce 20 other signals. As a result of such processes, the embryo is labeled and different genes are included in its different parts.

How and why do genetic mutations occur?

One of the most common types of mutations arises from DNA copying errors. This system is very accurate, but there is nothing absolute in biology, and it is impossible to create a copy system that would never have been mistaken. Rarely, it appears in the DNA chain instead of the correct nucleotide of some other. The nucleotide may be skipped - a deletion, loss will occur. Or an extra one is inserted. Sometimes larger DNA changes occur due to the omission of whole pieces. This is very likely when there are repeats in the DNA. Nucleic acid molecules tend to stick together in identical pieces, due to which loops sometimes form. An enzyme that copies DNA can skip a piece enclosed between two repeats. In addition, DNA is capable of recombination, the exchange of homologous and non-homologous pieces. Two strands of DNA can break and stick together with each other crosswise. Well, of course, there is a constant exchange between DNA molecules during sexual reproduction - in each generation and absolutely purposefully. In bacteria that do not have sexual reproduction, this happens less regularly, but it also happens. Bacteria exchange DNA fragments with each other. Pieces of DNA of different origin can connect, change fragments. This recombination is the most important mechanism for changing hereditary information. And it is arguably more important for evolution than a point mutation. Due to the block combination of different pieces of DNA, the probability of getting some kind of complex trait is much higher.

Interesting experiments are devoted to this phenomenon, for example, on one of the species of worms. A certain embryo cell sets the program: there will be a tail, here a head. If you separate this cell from the embryo, you get not a worm, but a shapeless lump. But it is enough just to touch such a cell to the developing embryo, so that in the place to which we touched, a tail forms, that is, a polarity arises. But so far, these mechanisms of embryogenesis are not known in all details. Deciphered only the very basics, key regulators. We can not yet take the genome and on the computer to calculate which of this genotype will turn out the phenotype. But most importantly, it has been established that very small changes in the genome may be sufficient for radical changes in morphology.

A case in point is homeosis mutations, that is, mutations of key developmental regulators that can lead to such radical changes as, for example, the appearance of an additional pair of wings or the formation of legs instead of antennae in a fly. Even in humans, a second pair of auricles may appear on the neck, although this is more common in goats. Such a “miracle” is explained quite simply. In the development of the embryo, all vertebrates have a stage at which the so-called branchial arches are laid. In terrestrial vertebrates, the gap between the first and second branchial arches turned into the ear canal (Eustachian tube, middle ear cavity). This is followed by a few more gill arches and gaps between them. And here, homeosis mutations can lead to the fact that even on one of the rudiments of gill slits, the ear shaping program will work. Then we get the ear in the wrong place. A similar process generates, for example, caterpillars and butterflies with paws on all segments.

Each gene of an organism has passed a long evolutionary history and tested for performance; it contains a “meaningful text”. Therefore, with random combination with a high degree of probability, meaningless combinations are obtained.

Does evolution need complexity

At the moment when the first living creature appeared, the first biological replicator, the first object that is capable of producing copies of itself and which the Darwinian evolutionary mechanism can already act on, biological diversity could develop automatically. Another question is whether the growth of complexity in evolution was necessary? In principle, one can easily imagine that only bacteria appeared and at this level living things stopped. This is a very likely scenario, and it does not seem surprising that in the Universe for a thousand planets where only bacteria live, there is only one where something more complex has appeared. At the bacteria level, evolution is stuck for a long time. It would seem that nothing portended the emergence of more complex forms of life. Some believe that even the appearance of a eukaryotic cell is a terribly unlikely event comparable to the birth of life. But this cannot be verified in any way. The null hypothesis regarding the complication of the structure of organisms is as follows: there is no particular direction of evolution toward complication — a purely stochastic process, wandering, takes place. Evolving groups of organisms branch (diverge), and quite by chance during the branching, more complex descendants sometimes arise. Due to wandering in the space of complexity, there is an increase in the complexity of the most complex organism.

Patterns of being

Science cannot yet answer the question of exactly how many genes distinguishes a person’s hand from a fly’s foot. Since it is not known exactly how many genes are involved in the creation of these organs. Here we enter the field of a young and very promising discipline called evolutionary developmental biology. It began with the discovery of homeobox genes. These are genes that play a key role in the marking of a developing embryo in animals, determining which part will become the front, which back, where the back will be, where the stomach, etc. And now the complex mechanisms that control the development of the embryo are deciphered quite quickly and successfully. . The key to them is why we are arranged this way and not otherwise. Indeed, not adult phenotypes are evolving, but development programs. The fact is that there is no drawing of an adult organism in the genome. It is impossible to find encoded descriptions of the shape of the nose or instructions that the hands should be five-fingered. Therefore, ontogenesis is a kind of self-organization process, somewhat similar to the appearance of frosty patterns on glass. Sometimes there are very beautiful pictures - flowers, gardens, forests ... Where are they encoded? Somehow they are encoded in the properties of the water molecule and in the texture of the glass, in the temperature mode, that is, in the environment. The physicochemical properties of the water molecule play a role, which determine how it crystallizes. So, frost patterns are encoded in a water molecule, in the same way as a phenotype is encoded in DNA.

However, apparently, not everything is so simple. We see that those evolutionary lines that have taken the path of increasing their complexity continue to follow this path. Obviously, some positive feedbacks begin to work. The closest example is the development of intelligence, complex behavior. Positive feedback will arise if in this population the most intelligent individuals are more likely to reproduce successfully and leave the largest number of offspring. This means that the genes of a big mind are spreading and in a few generations everyone will become equally smart. If one more intelligent mutant appears, this mutation will spread again and everyone will become the same. A kind of “arms race” arises, and this is one of the most important mechanisms for escalating complexity. Usually it leads to the development of long legs, large horns, acute vision. But the arms race can also go the same way in terms of mental abilities.

Eye - quickie, brain - well done

However, the complexity of the body does not always mean its improvement. If in reality there was a “rational designer” who could afford to create a living organism from scratch, so that everything was done in the best way in it, then life on Earth would look completely different. In reality, every living creature is a lump of compromises. Genomes are very similar to program codes developed by a group of stupid hack programmers, where the patch is on the patch. It is poorly written here, but a block has been added here that fixes this error. As a result, the program works in most cases, although not in all. A classic example of such imperfection is the eye in vertebrates. Creationists often mention this body as evidence of reasonable design. As early as the 19th century, German Helmholtz, a great optician and eye specialist, saw a lot of structural defects in the structure of the eye. The eye is made extremely imperfectly. Patches, structural defects are offset by refinements and improvements. For starters, our eyes are turned inside out. In vertebrates, photoreceptors look inside the skull, the photoreceptor cell itself is in front of it. Between the photoreceptor and the light, there are also auxiliary cells and nerves that approach the photoreceptors not from behind, which would be optimal, but from the front. This design of the eye stretches from the earliest chordates. In them, the central nervous system was formed by poking the neural plate with the formation of a tube. As a result, the photoreceptors turned into the inside of this tube. For the first chordates, this position of photoreceptors was absolutely not a drawback, since these animals still did not distinguish between images, but only distinguished darkness from light. They were tiny and completely transparent, so they didn't care where the receptors looked. Later, when complex eyes began to form in vertebrates, they arose as protrusions of this neural tube. The eye became more complicated, but the photoreceptors could no longer be turned in the right direction.

Now the nerves that transmit signals from the photoreceptors to the brain must approach the retina from the outside, and then go inside. To do this, I had to make a hole in the retina, the so-called blind spot. In general, we get a very low-quality picture from the retina, but the analyzer brain corrects the situation, completing a bad image. True, it is precisely because of this that a person is subject to all kinds of optical illusions. And if at dusk we take the fold of the curtain for a hiding figure, this is because the design of the eye did not differ in particular intelligence.

The article “Unreasonable Design” was published in the journal Popular Mechanics (No. 8, August 2010).


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