The problem of the origin of life

THE MOST COMMON OPINION

What we will present in this paragraph is not the only hypothesis proposed by the scientific world, but it is by far the most accepted and widespread; in the numerous school texts that I got to know, then, is the only one presented and, You can say, is paired with Darwinism: for these reasons our criticism and our attention will focus on it. This opinion on the origin of life is generally not indicated with a specific name, we will call it “abiogenesis from primordial broth”, to indicate the most salient features.

The way it is usually described and the trust it usually places in scientific books, make that for many (even among teachers) it is not a hypothesis, but a truth now more or less proven. It will be necessary, then, try to present it objectively, to see in what experience is supported, in what it is still a simple hypothesis and in what else it contrasts with the scientific data available.

After this scientific work, we will pass (in the next chapter) to some cultural aspect connected with the theory itself.

The four statements that we list immediately below, form the basis of abiogenesis from primordial broth (which from now on, where not necessary, we will simply denote abiogenesis). Their critical examination constitutes the basic outline of the remainder of this chapter.

Statement No.. 1. The atmosphere of the primitive Earth, at the beginning of its cooling, it was different from the present one; in particular it was rich in hydrogen (H2), water (H2O), methane (CH4) and ammonia (NH3), while he was absent, almost, molecular oxygen (O2).

Statement No.. 2. The electrical discharges of the storms that occurred, the sun's rays and more, they determined the formation of various organic compounds, including amino acids (i “bricks” of cells). These organic compounds were carried by the rains into the oceans, where they accumulated, also due to the fact that there was no free oxygen (O2) capable of demolishing them.

Statement No.. 3. In this so-called “primordial soup” (O “primeval soup”), among the many molecules that have formed, there has been some similar, if not the same, all proteins, to nucleic acids and other substances that make up current cells.

Statement No.. 4. At some point, casually, the right molecules have been found and aggregated, suitable to form an initial cell simpler than the one we know. From this initial cell, by evolution, today's cells are derived first and then, from these, all other living beings.

Some supporters of abiogenesis propose the various stages of the process with certainty, others alternate expressions like “ours is just a hypothesis”, with other opposing ones, in which they manifest a more or less accentuated security, perplexing the attentive reader, to which it is difficult to summarize the thought of these authors. Others still, finally, while showing sympathy for abiogenesis, they present the facts with honesty and consistency, openly declaring the still unsolved problems and the limits of the theory. F. Crick, one of the two discoverers of the structure of DNA and Nobel laureate 1962, belongs to this category of scientifically correct people, who know well how to distinguish experimental data from their own interpretative and philosophical choices. In the book entitled “The origin of life” he is very balanced. even if in the end (pp. 149-153), scientific language set aside, gives vent to his cultural inclination, framing abiogenesis in a world view from which we feel we totally disagree.

Even Dyson despite some too optimistic expressions, clearly shows the great scientific limits of abiogenesis, despite being a staunch supporter. Balanced is also the cap. XIII, concerning the origin of life, of the work of G. Montalenti, “Evolution”.

With Crick, while belonging to opposing cultural fronts and supporting hypotheses in clear opposition, when it is necessary to define what science says, we basically agree: and this scientific harmony we hope that it can also be realized with many Italians culturally deployed on fronts other than ours.

Crick, despite having his own particular vision of the origin of life, substantially remains in the setting of the abiogenists that we have exposed. Ultimately, indeed, he accepts that life may have originated on earth from the primordial soup, although he thinks it more likely that that process took place earlier on another planet, from which then highly evolved intelligent beings would have sent us the germs that fertilized the primordial terrestrial broth. E’ inclined to move the phenomenon elsewhere, but the four fundamental affirmations of abiogenesis are fully shared by him.

There are not a few who, listening to our anti-evolutionist arguments, they consider us (at least) blinded by particular extrascientific prejudices. To these people we highly recommend Crick's book (and also that of Dyson): when these two authors expose the limits and problems of abiogenesis, it will be difficult to make the same accusations that are sometimes leveled at us.

THE PRIMITIVE ATMOSPHERE

The current atmosphere, below the 10.000 meters high, it has an almost constant composition and is mainly made up of nitrogen, (about the 78% of dry air) and oxygen (about the 21% of dry air). Water vapor is present in variable quantities and carbon dioxide, although very important, it is in low percentage (0,03%).

This atmosphere cannot produce organic compounds (carbon based) necessary to constitute living beings and even if it formed a small amount, the presence of oxygen would consume them, with a process similar to that which occurs in a stove, albeit slower.

Those who believe in abiogenesis must therefore assume a composition of the primitive atmosphere different from the current one, that is, rich in hydrogen, methane, ammonia and very poor in oxygen: but that the primitive atmosphere was just like that, it is an assumption or a proven fact?

This is how he expresses himself Crick:

“It was once thought that the primordial atmosphere of the earth was very different from the current one. Given that hydrogen is by far the most abundant element in the universe, it was natural to believe that it predominated in the original atmosphere … Lately, however, these ideas have been questioned. Hydrogen is so light that the Earth's gravity is not enough to hold it back so it tends to escape into space … Now it is plausible to think that much of the hydrogen present at the beginning escaped so quickly that it was never a predominant element of the atmosphere … Today it is stated that, based on experimental data obtained by averaging all available rocks of a certain age, the atmosphere of the past was not very different from the present“.

The doubt remains as to what the atmosphere was like before the oldest known rocks were formed but, Crick says again, “it is difficult to come to reliable conclusions on this problem. The temperature of the primeval earth is also uncertain”.

Therefore it is not the composition of the primitive atmosphere that suggests it is possible that abiogenesis actually occurred, but on the contrary, it is the belief in abiogenesis that suggests a particular primitive atmosphere. Often the exhibitors of abiogenesis do not clarify this point and bring as evidence what is actually a presupposition, not only unproven, but that contrasts with the data available so far.

 

COMPLEXITY OF THE CELL AND ITS COMPONENTS

The cell: an unimaginable complexity

Who describes the spontaneous formation of cells, which are the most basic form of life, often does not make clear their extreme complexity and the fact that the simplest form of life is the most complicated mechanism known.

Viruses could be carried as simpler living things than the cell, but they can only live inside the cell, outside of it they are unable to perform any function. E’ in the cell, therefore, that the phenomenon we call life takes place.

Some cells are defined “easier” (bacteria and blue algae), because they lack certain structures, but these cells perform the same functions as the other defined ones “more complex”, and with the same chemical processes. Indeed the bacteria, as a whole, they manage to do many things that others cannot: they live in almost boiling water, in the ice, in oil wells, in nuclear reactors (that is, in the presence of deadly radioactivity), they know how to synthesize organic substances using various chemical reactions (by it. burning the sulfur), they produce vitamins, etc.. There is therefore no one “simple cell”. The cell, like a car, it exists in its totality, or it doesn't exist.

E’ difficult to describe the complexity of a cell because man has not built anything that can be compared to it. The best equipped chemical laboratory is as if it barely knows how to make auctions, in comparison to the poems he can compose a cell: just think of photosynthesis. The biggest construction company is a bunch of incompetents compared to what a cell can do: just think that it, receiving only nourishment from the outside, manages to build an entire organism; indeed a dog, an oak, a flower, they all originated from a specific cell, which trained them for their exclusively internal organizational capacity. The largest electronic brain is child's play compared to the human one, also derived from a cell. And which machine is able to build another machine equal to itself, that is, to reproduce, how does the cell? Its complexity therefore goes beyond our imagination.

Comparing the work of a cell to that which takes place on a construction site, we can say that she knows how to be an architect, as it has in itself (in the DNA of the nucleus) all the instructions necessary to perform the various functions. But he also acts as a foreman, because it has mechanisms that are able to make the right operations execute at the right time (through RNA and the various regulatory systems) e, finally, he also acts as a worker, performing various tasks mainly by means of proteins: nails, hair and muscles, to make just a few examples, they are made of such substances. Proteins and DNA are the two extremes of cellular organization and it will be useful to briefly see them in more detail.

Complexity of proteins

Proteins are made up gives 20 amino acids (or amino acids) several that connect to form long chains. The simple bacterium of Escherichia coli contains about 2.500 types.

Knowing that proteins are made, on average, gives 500 amino acids, if we were to write those of Escherichia on sheets, indicating i 20 types of amino acids with 20 different letters of the alphabet, there would be a long composition 3 times the Divine Comedy.

The amino acids that form proteins, in turn, they are done gives 4 types of atoms: carbon, hydrogen, oxygen and nitrogen; some also contain sulfur or phosphorus. They are produced by living beings, or in the laboratory, but they do not form by themselves. If we wanted to compose them starting from atoms, it would take a minimum of 10 (for the amino acid glycine) to a maximum of 27 (for tryptophan): naturally of the right composition (5 hydrogens, 2 oxygen, 2 coals and 1 nitrogen, regarding glycine) and in the right arrangement. If the atoms that make up glycine we connect them in a different way than prescribed, we don't get glycine, but something different: it would be like swapping letters in a word. “Preceded”, for example, does not have the same meaning as “procedures”, ne of “producete”; combining the letters freely, then, most of the words wouldn't make sense (come “pordecute”, etc.).

I know, after composing the amino acids, we also wanted to continue with proteins, we should do a work similar to that of the typographer when composing the pages of a book.

In conclusion, to make a protein in the laboratory, we should get the right atoms, connect them in the right way, and first do the whole series of 20 amino acids. We should then take the right amino acids and combine them in the right way. After doing this difficult job (impossible to do in the laboratory, without the guidance of organic compounds produced by cells), we should keep the delicate structure in the right temperature conditions, acidity, salinity, etc., so that it is not irreparably damaged. Five right choices that highlight the obstacles to overcome in order to form and preserve a simple protein. All these obstacles, if we want to remain in a scientific context, they cannot be bypassed simply by stating that, somewhere, somehow, a long time ago, the current proteins of the cells were formed and preserved.

Complexity of DNA

If we wanted to build DNA, the first grouping to be made would be the four nitrogenous bases, often referred to simply as A (adenina), T (timina), C (cytosine) and G (guanine). To make each of these bases, we should take about thirty atoms of 4 different types (i.e. carbon, hydrogen, oxygen and nitrogen) and connect them together in the right way. We should then prepare a special sugar, deoxyribose (compound gives 5 carbon atoms, 10 of hydrogen e 4 of oxygen, wedged in a precise arrangement), and phosphoric acid (phosphate). These three starting compounds then go together in the right way, to get the 4 nucleotides corresponding to 4 bases (adenin-nucleotide, timin-nucleotide, citosin-nucleotide e guanin-nucleotide).

I 4 nucleotides, finally, they must be fitted two by two (adenine-nucleotide with thymin-nucleotide and cytosine-nucleotide with guanin-nucleotide) and the couples must be arranged one above the other, forming a kind of ladder.

To give an idea of ​​the difficulties encountered when we try to randomize the reactions necessary for the formation of DNA, we will consider the composition of a nucleotide starting from its three constituents (nitrogen base, desossiribosio and phosphate).

The abiogenist Dyson puts it this way:

“If the bonds are formed at random, out of a hundred molecules only one will be well structured from a stereochemical point of view. E’ however, it is difficult to imagine a natural process capable of capturing that single nucleotide, properly formed, among his ninety-nine defective brothers! The good nucleotides, finally, they are unstable in aqueous solution and tend to split again into its components“.

In the bacterial cell, DNA consists of several million pairs of nucleotides, while in man there are a few billion in each of his cells (all cells in an organism generally have the same quantity and quality of DNA). If we have resembled the proteins of a cell to the Divine Comedy, it is permissible to resemble DNA, formed by many more elements, to an encyclopedia.

While proteins are made with a 20 letters (like ours), DNA is made to a similar Morse code, and a 4 signs. E’ task of another type of compounds, the ANNs, translate language a 4 signs in language a 20 signs, that is, to form proteins based on the instructions of the DNA; but how this is possible is too complex to be addressed here.

ELECTRIC DISCHARGES AS MOLECULES BUILDERS

In 1953 Miller subjected to electric shocks, for a week, a mixture of hydrogen, water, methane and ammonia and obtained “a mixture of small organic compounds, including a fair amount of two simple amino acids, glycine and alanine, present in all proteins”.

Not infrequently Miller's experiment is reported saying that they are formed in it “amino acids” (and not two simple amino acids), “which represent the building blocks of proteins, fundamental components of living matter”. This way of exhibiting neither takes into consideration the obstacles to overcome in order to gather amino acids into proteins (see previous paragraph), nor those (infinitely larger) to move from proteins to cells, which we will see later. The reader is given the deceptive impression that life has now been reproduced in the laboratory, almost! So let's see in detail the limits of Miller’s experiment.

As we noted earlier, the atmosphere present in the Miller apparatus is supposed to be similar to the primitive one, but this is far from proven. On the primordial Earth, hydrogen “it would have dispersed into space, while in Miller's original experiment, which took place in an isolated system, each molecule of hydrogen, once formed, could not move away from the system and therefore accumulated as the experiment continued”.

The fact that the two simplest amino acids were formed and not the others 18, also present in all living beings, it could also prove that, that way, you go not far. If I give a child a pen, of the sheets, a pair of scissors and some glue e, among the various doodles, I individual two of the 21 Alphabet letters, can't exclaim that, by dint of having to write at random, cut with scissors and glue, a novel or a scientific treatise can come out. Miller's experiment, therefore, it shows very little.

If with other experiments a more effective way to produce amino acids could be found, there would be other problems to solve. For example the fact that, in addition to 20 amino acids constituting proteins, there are still some 150 not protein which, if mixed with others, they would create a further obstacle, almost insurmountable, to the formation of the right proteins. It would be as if you wanted to randomly compose a book in Italian, drawing the letters of the alphabet from a sack where there are also the letters of others 7 different alphabets!

But the problems are not over. All amino acids, except the simplest one (wisteria) they are asymmetrical. They resemble, that is, to the hands: these are made from the same elements, but the individual parts (day) they are arranged differently, so the left hand does not fit the right glove and vice versa. The two hands are said to be specularly alike, because one hand appears the same as the other seen in the mirror. Amino acids also exist in two mirror-like forms, this “L” (levogire or sinistrogire) e “D” (destrogire), and when they are formed at random, out of the cells, half of one type and half of the other type are formed. Instead “all the fundamental molecules, in all organisms, they have the same direction”. This uniformity amazes why it is “at the same time arbitrary and complete”. In other words, in living beings the compounds of both verses could be present, or there are living beings with one direction and others with the other (as their random formation would suggest), on the other hand, all the compounds of living beings present themselves with only one direction. In particular, “all the amino acids that make up proteins … are from the L series”, and glucose “it has the same right verse everywhere in nature”.

All the difficulties, for those who do not believe in abiogenesis, they are proof that it could not have occurred. For others, instead, they are proof that life originated from a single primordial cell, formed randomly, which then transmitted the same pattern to all living beings. Abiogenists recognize that it is difficult for a cell to form spontaneously, but difficult, they say, it does not mean statistically impossible. E’ necessary, therefore, interest us a little’ statistics.

BEWARE OF STATISTICAL DECEPTION

In order not to burden the subject, let's start with an allegory. A judge had to deliver the sentence concerning one of the top managers of the football pools, accused of allowing a scam. A close relative of his had made 13’ ten times in a row, playing a single card of two columns at a time. It was scam or just plain luck?

The defense attorney thundered menacingly; “You cannot condemn a person when you know that, albeit very difficult, it is possible to do '13’ per 10 times in a row“.

E, to better corroborate his argument, he had called a statistics professor, with whom he began to discuss publicly. “E’ possible, teacher, do it twice in a row '13’?” the professor, before the judge, He answered: “E’ possible“. “E’ possible to do '13’ five times in a row?“. “E’ possible“. The defense attorney arrived, finally, to the crucial question: “E’ possible, teacher, fare ’13’ per 10 times in a row?” The professor answered again: “E’ possible“. “We must at least“, the lawyer concluded satisfied, turning to the judge, “give the accused the benefit of the doubt; e si sa che, in uncertainty, it is a duty to absolve“.

The judge stayed a while’ perplexed, common sense told him that the accused was guilty, but that statistic confused his ideas.

After a while’ reflecting again he called the professor again and asked him: “What is the likelihood that a person will do '13’ per 10 times in a row, playing only two columns?”

The professor replied: “E’ as if, in an ocean of white balls, there were only of them 10 black. and a blindfolded person, pulling his 10 random balls, fish all the black ones“. But the judge was still not satisfied e, losing his temper he asked: “According to statistics, then, when you could be sure of the scam? After, 100, 1.000, 10.000 times that one makes 13’ continuously?” The professor, seraphic, He answered: “May, judge, you can never be sure“. “But“, the judge continued more and more irritated, “lei, how do you decide in cases like this? Fingerprints too, then, they do not give certainty!” “Well“, concluded the professor, “generally a limit of probability is set, beyond which the event can be considered certain. E’ clear that, if it did not do so, any decision would be impossible, and even the fingerprints would not give the definitive proof“. The judge returned home thoughtfully: convict the accused or resign as a judge?

We have proposed this illustration because everyone will have to emit, towards the theory of the origin of life by abiogenesis, a similar sentence, and we must be careful not to be deceived by unclear statistical speeches. Whoever wants to use the argument of the possible correctly must also quantify the probability that a certain phenomenon has to occur. Otherwise, guessing a single football match is put on the same level as doing “13” a thousand times in a row: logically both things are possible.

Fernando De Angelis