Origin of life

The origin of life

Time and the increased complexity of life

The complexity of the processes that take place at the cellular level is astonishing and poses a challenge to the human mind. This complexity has not always existed, but has developed through an evolutionary process spanning the interval from time A, when no cells yet existed on Earth, to time B, when the first unicellular organisms had already appeared. The chapters of the story that led to the development of the human body and the human brain began to be written nearly four billion years ago. That entire story is recorded in each of our bodies, not as a memory accessible to consciousness, but as computational instructions whose complexity is indispensable for developing and maintaining the organization of the human body—the living instrument through which consciousness can experience the events of the psyche. Because of the limits of our perceptual faculties, and because our conscious awareness does not integrate all the unconscious functions of the brain, our own body may even appear to us as an alien entity. For centuries, human beings debated body and soul without possessing any reliable knowledge of either. Thanks to science, today we know at least something about the body, and what we have learned leaves us open-mouthed in wonder.

Information: the fundamental factor in life's development

The complexity of living organisms applies equally to human beings, animals and plants. There is no difference in this regard between a man, a cat, or a tree. There are some features that distinguish humans from animals, but for now, starting from the cellular level, let's observe how an essential element, information, is transmitted and incorporated into living organisms. For example, at a scale of some millionths of a millimeter we find small molecules composed of a few dozen atoms (the hormones) that circulate easily in our body and carry chemical messages, that is, information. But what exactly is information, which constitutes the very essence of life from its simplest to its most complex forms? It is a resource, which may be regarded as creative, through which a physical state becomes a different and more complex physical state according to an encoded rule. It has two fundamental aspects: the first, related to the processing and execution of instructions, is represented by that series of rules through which, as environmental conditions change, a system moves from one state to another. Put this way it seems to be something complicated, but we can explain it with a very simple example. Along our streets there are street lamps that turn on when ambient light intensity falls below a certain value and turn off when the light intensity exceeds that value again, so they normally turn on at dusk and turn off at dawn. They are connected to a simple servomechanism equipped with a sensor, a power supply and a switch that opens and closes the electrical circuit connected to the lamps. The information provided by the intensity of the light, that is, by ambient conditions, determines the state of the system: whether the switch is on or off. Note that in this example the operation of the servomechanism is entirely automatic, however the instrument was devised by an external intelligence that designed it in relation to the environmental conditions, the required performance, and the purpose for which it was programmed.

The other aspect concerns the encoding and transmission of information, which is represented, stored and transmitted by changes in the state of the physical medium. Although distinct from its physical support, information is affected by the physical limitations of that support, and can be transmitted correctly only if transmitter and receiver share the same code. If a person speaks, the information contained in his words is transmitted through the propagation of the sound waves in the air, or through a microphone, through the modulation of electric current, the amplifiers and the speakers: these physical media do not constitute the information, which is encoded in the language being spoken. The listener can decode the information only if he shares with the speaker the code of the spoken language: for example, if the listened heard the word burro, an Italian listener would decode it as the dairy product used in cooking we call butter, while a Spaniard would think of a donkey. Therefore, information is an extra-physical entity: it cannot be interpreted in terms of mass-energy, but is still subject to the laws of physics as it is contained and transferred through a physical support: it can be created and destroyed, and requires energy to be transmitted or used.

Let us now see how to interpret, in the light of these brief remarks about information, the transformations that have led to the appearance of the first living organisms on our planet. Avoiding, as far as possible, the highly imprecise term matter, what actually exists in the physical world is a variety of substances occurring as solids, liquids, or gases. These substances are made up of molecules, in turn composed of atoms bonded together, and atoms are made of energy organized according to certain rules. A living organism is not the result of accidental combination of the substances that constitute it. The fact that our body consists of large amounts of hydrogen, oxygen, carbon, nitrogen, calcium, with a handful of phosphorus, potassium and magnesium and a minimum dose of iron, iodine and other elements, does not mean that the right doses of all these substances are enough to make an organism: it is also required an enormous amount of information that has been generated and incorporated into living organisms during those four billion years of evolution that we referred to earlier. If we compare atoms to the letters of an alphabet, and the molecules of the substances we are composed of to words formed with those letters, it is possible to have an idea of the meaning of the whole story only through the information contained in all the paragraphs of the story, starting from its beginning. A film viewed frame by frame would show an evolution in which each frame reveals the existence of more complex systems than those in the previous frames: that is, systems involving a greater amount of information incorporated into them and functioning within them.

Hypotheses on the origin of life

The picture that science gives us of how this process began is roughly as follows. In a particular environment, at a certain point in time, energy conditions were such that some substances, composed of simple molecules, combined to form more complex molecules. Each of these new molecules, which had not existed before and from that moment onward came into existence, represented a new substance, a new word in our story, and thus a system containing new information. Taken together, however, these new substances brought about environmental changes that allowed information to advance to the next level. Even more complex molecules were then produced, incorporating all the information accumulated at the previous levels, and these, in turn, further modified the environment. One example of this process is the appearance of oxygen in the Earth's atmosphere. Today neither human beings nor most animals can live without oxygen, yet until about two billion years ago this element was present in the atmosphere only in very small quantities. Vast numbers of unicellular cyanophytic algae inhabiting the planet's waters produced oxygen as a by-product of photosynthesis, and this oxygen was later used in the evolution of animals for energy production.

We have seen that information transmission is determined by environmental conditions, and that the information is transferred within an organized system immersed in those environmental conditions. This is true for the simplest precursors of unicellular organisms as well as for the human body, which is a protected system surrounded by an environment with which it continuously interacts: it is clear that the life of the body depends on environmental conditions. The transmission of information in the physical world required time and energy: it took more than one billion years to bring about the first prokaryotic unicellular organisms, while nucleated cells made their appearance about 1,400 million years ago and multicellular organisms around 600 million years ago. The information in the system determines the system's potential for development, but environmental conditions, which have a variable and random character, can favor or hinder such development, or limit some aspects of it. For example, even if the seed of a plant contains all the information necessary for the plant's development, a seed transported by the wind may either end up in a place where environmental conditions (humidity, temperature, soil) favor its germination (though a bird may always come along and eat it, or an ant can take it away), or in another place where germination cannot occur. If we then consider the seed as an individual, that is, a closed system, we see that even if the information that determines its development is embodied within it, it depends in part on the external conditions in which the system finds itself. And this also applies to the plant's entire subsequent development.

Organisms as information systems: the source of information

The progressive complexity of living organisms, considered as systems in which an increasing amount of information is embedded, leads us to ask whence this information originates. It does not matter what name we want to give to this process, that is, the label we put on the jar: we are interested in knowing the contents of the jar. The label may read creation, or nature, or evolution, or chance, according to one's preference, but what we are interested in understanding by examining the way in which information was transferred into the physical world, thus giving rise to the evolution of life on our planet up to the level of human beings, is the source of information. The main processes that characterize a cell are: the presence of a closed boundary (membrane), which separates the cell's interior from the environment; the exchange of substances between the internal organization of the cell and the environment, and the consequent growth of the cellular organism; the ability to reproduce, and therefore multiply, once it has reached a certain size. The level of organization of the cell and its membrane is significantly higher than that of the outer environment: the environment, however, must have the appropriate conditions for the cell to survive, otherwise the cell would be destroyed. These requirements essentially consist of the presence of certain substances and the availability of energy within a range compatible with the needs of the cell.

It is evident that the processes that occur within a cell operate in a manner that may be described as intelligent, in the sense that they are programmed. Even the most automated industrial plants, designed by human intelligence, have a lower level of complexity compared to the processes that occur in a single cell. Human intelligence is able to conceive and design automatic systems that are, within certain limits, similar to those operating in the cell, but these systems exist and operate, even autonomously, only because they are designed and built by humans. Cell operating systems are certainly not designed and built by human intelligence, so there are two possibilities: either between time X, in which a particular system did not exist, and time Y, in which that system had become fully operative, there was a form of intelligence, outside the physical dimension, endowed with the power to progressively transfer information within the physical system; or all the information was already present in the universe, in potential form, from the very first moments of its existence (the so-called big bang). This potential, existing outside time, would be transferred into the physical world with the passing of time: between time X and time Y, an evolutionary process unfolded whose potential was already implicit in all the elements and factors present in time X, but for whose actualization it required conditions different from those existing at time X.

Information as a creative essence and as the basis for intelligence

In both cases information is the quintessence of creativity, the indispensable premise for the existence of what did not exist before. Indeed, the second hypothesis too implies a constant increase in order and information within closed and defined systems, and therefore requires a wider understanding, and perhaps a redefinition, of the concept of intelligence. In fact, even in the case of automation systems produced by human intelligence, we can always locate a time X in which there is no trace of such systems, and a time Y (following X) in which such systems have been realized. At time X, it was not possible to conceive or design such systems, not because of a lack of intelligence, but because of the lack of resources or knowledge required for their realization. This is the reason why, for example, computers – so widespread in our days – could not be realized a century ago. On the other hand, the origin of the same human intelligence remains a mystery to us, since none of the animal species other than man shows, even at a reduced level, the skill to understand, conceive, design and build, that we can find within our species, where however only some of the social organizations and cultures have developed the intellectual faculties at a level adequate to the design and realization of technologically advanced products. And even in these socio-cultural systems, not all the individual intelligences are at the same level, but relatively few are able to conceive, design, organize and manage complex systems, while most people act as support workers, and some even show hostility to the system itself.

Vital intelligence and human intelligence

At a basic level, in the organic sphere, a cell can operate, grow and reproduce equally well, whether it is part of the organism of a worm, a horse, a human being belonging to a primitive culture or a scientist with in-depth knowledge of cellular biology. As for the origin of the complex internal organization of the first cells, this is a process that developed over hundreds of millions of years: an incomparably long time when confronted with those required by the processes of ideation, design and realization by human intelligence. It seems obvious that a very close relationship between the variations in time of Earth's environmental conditions and the implementation of the processes that led to the development of life should be assumed, since the same billions of years have passed on other planets without any evolutionary process, similar to what led to the emergence of life in our world, occurring on them. For this reason Earth, within the solar system, can rightly be defined as a living planet. However, we must keep in mind that in developing an interpretive scheme of what happened on Earth in the oldest geological eras, we can not always rely on certain and objectively verifiable data, but we must also refer to hypotheses that could have a high degree of reliability. Sometimes there is a wide gap between what actually exists now (the cellular structure with all the processes that occur in it) and the hypotheses suggested to explain the evolution of the processes that led to the formation of protocellules starting from the first organic molecules. Virchow's assertion, made in the nineteenth century, that «every cell originates from another cell», obviously cannot be infinitely backdated, and it is assumed that there has been a period of time, more or less long, in which several components of the present cellular structure interacted with each other without the existence of true cells.

We are not in a position to follow the process in its progressive development from the beginning, but we have to rebuild the path that has led to the present complexity starting from initial conditions which were such that, if hypothetically a conscious but unaware observer present at that time had been able to perceive them as a whole, not even with the most wild fantasy he could have imagined a development like the one that then occurred. The original environment of the Earth, at the dawn of its history, did not have anything in it that would foretell such an astonishing future: who could predict that from the progressive cooling of that chaotic and magmatic world could emerge a land surrounded by seas and swarming with living organisms? It is true that between these two scenarios a period of billions of years passed, but in the same span of time, as I said, on other planets nothing like that happened. Given that evolution is not a foregone conclusion in a planet's history, some scientists think that in the case of the Earth certain particular environmental circumstances occurred, which could not help but give rise to all the series of subsequent events. This conception considers the development of life on Earth as the necessary and automatic consequence of the original situation, represented by the size and composition of the Earth, the presence and composition of the atmosphere, the size and distance of the Sun, the motion of the Earth around the Sun, and so on.

So, as I have already noted, we must necessarily assume one of the following two hypotheses to explain the process that has led to the appearance of organic life: either the intervention, at least occasional, of external entities gifted with a form of intelligent energy that was transferred to the Earth system, determining an increase in organization and information in it; or, alternatively, the attribution of a form of intelligence to the process itself. In fact, if we attribute a certain level of intelligence to humans and then we want to derive our origin solely from the evolutionary process, we must attribute to the process itself all the qualities we have and also those that will emerge in the future through the progress of evolution.