Evolution of life

The evolution of life

Evolution and environmental changes

In considering natural laws, starting with gravity or electromagnetism, we have to recognize the existence of something that determined the validity of those laws and not of different others. The very complexity of natural phenomena evokes in our minds the activity of forces that seem to have an intrinsic will in directing the course of events. When evaluating the dynamics determined by these forces, we can only follow the processes of our mental activity, which seeks to build a vision of the world that can be, at a specific historical moment, as coherent as possible with the acquired knowledge. This also applies to the evolution of life, which we try to interpret through an inductive process based on the information and data offered by various scientific disciplines.

In the page on the origin of life we have seen how the first unicellular organisms date back to over three billion years ago, so – how wonderful it may seem to us – nature's creative work required a long time. Earth, as we know it today, is a well-diversified environment, whose surface is swarming with living beings: every organism is like a microcosm, within which complex tranformation processes are accurately performed. But the length of the times required for the evolution of living beings should not be deceiving, leading us to think that it is an automatic process in constant and uniform progression. In the physical world, inanimate matter and life seem to be governed by different laws which, while not in contrast, are not even in complete harmony with each another. Often, in fact, the conditions of the physical environment are modified in such a way as to threaten or destroy living organisms, and at the same time new life manifests and develops where the environment shows favorable conditions. Living organisms have evolved so that they can react intentionally to environmental conditions, and not only passively undergoing them. There are physical events, such as a volcanic eruption, an earthquake, the fall of a meteorite, which modify environmental conditions in a short time and in a traumatic way, destroying most of the organic forms living in a certain area. But when environment changes at a slow pace, living organisms can activate their resources, or develop new ones, to adapt to the changes. The most obvious aspect of this capacity is movement, through which many organisms try to transfer from an unfavourable environment to a more advantageous one. But even non-moving living forms, like most plants, do have proper resources to react to environmental changes.

Mechanicism and evolutionary programs

The process that led to the origin of life, up to the formation of the first unicellular organisms, can be interpreted, in the light of reductionist theory, as the interaction between the environmental variations that have occurred on Earth with the passing of time and the progressive transfer of information, more and more complex, within certain individual forms, without any intervention by entities outside the process itself. To support this hypothesis, however, we must recognize that all information should already be present within the Earth system at the potential state: the passing of time becomes the condition that makes possible the transfer of information within the organisms, through environmental changes. Even with these premises, the process suggested by the reductionist theory implies a high level of automatism, since all transformations should only occur within the framework of the laws of physics and chemistry valid for the inorganic world. In the evolution from single-celled to multicellular organisms, however, we can see the emergence of a new function that undermines the reductionist interpretation. Already within the most advanced unicellular organisms, it is possible to observe a series of transformations and movements in the aquatic environment in which they live, movements that can be aimed at a purpose such as feeding or avoiding a danger (i.e. an environmental condition that jeopardizes the proper functioning or the integrity of the organism). To be coherent, a rigid reductive theory should extend the automatism of the interactions between the organism and the environment even to these forms of behavior: the complexity of the information obtained means that what we ingenuously interpret as finalized movements is nothing more than a consequence of physical laws and chemical reactions that intervene within the organism and between organism and environment.

Not only these rudimentary forms of behavior, but also the reproduction of primitive unicellular organisms imply the execution of what we can now define as real programs, enclosed within the organisms. External (or internal) environmental conditions trigger the execution of a particular program, but all the program's instructions must already be present inside the organism. In the case of reproduction, the external conditions are almost irrelevant – in the sense that it is sufficient that they do not inhibit the process – while the internal conditions, such as the cell's level of growth, are important for activating the program. In any case, there is a huge leap of quality – which makes a rigorous reductive theory untenable – between a system based simply on a series of physical and chemical interactions between an external environment and the interior of a certain structure, and a system which involves the transmission of programmed instructions (with an high information content) inside the structure itself. In case, one can only admit the possibility that the intelligence necessary for the transmission of high-level programming information within the organisms is determined by the system as a whole, governed by the laws of physics and chemistry associated with it. At this point, it is almost irrelevant whether this form of programming intelligence is attributed to entities outside the system or is associated with the system: it is the same unfolding of the programming effects, in their evolutionary development, which implies a form of intelligence. The organization of life can not be explained solely by matter and energy, but it also requires a transfer of programmed information that must necessarily have a source.

Intelligence as the foundation of programming

Today, we have informatic systems such as computers that give us a good idea about how a program works, first of all distinguishing between hardware and software: although the hardware is essential to make the software run, it is only the last that contains the programmed instructions which allow us to get what we want. However, each program works only if there has been a form of intelligence that has defined and ordered the instructions that must then be carried out by the machine. In addition, as it occurs in the evolution of life, computer programs also evolve, in the sense that more and more complex programs are able to work by integrating within them other programs of a simpler level, but that perform the needed instructions to run complex programs. So, in just over sixty years, in the field of informatics science, we have shifted from the programming alphabet to increasingly advanced languages, capable of making computers perform operations of considerable complexity, creating stunning effects, such as in today's most evolved video games. Even in this case, who could have imagined such a development only a century ago?

Colonies and cellular societies

Returning to life evolutionary process, some 700 million years ago some unicellular organisms began to aggregate in colonies and establish mutual relationships, until they became interdependent. The colonies then turned into multicellular individuals, inside which the cells took the path of differentiation and specialization, thus giving up the possibility of living independently. Since on Earth a myriad of unicellular organisms, whose life is complex (they move, react to the environment, reproduce, feed, and expel waste), are still thriving, we wonder why some unicellular organisms would have the need to to join together permanently, if they were able to survive by themselves? And why then would they diversify within the colony, losing every chance of an autonomous individual existence? The formation of multicellular colonies and the subsequent diversification of the cells within them, with the formation of early rudimentary neural systems, show the development of new interaction and programming elements: it is as if some unicellular organisms decided to aggregate, although they could continue to exist as autonomous individuals. It may be that at some point a mutation of the genetic code has prevented the daughter cells of a unicellular organism from separating completely and lead an autonomous independent life, forcing them, so to say, to live in a colony. However, it remains to be seen how these colonies have not continued to grow in a chaotic way, but have begun to transform themselves into organized multicellular individuals.

The classical theory of evolution

The interpretation of life evolution that has prevailed over the last decades was based on the random variations of the genome (that is, the genetic code) called mutations: these are errors that occur in the copying process during the genome replication. The replication process is very accurate: it was calculated that the statistical error probabilities are approximately one every billion replicate nucleotides. As the human genome contains about three billion nucleotides, this means that at each replication there are more or less three errors, that is, three nucleotides may be replaced by others. As is well known, the nucleotides present in the DNA are four, indicated by the letters A (adenine), C (cytosine), G (guanine) and T (thymine), so the mistake consists in replacing the correct nucleotide with one of the other three. The main task of the nucleotides is to encode, in groups of three (triplets), the assembly of the 20 aminoacids with which the long chains of protein macromolecules are formed. For further information on this process, please refer to specialized texts or websites describing the genome's functioning. Here we have just to remember that some triplets are redundant (that is, coding for the same aminoacid), that genome instructions are in part exceeding, and that a good part of the genome seems to have only control functions (regulatory sequences), encoding no assembly: so in most cases replication errors do not have any noteworthy consequences. In some cases, however, consequences occur, and they have almost always a deleterious effect on the organism's cells.

The classical theory of evolution simply states that when a mutation produces something new that leads to an advantage in the competition for survival and reproduction of an organism, it is transmitted to its offspring in accordance with the laws of heredity: so the progeny acquires that advantage, reproduces more easily, and in a relatively short evolutionary time the mutated species gains the upper hand over the not-mutated organisms. It is now worth pointing out how in biology is at work a disposition of the human psyche to explain complex and largely still unknown processes with simple and elegant mechanicistic theories, elaborated on the model of those proposed in classical physics. But, apart from the fact that classical physics was replaced more than a century ago – and therefore, even in the field of physics, the space for simple and elegant theories is limited – biology is a field of science in which complexity and unpredictability are always present. So it is best to be cautious with too simple evolutionary theories, which may contain a core of truth, but are not able to explain the complexity of all the phenomena, especially in the light of the latest researches. For instance, a surprising result is that there are only a little over 30,000 genes (a few more than the number of genes in a mouse) in the human genome, and that for more than three quarters human DNA encodes neither proteins nor RNA. That is why current biological research is engaged in trying to find out what this seemingly superfluous DNA is used for.

The current picture of natural evolution

Without going into the fascinating field of investigation of informatics biology, with all the challenges that its complexity entails for human intelligence, it is important to highlight some aspects that emerge from the picture of natural evolution. Observing the various ecosystems as a whole, before the appearance of humans and their artifacts, we can see that there is a substantial and surprising balance by which energy is utilized in an advantageous way, and the increase in information is commensurate with the available energy resources. But within this harmonized framework, it emerges immediately the need to destroy over time what has been produced, to replace it with new material. Not only does every organism constantly change, replacing the substances it is made of, but the living organisms stop functioning at some point, transforming themselves into organic matter to be used again for the life of other organisms. In this respect, the natural process does not show the least interest in what we humans would call the destiny of the single individual: in many animal species a lot of organisms are born just to be destroyed shortly after birth or at a young age. Moreover, some species have specialized as predators which, in order to live, need to destroy the lives of other animals. Plants, also made up of living matter, are anyway the basis of the food chain of the animal world. Except for the simplest evolutionary stages, all animals feed on organic matter produced by plants or taken from other animals already dead or killed. Only in plants the evolution has developed programs that make possible the production of living organic substances from energy and inorganic substances.

We can therefore observe how the evolutionary creativity of natural forces – meaning as such those who produce the increase of information necessary for the development over time of the complexity of life on Earth – lacks any form of participation that we humans can define as protective (or even affective) towards the single individuals produced. At the same time, it must be recognized that every individual is more or less endowed, at least from a certain stage of its development, with resources to keep itself alive for a certain period of time and to reproduce, resources that are expressed in the form of will, experience and strategies for surviving and mating. These resources are much more evident in the most evolved animals, equipped with a well developed nervous system, than in plants or inferior animals. With our naive, raw and inadequate human language, we sometimes refer to the dynamics in the world of nature, and in particular in the animal kingdom, calling them the law of the jungle or the law of the strongest, or the struggle for survival, defining most fitted the organisms prevailing in the competition at the expense, directly or indirectly, of the unsuccessful. But if it is true that sometimes certain natural environments actually show the requirements of an arena in which the contenders challenge directly to feed or mate, more often the causes that determine the success or failure of an organism in the evolutionary scheme are manifold and complex, such as to escape the direct control of the single organism itself, as it happens, for example, in the case of genetic mutations or sudden environmental changes.

A creative process devoid of consciousness?

Another bewildering aspect, at least for us human beings, of the evolution of life interpreted in the light of the reductionist theories, is that until the appearance of human consciousness no other form of consciousness is conceived to be able of watching a process so complex and magnificent: for hundreds of millions of years, the evolutionary creativity would produce an exceptional show, such as that of the transformation of life on Earth, without anything or anyone being able to at least perceive what was happening. One could argue that there has always been a witness, represented by the more or less rudimentary or evolved consciousness of the innumerable living forms involved in this extraordinary experiment. But, as we will see in the section on the psyche, only the most advanced organisms, lived in the last 50 million years, could have a nervous system perhaps capable of tuning forms of consciousness that could watch the world, going beyond the immediate instinctual needs, and even in this case we can not say whether these forms of perception could attain a conscious view of the complex scene of the living world.

The evolutionary process would then be endowed with a wholly unconscious creativity, at least until the first rudiments of consciousness appeared in the animal world, and in particular in humans. But since the conscious perception of the evolution of life by human beings is limited to a period that goes from just two centuries ago to today, we are led to wonder about the origin of human consciousness and its contents, and in particular about that complex and contradictory phenomenon that is the human psyche in its chronological evolution. The results of the scientific method, based on experimentation, are of the utmost importance and can not be disregarded, under penalty of returning to all those forms of naive and hazardous inflation of the psyche through which our consciousness has interpreted the world and the life from the beginning of human history. Scientific knowledge differs from any form of faith because it offers the tools to operate concretely and effectively on the reality of this world, modifying it according to the human intent: for example, from the genetic research comes genetic engineering, which allows to perform experiments which lead to a direct control over living organisms. The consequences of this power will reveal themselves in the future, but in any case it is an effective power made available to human will. At the same time, all those aspects of the evolutionary process that are still out of our scientific understanding, especially those concerning man, must be kept in mind: why an unconscious and aimless process should become a conscious, intelligent, self-reflexive and intentional experience?