Basics of Evolution - Korzh O.P. - 2006

Part III. PATHS OF LIFE'S DEVELOPMENT

Chapter 17. Geochronology

17.2. Theories of the Origin of Life

Structure/149.html">The problem of THE ORIGIN OF life can arguably be considered the most enigmatic in all of natural science.

The proposed theories concerning the origin of life on planet Earth—at least most of them—draw upon the same factual material while emphasizing different aspects. One of the most contentious issues in this context is the confrontation between scientific and theological viewpoints.

To this day, the precise Definition of the term "life" itself remains unresolved, which stems from the endeavor to isolate The Essence of the living and identify the bearer of this essence. A clear confirmation of this is the ongoing debate over the status of Viruses: some scientists consider them living organisms, whereas others classify them as non-living organic entities.

Currently, the majority of scientists adhere to the view that there are no qualitative differences between living and non-living matter: all properties of living matter are, in one form or another, inherent to inanimate nature as well (evidently, the law of the transition of quantitative changes into qualitative ones is at play. Therefore, life is characterized today based on five axioms of theoretical biology:

1. A. Weismann's axiom: all Living organisms are the result of The Unity of the phenotype and the genotype, which provides the program for its construction and is inherited from generation to generation.

2. M.K. Koltsov's axiom: the genetic program is formed in a templated manner, utilizing the Gene of the preceding generation as the template for the GENES OF THE future generation.

3. Charles Darwin's first axiom: during transmission from generation to generation, genetic programs undergo random and undirected changes due to various factors, and only by chance may these changes prove advantageous under specific conditions.

4. N.V. Timofeeff-Ressovsky's axiom: random changes in genetic programs can be significantly amplified during the realization of the phenotype.

5. Charles Darwin's second axiom: the repeatedly amplified changes in genetic programs are subjected to Selection by environmental conditions.

The problems concerning the origin of life should be distinguished from its subsequent evolution. All theories on the origin of life are generally grouped into five major categories.

1. The steady-state theory (life has always existed).

According to this theory, Earth never originated anew but has always existed and was capable of sustaining life. Species similarly have always existed, with only two possibilities open to them: fluctuation in population size or extinction. This theory rejects the notion that the presence or absence of fossils can indicate the time of appearance or extinction of a particular species.

Thus, according to paleontological data, lobe-finned Fishes went extinct no less than 70 million years ago, yet in the 20th century, a representative of this group—Latimeria—was discovered near Madagascar. Proponents of this theory explain the unexpected discovery of any fossil in a given stratum not as the result of evolutionary development, but as a consequence of an increase in its population size or migration to locations favorable for the preservation of its remains. Most evidence supporting this theory is based on gaps in the paleontological record.

Views close to the aforementioned Concept of the eternity of life were also expressed by the domestic scientist V.I. Vernadsky. He believed that all living things originate exclusively from the living. From the very beginning, life represented a complex system capable of self-regulation. Therefore, the problem of The formation of life on Earth should actually be viewed as the problem of the Formation of the biosphere. Nevertheless, the scientist recognized the possibility of the subsequent evolutionary development of living matter.

2. Creationism (life arose As a result of a specific supernatural event in the past), which is upheld by adherents of religious teachings.

The process of the creation of the world by God is envisioned as having occurred only once and is consequently considered inaccessible to observation. For instance, Archbishop Ussher calculated in 1650 that God created the world in October 4004 BC and concluded this act with the creation of man on October 23 at 9:00 AM. Ussher obtained such precise dates by summing the lifespans of biblical figures from Adam to Christ. Understandably, such views contradict archaeological data, according to which Adam lived at a time when a well-developed urban civilization already existed in the Middle East. Attempts to resolve this contradiction are made by adjusting the duration of the "days" of creation: some believe the world was created in six literal 24-hour days and reject alternative views, whereas others interpret Genesis as a theological revelation. Given that its presentation is accessible to all people of all eras, the Bible should not be considered a scientific textbook; consequently, the information provided within it ought to be perceived philosophically. In the opinion of many theologians, the word "day" should be understood not as a 24-hour period, but as a certain epoch during which extraordinary events transpired.

Specifically, the Bible portrays the creation of the world in several sequentially ordered stages:

1) the beginning;

2) the creation of the planet, which was in darkness and surrounded by gases and Water vapor;

3) the penetration of light through the clouds;

4) the formation of the atmosphere; “

5) The Emergence of continents;

6) the appearance of plants;

7) the purification of the atmosphere and the formation of seasons;

8) the emergence of marine animals and early birds;

9) the evolution of mammals;

10) the appearance of humans.

The question of how the chronological sequence of events in the Book of Genesis is rendered more or less accurately remains open.

Theology comprehends truth through Divine revelation and faith. Science deals exclusively with phenomena that are substantiated by facts; therefore, it will never be able to either prove or disprove these concepts.

3. Spontaneous generation (life constantly arises from non-living matter).

This theory was widespread in ancient China, Babylon, and Egypt, serving as an alternative to creationism, alongside which it coexisted for a certain period. Aristotle not only adhered to this theory but also developed it, arranging all organisms into a scale of nature. According to Aristotle, certain particles of matter

contain an active principle that, under appropriate conditions, gives rise to living organisms. Species of living organisms are in no way interconnected; each arises spontaneously and develops independently of others. At the same time, evolutionary advanced species emerged long ago and had ample time to reach high evolutionary rungs, whereas primitive forms (primarily Bacteria) have just appeared and are only at the initial stage of their development. Following the spread of Christianity, this theory receded into the Background, although it still had proponents as late as the 17th century. For instance, Jan Baptista van Helmont (1577–1644) 'created' mice in three weeks using a dark closet, a dirty shirt, and a handful of wheat. However, subsequent experiments (Redi, Leeuwenhoek, Spallanzani) called The Theory of spontaneous generation into question. It was definitively refuted by Louis Pasteur, who experimentally proved the validity of biogenesis (life can arise only from pre-existing life). In the latter case, a new question arises: where did the first Organism come from?

4. The panspermia theory (life was brought to our planet from outside).

This theory proposes no mechanism to explain the initial emergence of life, shifting the very problem of its origin elsewhere—beyond Earth. According to this hypothesis, life could have originated multiple times at different times in various PARTS OF THE Universe. One confirmation of this theory is the recent discovery of Organic compounds on meteorites and comets. These very substances are considered the 'seeds' from which life on Earth evolved. There are other, more extravagant hypotheses within this group.

According to Hoyle and Wickramasinghe, cosmic dust is a mixture of Cellulose, other organic polymers, and even microorganisms. During the formation of new stars, most microorganisms perish due to unsuitable conditions, but viable microorganisms can be brought to planets along with meteorites and comets. It has been experimentally confirmed that spores of certain bacteria can survive in interstellar space for up to 45 million years, which is deemed sufficient to reach new planets.

According to V.I. Goldanskii's hypothesis, at temperatures close to absolute zero, the Arrhenius rule ceases to work, and under METABOLISM/18.html">The Influence of ultraviolet radiation in outer space, Biopolymers are formed, including complex molecules such as Proteins. It has been calculated that as Earth passes through a cosmic dust cloud over the course of 1–10 million years, 10–100 billion tons of organic matter could settle on its surface (figures that exceed the volume of our planet's modern biomass). The Second Stage of life's development was The breakdown of mirror Symmetry and the formation of a chirally pure environment (left-handed Amino Acids and right-handed sugars). The Third Stage was the formation of polynucleotides, which creates the preconditions for self-Replication and the subsequent maintenance of chiral purity.

Perhaps the most intriguing variant in this group is the theory of alien intervention. Life on Earth (and possibly the planet itself) was created by beings far more advanced than us, who constantly monitor Evolutionary Processes and periodically intervene in the general course of history (in this context, the Bible is suggested to be viewed as a chronicle of human communication with extraterrestrials).

5. Biochemical evolution — life arose as a result of processes governed by Physical and Chemical laws.

According to A.I. Oparin's theory (1923), the atmosphere of primordial Earth was reducing rather than oxidizing like today's. Under such conditions, organic compounds could form from simpler substances driven by intense solar radiation (primarily the ultraviolet spectrum) due to the absence of an ozone layer at the time. The gradual accumulation of organic matter in the ocean ultimately contributed to the formation of the primordial soup, from which life gradually emerged. It was later proven experimentally that organic matter is synthesized much more easily in a reducing environment than in the presence of oxygen. The possibility of obtaining amino acids and other low-molecular-weight organic compounds from inorganic elements with their subsequent polymerization was also confirmed. The next stage in The Development of life is considered to be the combination of NUCLEOTIDES' self-replication capacity with the catalytic activity of Polypeptides, which, following the formation of the primary Cell membrane, led to the appearance of the simplest organism feeding on the primordial soup.

The weak point of this theory is the necessity of a high concentration of organic matter in the primordial body of water for the emergence of coacervates or other prebiological formations. Several factors could counteract the formation of such a soup: solar radiation not only contributed to the creation of organic substances but also to their degradation; organics could be filtered into groundwater, settle in silt, and be washed ashore.

Subsequently, a hypothesis was put forward regarding the decisive role of fine clay particles in the origin of life. Clay is a finely dispersed fraction of sedimentary rocks, on the individual particles of which complex organomineral complexes arise. The specific structure of these complexes dictates the corresponding adsorption of amino acids and Lipids by clay particles. Thus, a primitive code emerges, which governs the abiotic synthesis of polypeptides and gives rise to prebiological systems.

It later turned out that clays are completely unsuited for this role, as they predominantly concentrate water and ionic components. Therefore, preference as biochemical adsorbents and catalysts is given today to alkali feldspars, which, due to weathering, possess a microporous surface and were quite abundant on Earth's surface more than 3.5 billion years ago (Fig. 17.1). The pores of feldspars could trap organic substances and transform into catalytic microreactors, protected from ultraviolet radiation and other negative influences, thereby facilitating the concentration of organics and the progression of prebiological evolution. However, the actual transition from a coacervate drop (or other prebiological formations) to the simplest organism remains the least thoroughly elaborated.

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Fig. 17.1. A cast of a network of tubes etched into The surface of an alkali feldspar. It is believed that life could have originated precisely within these structures (after I. Parsons, R. Martin, J. Smith, cited in Ya.M. Danko, 2001)