Fundamentals of Evolution - O.P. Korzh - 2006

Part I. MICROEVOLUTION

Chapter 1. History of the Development of the Synthetic Theory of Evolution

Following the publication of Charles Darwin's seminal work, On THE ORIGIN OF Species, the idea of evolution was accepted by almost all scientists, yet scientific debates flared up around the recognition of natural Selection as the driving force of evolution. Many were troubled by the question: how are the favorable traits of individuals that survived through selection preserved in their descendants without blending away among other expressions of the same trait during crossing? This problem worried Darwin himself; shortly after the release of his book, "Fleeming Jenkin's nightmare" became a stumbling block. Being a mathematician, F. Jenkin mathematically and mechanistically proved that when crossing carriers of certain traits with individuals lacking such traits, a gradual dilution of the trait from generation to generation must be observed, thereby rendering the operation of natural selection impossible. Only genetics, which studies the patterns of heredity and Variability in organisms, was able to provide an answer to this. However, the early geneticists questioned not only Darwin's views on the mechanisms of heredity, but the very idea of natural selection.

The second issue was clarifying the ability of natural selection—which seemingly performs merely the function of a sieve—to ensure the gradual Nature of the evolutionary process. According to S.S. Schwartz, fundamental debates regarding The Theory of natural selection even today boil down to the question: is selection the creator or the editor of evolutionary transformations? The formulation of the Synthetic Theory of evolution—a synthesis primarily of classical Darwinism and genetics—helped to smooth out the sharpness of this problem in its time.

Today, a significant number of evolutionary theories exist. Ernst Mayr proposed their universally accepted Classification, according to which evolutionary theories are divided into:

A. Monistic theories (relying on the action of a single factor).

1. Exogenous (direct determination by the environment):

a) random changes (action of radiation, etc.);

b) adaptive changes.

2. Endogenous (determined by internal causes):

a) goal-directed (orthogenesis);

b) volitional (true Lamarckism);

c) mutational constraints;

d) epigenetic constraints.

3. Random spontaneous Mutations.

4. Natural selection.

B. Synthetic theories (relying on the action of multiple factors).

1. Most Lamarckian theories (1b + 2a + 2b).

2. Some modern Lamarckian theories (1b + 2b + 2c + 4).

3. Initial stage of The formation of the synthetic theory of evolution (3 + 4).

4. Formulated synthetic theory of evolution (1a + 2c + 2d + 3 + 4).

However, according to K.M. Zavadsky, this classification requires certain clarifications, primarily concerning the teachings of C. Darwin. Firstly, it does not belong to monistic (or monofactorial) theories, as it presupposes several Prerequisites for the evolutionary process. Secondly, the given classification pays no attention to the Struggle for Existence, which Darwin considered one of the most important prerequisites of the evolutionary process. Certain other evolutionary theories can also be considered synthetic.

The works of G. Hardy and W. Weinberg mathematically substantiated The ratio of homo- and heterozygotes in populations. The Hardy-Weinberg law ((p + g)²= p² + 2pg + g²) demonstrates that heredity itself does not lead to changes in allele and genotype frequencies for specific traits. It accounts for any long-term Maintenance of the concentration of two alleles of a single Gene within a population, provided that the following conditions are met:

1) the population must be infinitely large;

2) absolute panmixia is maintained (unrestricted mating options);

3) the mutation process is absent;

4) the selective value of alleles must be equal;

5) overlap of generations must not be observed.

If these conditions are not met, even in the case of equal selective value of two alleles, one of them may be driven out of the population. This phenomenon is known as Genetic Drift.

One of the most crucial roles in shaping the modern synthetic theory of evolution was played by the works of S.S. Chetverikov, who proved that:

1) the mutation process occurs in natural populations;

2) most arising mutations reduce the viability of their hosts, although an increase is occasionally observed;

3) under conditions of free mating, a species remains sufficiently stable, As a result of which, According to the Hardy-Weinberg law, the ratio of allele frequencies can remain unchanged indefinitely;

4) most individuals of each species are characterized by heterozygosity for various alleles;

5) due to species "Aging," mutations accumulate within it that "disrupt" the original traits;

6) genetic variability reaches its greatest development when isolated colonies are formed.

Thus, it was proven that uniformity may apply only to phenotypic traits, whereas the genotype almost always turns out to be heterozygous and laden with numerous mutations. It was this scientist who discovered the phenomenon known as population waves, or waves of life.

Theoretical Population Genetics was pioneered by the classical works of R. Fisher and S. Wright. They mathematically proved The impact of selection on inherited traits.

Y.A. Filipchenko proposed dividing evolutionary doctrine into microevolution (speciation processes) and macroevolution (formation of supraspecific taxa). This was done to emphasize the different origins and evolutionary Pathways of the species and supraspecific levels. In the modern sense, these terms began to be used by T.G. Dobzhansky and N.W. Timoféeff-Ressovsky. The former formulated METABOLISM/2.html">THE CONCEPT OF The system of isolating mechanisms of evolution, while the latter proposed terms such as elementary evolutionary material, elementary evolutionary phenomenon, elementary evolutionary unit, and elementary evolutionary factors. Mention should also be made of I.I. Schmalhausen, whose works elucidated a significant number of evolutionary issues (stabilizing selection, development of ontogeny, cybernetic issues in biology, etc.). Naturally, There are many more scientists who contributed to The Development of the synthetic theory of evolution, and THE CONTRIBUTION OF each could be discussed separately.

Thus, in the 1940s, the core tenets of the synthetic theory of evolution were formulated.

The theory received its name thanks to Julian Huxley's book Evolution: The Modern Synthesis, first published in 1942. The synthetic theory remains the leading evolutionary framework to this day, but in the view of many evolutionary biologists, the time is ripe for a new synthesis that would combine all the strengths of the previous theory with recent findings from various scientific disciplines.

Food for Thought

Throughout human history, so many hypotheses regarding the fundamental patterns of living Organism evolution have emerged that today, perhaps, virtually no unaddressed gaps remain. At the same time, problems in modern evolutionary theory have not diminished—on the contrary, their number grows steadily with each passing day. This concerns not only minor details but also the core principles of the synthetic theory of evolution. One may hope that new discoveries, even minor ones, will compel us to revise our views on the Causes and Mechanisms of the evolution of living matter.