The synthetic theory of evolution was created on the basis of the unification of ecology, genetics and Darwinism in the 1920s. Today it is considered the most holistic and fully developed. The synthetic theory of evolution embodied population genetics and classical Darwinism.
The first to introduce a genetic approach was Chetverikov, Sergey Sergeevich. In 1926, he published an article where the evolution of life (at a number of points) was examined from the point of view of genetics. In his work, Chetverikov deduced several points. As an example, he took natural populations of Drosophila. Thus, the scientist established:
- Mutations in nature occur constantly.
- Recessive changes can persist indefinitely in a heterozygous state.
- Over time (as they age), mutations accumulate in the form, while the signs of the species become shaky.
- The main factors of intraspecific differentiation are hereditary variation and isolation.
- Panmixia (free crossbreeding) leads to polymorphism, and selection leads to monomorphism of the species.
The theory presented by Chetverikov indicates that accumulation through random mutations contributes to an adaptively directed, regular flow during development. The development of the teachings was continued by such Russian geneticists as Romashov, Timofeev-Resovsky, Vavilov, Dubinin and others. The works of these and other figures formed the basis on which the synthetic theory of evolution is based.
In the 30 years of the work of Wright, Holdeims, Fisher laid the foundation for the development of teachings in the West.
One of the first works in which the synthetic theory of evolution was presented in its essence was Dobzhansky's monograph on the origin of species and genetics. The attention was focused on the study of the mechanisms of formation of the genetic system of populations in accordance with the influence of various factors. Factors, in particular, included hereditary variability, fluctuations in the number of individuals in different populations, and migration. The causes of evolution, as well as the reproductive isolation of new forms formed inside the species, had a great influence.
Outstanding is the contribution of Schmalhausen to the development of learning. In accordance with the creative union of embryology, evolutionary theory, paleontology, morphology, as well as genetics, the scientist conducted in-depth studies of the relationship between phylogenesis and ontogenesis, studied the main directions in evolution, and also developed several fundamental principles of modern teaching.
Among the fundamental studies , Huxley's work, Evolution. Modern Synthesis, occupies an important position. Of great importance were the studies of forms and rates of development undertaken by Simpson.
Synthetic theory is based on eleven main tenets. They were summarized by Vorontsov.
- Mutations, being small discrete changes in heredity, are considered evolutionary material that is random in nature.
- The main, to some extent, the only driving force for development is considered to be natural selection, which is based on the selection of small and random mutations.
- The smallest evolving unit is considered a population.
- Development has a gradual (gradual) and continuous character.
- The species includes many subordinate and at the same time distinguishable (morphologically, genetically, physiologically), but not reproductively isolated units.
- Evolution involves a divergence of attributes.
- The flow of genes (allele exchange) is allowed only within the species. In this regard, it (a species) is considered a holistic and genetically closed system.
- The properties of the species do not apply to forms that reproduce asexually and parthenogenetically.
- Macroevolution occurs through microevolution.
- The real taxon has a monophilic origin (refers to one ancestral species).
- Evolution is an unpredictable process ; it has a character that is not directed toward the ultimate goal.