Introduction
The lack of knowledge about the laws of heredity, the genetic and ecological structure of species, and the lack of experimental evidence of natural selection served as the basis for the growth of critical attitudes towards Darwinism. Few scientific theories spread as quickly as the theory of natural selection, immediately called Darwinism. Its success was mainly due to a broad synthesis of facts and concepts from various branches of biology, carried out by Darwin based on the hypothesis of natural selection. Evidence of the existence of the evolutionary process was obtained from reliable data from embryology, morphology, paleontology, and biogeography.
Embryological Evidence
The striking similarity of vertebrate embryos drew many researchers’ attention long before Charles Darwin. Domestic and foreign scientists have deeply studied the similarities of the initial stages of embryonic development of animals. In the process of ontogenesis, many features of the structure of ancestral forms are repeated: in the early stages – more distant ancestors, in the later stages – close ancestors (Quammen, 2004). All vertebrates have a chord at a particular development set, and many insects have a larval stage. Such similarity of embryonic stages is explained by the unity of origin of all living organisms. Some scientists independently formulated a biogenetic law that describes ontogenesis, that is, individual development, as a brief and concise repetition of phylogeny, the historical development of a species.
Morphological Evidence
Morphological evidence of evolution is based on the presence of homologous, rudimentary, and atavistic organs in many living organisms. Homologous organs have a similar structure plan, performing similar and different functions and developing from similar rudiments (Quammen, 2004). The study of the anatomy of mammalian limbs allowed people to establish a similar plan of structure and formation. Rudimentary organs have lost their meaning and function in phylogeny and remain in organisms in the form of underdeveloped appearances. Rudimentary bones at the site of the pelvic girdle in cetaceans and rudimentary hind limbs of a python indicate an origin from typical quadrupeds. The rudiments of a person are coccygeal vertebrae, the nictitating membrane, the remains of the hair covering the body, the appendix – the process of the cecum, and strongly developed ear muscles that allow them to move.
Paleontological Evidence
Paleontology points to the causes of evolutionary transformations. The richest paleontological material is one of the most convincing proofs of the evolutionary process that has been going on the planet for more than 3 billion years (Quammen, 2004). Finding and studying fossils of transitional forms makes it possible to compile paleontological evolutionary series of organisms. Fossil transitional forms are forms of organisms that combine features of older and younger groups. The findings and descriptions of such forms allow us to reconstruct the phylogeny of individual groups of animals. For example, ichthyostega is a fossil form linking fish with terrestrial vertebrates; an archaeopteryx is a transitional form from reptiles to Jurassic birds. The paleontological series is the sequel of fossil forms related to each other in evolution and reflect the phylogeny course.
Biogeographical Evidence
The peculiarities of the distribution of living beings on the planet are closely related to the transformation of the Earth’s crust and the evolutionary changes of species. This is indicated by the distribution of animals and plants on the surface of our planet, the comparison of flora and fauna of various continents, and islands, and the identification of relict plants and animals of different natural zones (Quammen, 2004). An example is Australia, where the formation of marsupials and cloacal mammals took place after separation from the rest of the continents. To understand the evolutionary process, flora and fauna of the islands, which turned out to be utterly dependent on the history of the origin of these islands, are of interest.
Anagenesis and Speciation
Anagenesis is a process of gradual changes that leads to the complication of the organization and improvement of existing forms of organisms. Anagenesis originates and is based on mutational variability and selection. In contrast to the population, at the species level of evolution, so-called systemic mutations come to the fore, i.e., changes affecting entire blocks of genes and causing severe changes in the body. Conversions of gene complexes that control the process of the formation of organs of an adult organism can be attributed to this category. One of these mutations in drosophila leads to the development of an additional pair of wings. Speciation is the process of species formation carried out due to the interaction of elementary evolutionary factors: mutations, gene drift, natural selection, waves of life, and isolation. The existence of anagenesis and speciation has not been fully proven, although it is possible to find scientific articles that hypothetically confirm their presence.
Natural Selection, Adaptation and Phylogeny
Natural selection is an evolutionary process in which individuals with traits conducive to survival reproduce faster. These favorable traits become more common among the population or species. Naturally selected features initially arise as a result of random genetic mutations. For selection to occur, there must be variability in the population, the trait controlling the variability must be heritable, and the trait’s variation must have an evolutionary advantage. Adaption is the development of any trait that contributes to the survival of a species and its reproduction. Phylogeny is the process of the historical development of wildlife and individual groups of its constituent organisms.
Genetic Drift
Genetic drift is the way in which evolution takes parts of genes and populations (Ward, 2018). The doctor demonstrates an example of genetic drift on a bowl of M&M’s candies, which are known to have different colors. That is, a person takes a handful of sweets by accident and sees that they are all the same color instead of being different. The same thing happens with genes, which is called genetic drift.
Opinion
I think Darwin did a lot of work and got a specific database and evidence that natural selection and evolution of species exist. Nevertheless, I am more inclined to believe that his theory is wrong, and I agree with some scientists in this opinion. The main achievement of Darwin, which has retained its significance to the present time, is the description of natural selection as a mechanism that ensures the fitness of organisms to the environment and their morphological diversity. Darwin believed that for differences to arise between two related forms, it is enough that forms with evasive signs are better adapted than forms with average values of signals.
The modern evolutionary theory considers selection a necessary but insufficient condition for the emergence of new species. For the evasive forms to give rise to new species, the exchange of genes between them must stop; that is, in one way or another, isolation conditions must develop that prevent crossing. Isolation can be any – evasive forms can reproduce in different places, at other times, on different forage plants — any restriction on the exchange of genes between states is suitable. If there is no such restriction, then a polymorphism is formed, or several different morphs within the same species. Darwin did not pay much attention to the problem of distinguishing species. He focused on the presence of transitional forms and varieties between species (Ward, 2018). Geographical races, or subspecies, represent local forms, quite definite and isolated. Still, since they do not differ significantly in noticeable or essential features, there is no other criterion than personal opinion to decide which of them to recognize as species and which as varieties.
Conclusion
In conclusion, Charles Darwin undoubtedly did an extensive study of various species and their origin. Nevertheless, the findings that the scientist made are still controversial and give other theories to substantiate evidence against the idea put forward by Darwin. Darwin’s genius was manifested in the fact that he explained speciation by the action of natural selection, still knowing very little about the mechanisms of heredity. The modern theory of natural selection, which allows us to find those parts of the genome on which natural selection acted and use this knowledge to create new plant varieties and animal breeds, preserves the Darwinian approach to explaining the fitness of organisms in the environment. Nevertheless, the knowledge and concepts that were developed after Darwin are more often used. In recent years, Darwin’s theory of evolution has been substantially corrected or supplemented. But its cornerstone – the concept of natural selection – has not gone away and still serves as the foundation for the entire edifice of modern biology.
References
Quammen, D. (2004). Was Darwin wrong? No. The evidence for evolution is overwhelming. National Geographic, 2(34), 1-13.
Ward, A. (2018-present). Evolutionary biology (DARWINISM) with John McCormack. [Audio podcast]. Web.