The idea of ??a gradual and continuous change in all species of plants and animals was expressed by many scientists long before Darwin. Therefore, the very concept of evolution is a process of long, gradual, slow changes that ultimately lead to radical, qualitative changes – the emergence of new organisms, structures, forms and species, penetrated into science as early as the end of the 18th century.
However, it was Darwin who put forward a completely new hypothesis regarding living nature, generalising individual evolutionary ideas into one, the so-called theory of evolution , which was the most widely spread in the world.
During the voyage around the world, Charles Darwin collected the richest material that indicated the variability of plant and animal species. A particularly striking finding was the huge skeleton of a fossil sloth discovered in South America. Comparison with modern, small in size sloths, prompted Darwin to think about the evolution of species.
The richest empirical material accumulated by that time in geography, archeology, paleontology, physiology, taxonomy, etc., allowed Darwin to draw a conclusion about the long evolution of wildlife. Darwin expounded his concept in his work “The Origin of Species by Natural Selection ” (1859). The book of Charles Darwin had a phenomenal success, its first circulation (1,250 copies) was sold on the first day. The book dealt with explaining the emergence of living beings without appeal to the idea of ??God.
It should be noted that despite the huge popularity among the reading public, the idea of ??a gradual appearance in the living nature of new species for the scientific community of the time turned out to be so unusual that it was not accepted immediately.
Darwin suggested that in animal populations there is competition, thanks to which only those individuals survive that have properties that are beneficial under given specific conditions, allowing to leave offspring. Darwin’s evolutionary theory is based on three principles: a) heredity and variability; b) the struggle for existence; c) natural selection. Variability is an inalienable property of all living things. Despite the similarity of living organisms of the same species, two completely identical individuals can not be found within the population. This variation of features and properties creates the advantage of some organisms over others.
Under normal conditions, the difference in properties remains invisible and does not have a significant effect on the development of organisms, however, under changing conditions, especially in the unfavorable direction, even the smallest difference can give one organisms a significant advantage over others. Only individuals with the appropriate conditions of the properties are able to survive and leave offspring. Darwin distinguishes between uncertain and definite variability.
A certain variability , or adaptive modification, is the ability of individuals of one species to react in an identical way to changes in the environment. Such group changes are not inherited, so they can not supply material for evolution.
Uncertain variability , or mutation , – individual changes in the body, transmitted by inheritance. Mutations are not directly related to changes in environmental conditions, but it is precisely indeterminate variability that plays a crucial role in the evolutionary process. Accidentally appeared positive changes are inherited. As a result, only a small part of the offspring survive and reach maturity, possessing useful hereditary properties.
Between living beings, as Darwin believes, the struggle for existence unfolds. Specifying this concept, Darwin pointed out that more species are born inside the species than live to an adult state.
Natural selection is the leading factor in evolution, explaining the mechanism of the formation of new species. It is this selection that acts as the driving force of evolution. The mechanism of selection leads to selective destruction of those individuals that are less adapted to environmental conditions