Biological progress is the only direction of evolution that led to the emergence of man. This direction determines the transition in the process of evolution to the social level.
As you know, the ways of achieving biological progress, the course of historical development (phylogenesis) for each particular taxon (group) depends on the adaptive zone in which this taxon actually evolves. Equally important are the possibilities of restructuring in the organizational structure of the group.
Touching upon the main problem that biological progress solves, scientists pay attention to the role of each available factor in determining one direction or another in development. In other words, studying this particular issue allows you to see how fitness can be enhanced and evolution as a whole can occur.
The first to study this area was J. B. Lamarck. The scientist has divided biological progress into two types. He attributed gradation to the first - raising the organizational level. The second of them, according to the scientist, is the formation of a variety of types of organization at each specific level. The scientist believed that these two processes are independent of each other. Thus, gradation is due to an internal desire for improvement, while diversity is formed under the influence of the environment. It should be noted that, despite the fact that J. B. Lamarck misinterpreted the mechanism of two directions, their very existence is an objective fact.
Darwin viewed biological progress differently. He equalized the concepts of evolution and adaptation. As a result of this, according to Ch. Darwin, an increase in the organizational level was only a partial result of this whole process. As a rule, an increase in fitness is combined with the complexity of the organization in the process of evolution. In the process of divergence of signs (divergence), a constant complication of the biotic environment occurs. Darwin further suggested that adaptation to a more complex environment can be achieved only through a more complex body structure. Subsequently, biological progress was studied in two directions. The studies were conducted in Russia by A. Severtsov and abroad by J. Huxley and B. Rensch.
Like J. B. Lamarck, B. Rensch believed that the development of evolution is possible not only vertically, but also horizontally. The formation of diversity at one level of organization was called Rensch cladogenesis, and the exit to a new level - anagenesis. In turn, J. Huxley returned to the definition of "city" (stage), proposed by J. B. Lamarck. At the same time, the scientist singled out the third direction along which biological progress occurs, calling it stasigenesis. He considered this direction a stabilization phenomenon, preservation of persistent, unchanging branches. Analyzing all directions, J. Huxley came to the question of where evolutionary development can lead in general and what can become a criterion for its progressiveness. As a result, the Huxley paradox arose: who is more progressive - the tuberculous bacillus that provokes the disease of a person, or the person himself?
The scientist tried to solve the questions that appeared in his theory of unlimited and limited development. According to this theory, evolution is certainly biological progress. However, this development is a group, and therefore limited. Passing from one step to another, each taxon (group) progresses, but, along with this, comes to extinction, that is, to stasigenesis. Moreover, only one direction of development that led to the appearance of man is unlimited. This is mainly due to reaching a completely new evolutionary level - the social one.