Evolutionary theories are based on the assumption that societies gradually change from simple beginnings into even more complex forms. Early sociologists beginning with Auguste Comte believed that human societies evolve in a unilinear way- that is in one line of development. According to them social change meant progress toward something better.They saw change as positive and beneficial. To them the evolutionary process implied that societies would necessarily reach new and higher levels of civilization.L.H Morgan believed that there were three basic stages in the process: savagery, barbarism and civilization.Auguste Comte's ideas relating to the three stages in the development of human thought and also of society namely-the theological, the metaphysical and the positive in a way represent the three basic stages of social change. This evolutionary view of social change was highly influenced by Charles Darwin's theory of Organic Evolution.
Those who were fascinated by this theory applied it to the human society and argued that societies must have evolved from the simple and primitive to that of too complex and advanced such as the western society. Herbert Spencer a British sociologist carried this analogy to its extremity. He argued that society itself is an organism. He even applied Darwin's principle of the survival of the fittest to human societies. He said that society has been gradually progressing towards a better state. He argued that it has evolved from military society to the industrial society. He claimed that western races, classes or societies had survived and evolved because they were better adapted to face the conditions of life. This view known as social Darwinism got widespread popularity in the late 19th century. It survived even during the first phase of the 20th century. Emile Durkheim identified the cause of societal evolution as a society's increasing moral density.Durkheim viewed societies as changing in the direction of greater differentiation, interdependence and formal control under the pressure of increasing moral density. He advocated that societies have evolved from a relatively undifferentiated social structure with minimum of division of labor and with a kind of solidarity called mechanical solidarity to a more differentiated social structure with maximum division of labor giving rise to a kind of solidarity called organic solidarity.
Cyclical theories of social change focus on the rise and fall of civilizations attempting to discover and account for these patterns of growth and decay.Spengler, Toynbee and Sorokin can be regarded as the champions of this theory.Spengler pointed out that the fate of civilizations was a matter of destiny. Each civilization is like a biological organism and has a similar life-cycle, birth, maturity, old-age and death. After making a study of eight major civilizations including the west he said that the modern western society is in the last stage i.e. old age. He concluded that the western societies were entering a period of decay as evidenced by wars, conflicts and social breakdown that heralded their doom.
Arnold Toynbee's famous book 'A study of History' (1946) focus on the key concepts of challenge and response. Every society faces challenges at first, challenges posed by the environment and later challenges from internal and external enemies. The nature of responses determines the society's fate. The achievements of a civilization consist of its successful responses to the challenges; if cannot mount an effective response it dies. He does not believe that all civilizations will inevitably decay. He has pointed out that history is a series of cycles of decay and growth. But each new civilization is able to learn from the mistakes and to borrow from cultures of others. It is therefore possible for each new cycle to offer higher level of achievement.
Pitirin Sorokin in his book Social and Culture Dynamics - 1938 has offered another explanation of social change. Instead of viewing civilization into the terms of development and decline he proposed that they alternate of fluctuate between two cultural extremes: the sensate and the ideational. The sensate culture stresses those things which can be perceived directly by the senses. It is practical, hedonistic, sensual and materialistic. Ideational culture emphasizes those things which can be perceived only by the mind. It is abstract, religious concerned with faith and ultimate truth. It is the opposite of the sensate culture. Both represent pure types of culture. Hence no society ever fully conforms to either type. As the culture of a society develops towards one pure type, it is countered by the opposing cultural force. Cultural development is then reversed moving towards the opposite type of culture. Too much emphasis on one type of culture leads to a reaction towards the other. Societies contain both these impulses in varying degrees and the tension between them creates long-term instability. Between these types lies a third type 'idealistic' culture. This is a desirable blend of other two but no society ever seems to have achieved it as a stable condition.
Functionalist or Dynamic theories:
In the middle decades of the 20th century a number of American sociologists shifted their attention from social dynamics to social static or from social change to social stability.Talcott Parsons stressed the importance of cultural patterns in controlling the stability of a society. According to him society has the ability to absorb disruptive forces while maintaining overall stability. Change is not as something that disturbs the social equilibrium but as something that alters the state of equilibrium so that a qualitatively new equilibrium results. He has stated that changes may arise from two sources. They may come from outside the society through contact with other societies. They may also come from inside the society through adjustment that must be made to resolve strains within the system. Parsons speaks of two processes that are at work in social change. In simple societies institutions are undifferentiated that is a single institution serves many functions. The family performs reproductive, educational, socializing, economic, recreational and other functions. A process of differentiation takes place when the society becomes more and more complex. Different institutions such as school, factory may take over some of the functions of a family. The new institutions must be linked together in a proper way by the process of integration. New norms must be established in order to govern the relationship between the school and the home. Further bridging institutions such as law courts must resolve conflicts between other components in the system.