American sociologist Gerhard Lenski (1924-2015) From the mid-1960s until his death devoted himself to developing his macro-theoretical perspective, which he called "ecological-evolutionary theory." The first book in which this theory was presented was Power and Privilege (1966), then he further elaborated his position in the book Human Societies (1970) which has undergone many revised editions, to finally give a detailed account of his theory in the book Ecological-Evolutionary Theory (2006). Lenski attaches great importance to the genetic basis of human behavior. He believes that biological needs in all human societies are, in essence, always the same, and to meet those needs all societies create and maintain the same cultural subsystems: language, morality, ideology, kinship systems, technology, political organization, and religion.

In his opinion, population pressures were one of the strongest sources of human creativity and social change. Since the biological foundations of all societies are the same, differences in cultural patterns (in all the subsystems listed earlier), as well as the potential for social development, are a consequence of differences in the biophysical environment. In addition to the biophysical environment, most societies have a socio-cultural environment, that is, other societies and cultures. The socio-cultural environment acts in two ways: as a threat (military, political or economic), but also as a resource. The most important resources that surrounding societies give to society are technological and other innovations, which are obtained through cultural diffusion. Lenski believes that cultural diffusion has been a much greater source of useful information (in all cultural subsystems), than independent discoveries and inventions.

The most important cultural subsystem is technology, because technology is the meeting place of the biophysical environment and all other components of socio-cultural systems, and thus affects almost all aspects of human life. Technology, genetics, and the biophysical environment have a decisive influence on the choices made by individuals and societies. The need to save energy is the biggest motive and pressure for technological innovation. Although Lenski attaches the greatest importance to the study of all types of technology, he believes that ideology can have a reciprocal impact on the development of technology. During the evolution of societies, there was a change of periods in which ideology was prone to change, and thus technological change was happening, and periods in which ideology sought to keep society at the same technological levels, so there was resistance to new technologies. The ideological subsystem, in order to survive, strives to maintain the status quo and therefore opposes technological change. Technological stagnation is possible until economic pressures become large enough that the development of new technology becomes inevitable.

For Lenski, political economy is less important than ideology, which is viewed autonomously. Because technology is a key cultural subsystem for Lenski, he developed an evolutionary taxonomy of societies where the basis of distinction is the dominant technology in the economy. Thus, the types of societies that he singles out are: 1) hunting and gathering societies, 2) simple horticultural societies, 3) advanced horticultural societies, 4) simple agrarian societies, 5) advanced agrarian societies, 6) fishing societies, 7) maritime societies, 8) simple herding societies, 9) advanced herding societies, and 10) industrial societies.

These ten types of societies are not in direct evolutionary order. Hunting and gathering societies can adopt new technologies and become either fishing, horticultural, or livestock societies. These three types of society can be transformed into agrarian societies. Agrarian societies, in the technological sense, are characterized by the use of plows that pull draft animals, such as oxen or horses. Eventually, some agrarian societies grow into industrial societies by adopting new technologies. The speed of evolutionary change depends on many factors: the size of the population, the physical and social environment, as well as ideology. However, societies do not necessarily have to go through evolutionary development, because they can remain in a static state if there is no change in the physical and social environment, or they can fail if they do not adapt to changes in the environment.

With each transformation from one type of society to another with better technology, there comes a greater possibility for creating economic surpluses. Increasing the possibilities for creating these surpluses also enables stratification in society in terms of political power and social prestige. There is no hierarchy among hunter-gatherers in terms of political power, but only in terms of social prestige. The situation is similar with horticultural societies with a smaller population. But, as soon as large amounts of economic surpluses are created, there come population increases and higher population density, and that necessarily leads to the creation of stratification in society. Advanced horticultural and herding societies, in general, have three basic social classes: chiefs, lower chiefs, and ordinary people. Agrarian societies have the highest stratification and have a larger number of social classes. The ruling class in agrarian societies controls almost all the wealth of those societies, and the basis of economic exploitation can be agricultural rent, which is taken from subordinate classes, or exploitation can be done through the unpaid labor of slaves. The transformation of agrarian societies into industrial societies has led to a partial reduction in the hierarchical structure of societies.

Authors: Lenski, Gerhard. Jean, Lenski; Patrick Nolan.

Books: The Religious Factor: A Sociological Study of Religion's Impact on Politics, Economics, and Family Life (1961);

     -     Power and Privilege (1966); 

     -     Human Societies (1970);

     -     Ecological-Evolutionary Theory (2006).