Sociocultural evolution is a part of the evolution of life, a process that has been best formulated in Darwinian terms. Although some discussions differentiate biological and social evolution, in fact, the individual and the social setting are necessarily complementary parts of a single process. Human life is generated in the biology of individuals, but it survives and reproduces by virtue of the aggregate activities and interactions that take place as a part of societies. Whereas all living forms are in some way complex, social complexity is best understood as the compounding of successive levels of integration, of which the individual is one. Thus, no matter the complexity of a human cell, an individual, a family, a band, or a nation, this complexity is compounded by requiring additional interrelationships—and hence organization—among the aggregated components, thereby creating new levels of integration.
Human society grows by increasing energy flow. This is done first by biological expansion of the population. Natural selection has favored those that organized in order to reproduce, thus creating societies—what Spencer called the superorganism. It is the evolution of human superorganisms that we call social or cultural evolution. The Darwinian processes of reproduction, variation, and natural selection concern individuals, but societies exist to propagate individuals and continue to survive while individuals die. Human society is a facet of natural selection in that it organizes people to reproduce the human species.
To a degree unmatched by other species, human beings control a vast range of extrasomatic energy forms that are captured, gathered, cultivated, and mined from the environment and other societies. This extraction of energy is a cost to the environment caused by the emergence and evolution of human society. It may also be seen as a coevolution in which the human component differentially promotes and inhibits the evolution of many other species. Culture consists of the mental models people make to deal with the external world, and the behavioral and material forms that correspond to these representations. People use these mental models to manipulate the external world, to control external energy forms. In actual historical fact, the models may be the basis for creating controls, or the model may be created to describe a control that has been discovered to work; in any event, the external controls and their models develop in an interactive process. Mental models trigger energy flows. When we speak of the evolution of culture, we are speaking of both the change in the mental models and the changes in energy forms that correspond to these models. Given that both are involved, the term ‘‘cultural evolution’’ has been used to refer to two phases of changing human behavior: (1) the process whereby human beings adapt their mental models and social and cultural behavior to deal with challenges to their survival, and (2) the process whereby mental models, societies, and cultures become more complex as they adapt to deal with challenges to their survival.
Some treatments of cultural evolution see the first as adaptation and prefer to see the increasing complexity in terms of more complicated or compounded social organizations, or in more complicated technology that allows for the control of greater sequences of energy. The relationship between energy and cultural evolution lies in two phases of the process. One is the construction of ever longer and more complex linked trigger-flow systems. The other is the harnessing of additional energy from the environment, allowing more opportunities to tap the flow through its successive stages of dissipation. The Australian aborigines set savanna fires that release an immense amount of energy but exercise no further control over it. There is no successive system of triggers. In contrast, the fire in a steam locomotive converts water to steam that pushes a piston, that directly turns the wheels, that travels along tracks and pulls a number of railway cars, etc. The detonation of a nuclear bomb requires the careful arrangement of a chain of trigger actions before the explosion emerges.