Sociocultural evolution, sociocultural evolutionism or cultural evolution are theories of cultural and social evolution that describe how cultures and societies change over time. Whereas sociocultural development traces processes that tend to increase the complexity of a society or culture, thus decreasing efficiency, sociocultural evolution also considers process that can lead to decreases in complexity (degeneration) or that can produce variation or proliferation without any seemingly significant changes in complexity (cladogenesis). Sociocultural evolution is “the process by which structural reorganization is affected through time, eventually producing a form or structure which is qualitatively different from the ancestral form”. Most 19th-century and some 20th-century approaches to socioculture aimed to provide models for the evolution of humankind as a whole, arguing that different societies have reached different stages of social development. The most comprehensive attempt to develop a general theory of social evolution centering on the development of socio-cultural systems, the work of Talcott Parsons (1902-1979), operated on a scale which included a theory of world-history. Another attempt, on a less systematic scale, originated with the world-systems approach. More recent approaches focus on changes specific to individual societies and reject the idea of social progress, of an overall direction to change. Most archaeologists and cultural anthropologists work within the framework of modern theories of sociocultural evolution. Modern approaches to sociocultural evolution include neoevolutionism, sociobiology, modernization theory and the theory of postindustrial society. There have been many different societies throughout human history, with estimates as high as over one million; however, , only about two hundred or so different societies survive.