Societal collapse (also known as civilizational collapse or systems collapse) is the fall of a complex human society characterized by the loss of cultural identity and of social complexity as an adaptive system, the downfall of government, and the rise of violence. Possible causes of a societal collapse include natural catastrophe, war, pestilence, famine, economic collapse, population decline or overshoot, mass migration, and sabotage by rival civilizations. A collapsed society may revert to a more primitive state, be absorbed into a stronger society, or completely disappear. Virtually all civilizations have suffered such a fate, regardless of their size or complexity, but some of them later revived and transformed, such as China, India, and Egypt. However, others never recovered, such as the Western and Eastern Roman Empires, the Maya civilization, and the Easter Island civilization. Societal collapse is generally abrupt.Anthropologists, (quantitative) historians, and sociologists have proposed a variety of explanations for the collapse of civilizations involving causative factors such as environmental change, depletion of resources, unsustainable complexity, invasion, disease, decay of social cohesion, rising inequality, long-term decline of cognitive abilities, loss of creativity, and misfortune. However, complete extinction of a culture is not inevitable, and in some cases, the new societies that arise from the ashes of the old one are evidently its offspring, despite a dramatic reduction in sophistication. Moreover, the influence of a collapsed society, such as the Western Roman Empire, may linger on long after its death.The study of societal collapse, collapsology, is a topic for specialists of history, anthropology, sociology, and political science. More recently, they are joined by experts in cliodynamics and study of complex systems. Source: Wikipedia (en)