Demographic collapse

Societal collapse is the fall or disintegration of complex human societies. Societal collapse broadly includes abrupt societal failures such as that of the Maya Civilization, as well as more extended gradual declines of cultures, institutions, or a civilization like the fall of the Western Roman Empire. The general subject arises in anthropology, history, sociology, politics and other fields, and more recently in complex systems science.

Common factors that may contribute to societal collapse are economical, environmental, social and cultural, and disruptions in one domain sometimes cascade into others. In some cases a natural disaster (e.g. tsunami, earthquake, massive fire or climate change) may precipitate a collapse. Other factors such as a Malthusian catastrophe, overpopulation or resource depletion might be the proximate cause of collapse. Significant inequity may combine with lack of loyalty to established political institutions and result in an oppressed lower class rising up and seizing power from a smaller wealthy elite in a revolution. The diversity of forms that societies evolve corresponds to diversity in their failures. Jared Diamond suggests that societies have also collapsed through deforestation, loss of soil fertility, restrictions of trade and/or rising endemic violence.

The decline of the Roman Empire is one of the events traditionally marking the end of Classical Antiquity and the beginning of the European Middle Ages. Throughout the 5th century, the Empire's territories in western Europe and northwestern Africa, including Italy, fell to various invading or indigenous peoples in what is sometimes called the Barbarian invasions, although the eastern half still survived with borders essentially intact for another two centuries (until the Arab expansion). This view of the collapse of the Roman Empire is challenged, however, by modern historians who see Rome as merely transforming from the Western Empire into barbarian kingdoms as the Western Emperors delegated themselves out of existence, and the East transforming into the Byzantine Empire, which only fell in 1453 AD.

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