New theory on the collapse of Teotihuacan in the 8th century AD

[Dave Beatty]

New theory on what caused the collapse of Teotihuacan (city-state in Mexico that was home to 125,000+ people) in the 8th century - civil war.

http://phys.org/news/2015-03-anthropologist-explanation-collapse-ancient-city.html

A very similar theory exists for the collapse of Cahokia in the 13th century (see Emerson's Cahokia and the Archaeology of Power etc).