We see the same pattern at Pompeii, Angkor, and Cahokia. Though contractions in the cities’ populations had different causes and effects, each was precipitated by the thorny problem of managing an enormous piece of human-built infrastructure in a constantly changing environment. Managing the humans themselves was an even bigger problem. Cities are concrete embodiments of human labor, and we can read the dissolution of their publics in the crumbling of walls, reservoirs, and plazas.
