[SunkenCiv]

Detroit started to bleed in the 1960s, after the late 1950s auto industry peak (first 10 million vehicle year, and the last one for a long while), followed by the riots, white flight, and the disaster that was Coleman Young.

Cahokia got flooded out, and the flood killed the crops in the field. It never recovered.

[Bernard Marx]

Yes, I read -- and understood -- the original Cahokia article. And I researched Detroit's decline out of strict habit.

Maybe my point was a bit too abstract. Humans don't learn from past natural disasters (witness Fukushima where ancient stone monuments on the hillsides warn not to build below their elevation because of tsunami danger.)

Neither do they learn from past political and cultural folly. Detroit is just one example out of of hundreds in which human greed/vanity/stupidity/whatever have led to severe decline and often destruction. Neither do cultures as a whole learn much from the past. Right now I'm getting a strong sense of 1930s deja vu all over again.