"The economy has absorbed automation before; agricultural employment collapsed from ninety percent of the American workforce to two percent and civilization continued."
This automation happened between around 1910 and 1930. With WWI, the great depression, WWII, Communist Russia, failure of the gold standard, etc., some argue that is when civilization died.
"some argue that is when civilization died."
Its more that that's when per-industrialized civilization died. Or more specifically when the old medieval, agrarian aristocracies last trace of wealth and power died. At least in the new world they did...they still seem to have some influence in Europe which to Americans is really weird but I guess its to be expected.