Perhaps the oldest urbanized civilization, The city-state of Ur, known to man began its decline around 3000BCE in part due to rampant wealth inequality and internal rebellion...
Its important to note, this particular kind of internal conflict almost always leads to civilizational collapse.
"Texts uncovered from Lagash- one of the preeminent Summerian city states- indicate there was a massive chasm between the wealthy and the common people. Most of the latter being so mired in debt that they had to sell their own children to get our of debt."
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