Sometime around 7500 B.C., people began building clustered mud-brick houses at Catalhoyuk, Turkey. According to detailed archeological studies, for roughly the next thousand years, the same patterns of life persisted, apparently with all families living in the same fashion and with approximately the same level of goods and the same size houses. Analyses of the human remains show that men and women received the same level and type of food as well.
By around 6500 B.C., however, income and status inequality began to develop, and as it did, more violence also began to appear, including a significant number of individuals with healed head injuries, wounds that suggest to the archaeologists who have studied the site for more than forty years that such injuries were inflicted as a means of social control, but that such control was not necessary until pronounced income/resource inequality began to develop. This is, of course, a conclusion drawn by those studying Catalhoyuk, but it does appear without doubt that the society appeared more stable when the income levels were similar and that more violence occurred once income inequality began to develop.
I have to say that this scarcely surprises me. Historically, countries with high levels of income inequality have often had violent uprisings and/or revolutions, such as the French Revolution, the Russian Revolution, the Spanish Civil War, the Cuban revolution, the more recent violence in the Sudan, and the troubles in Colombia and Venezuela.
In looking at income inequality by country across the world, I was struck by several facts. First, among industrialized/technological nations, the United States has the greatest income inequality. Among all nations, there is a pronounced tendency for countries with high income inequality also to have high levels of societal violence, and that includes the United States.
All of which suggests that pushing for tax cuts on the wealthy and opposing increases in the minimum wage may well have costs beyond the merely monetary.