there's a fire
If the rich weren't rich, the poor would have no one to long to be like.
If the prosperous weren't as prosperous, the famished would have no level of nourishment to aspire to.
If Rembrandts weren't as beautiful, high school students wouldn't hate what they drew.
Aborigines aren't sad people.
Aborigines with TVs are.
Why? Because the aborigines with TVs are sold a life better than their own. They are told, what they have isnt good enough. Maybe no one comes out and says "Oh look how much better they are then you", its not that they are being told they are better, its the awareness that there is something better out there that makes them want it.
A baby won't want a lollipop when it's hidden in your backpocket
A baby will want a lollipop when it's held just outside of his reach.
Humans aren't sad people
Humans with civilization are.
Civilizations lead to an existince outside of simply who is in the hut next to you. It led to colonies, and states, and empires. This larger existince lead to a larger awareness. Even Mesapotomia had its ghettos, maybe not in the strictly ethnic sense as the word is used now, but in the schismatic way. There were rich, and there were poor. The poor finally knew the rich existed, and wanted what the rich had.
And we've been trying to figure out how to even up the game ever since.