Until it doesn't - how many draft horses do you see working now? Besides which, we've got over fifty years of history telling us that wealth concentration is happening faster and faster. If just that trend alone continues then within our lifetime most people would not be earning enough to sustain themselves.

We're such a small segment of history, though. We're just a blip on the timeline of the universe. Look at how our population has expanded in the last 100 years alone...some things are just unsustainable.