we've had hundreds of thousands of years and we don't seem even remotely equalized
Because various governments keep interfering with the free market. Interference in the market is what keeps equilibrium from being reached. Do note that I'm talking about economic equilibrium, which is almost certainly not the same as "equality" in whatever way you're thinking of.
Explain this. Why can't we imply that both China and America should treat their workers better?
Well, the phrase we should be using is "standard of living." Right now, the labor market is not at equilibrium. Our wages are artificially high and the wages of the Chinese are artificially low. If you were to raise the minimum wage in China, it would have to be paid for somehow. In the immediate term, this would mean massive unemployment for the marginal Chinese workers. In the longer term, it would most certainly have to mean falling wages in the developed world.
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SmartMuffin - Because anything less would be uncivilized - http://img.imgcake.com/smartmuffin/barkleyjpgde.jpg
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