Early in human history there were probably few alcoholics or addicts, because the alcohol content available in fermented fruit was low, and plants that produced other intoxicating substances were relatively scarce.  The development of agriculture created food surpluses, especially of grain, the major ingredient in beer, and a class of workers that was not tied to food production.  These specialized occupations — brewing and raising non-food crops among them — allowed a gradual increase in the organized  production of mood-altering substances.

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