"The search for unpolluted drinking water is as old as civilization itself. As soon as there were mass human settlements, waterborne diseases like dysentery became a crucial population bottleneck. For much of human history, the solution to this chronic public-health issue was not purifying the water supply. The solution was to drink alcohol."
Often the most pure fluid available was alcohol -- in beer and, later, wine -- which has antibacterial properties. Sure, alcohol has its hazards, but as Johnson breezily observes, "Dying of cirrhosis of the liver in your forties was better than dying of dysentery in your twenties." Besides, alcohol, although it is a poison, and an addictive one, became, especially in beer, a driver of a species-strengthening selection process.
To avoid dangerous water, people had to drink large quantities of, say, beer. But to digest that beer, individuals needed a genetic advantage that not everyone had -- what Johnson describes as the body's ability to respond to the intake of alcohol by increasing the production of particular enzymes called alcohol dehydrogenases. This ability is controlled by certain genes on chromosome four in human DNA, genes not evenly distributed to everyone. Those who lacked this trait could not, as the saying goes, "hold their liquor." So, many died early and childless, either of alcohol's toxicity or from waterborne diseases.
The gene pools of human settlements became progressively dominated by the survivors -- by those genetically disposed to, well, drink beer. "Most of the world's population today," Johnson writes, "is made up of descendants of those early beer drinkers, and we have largely inherited their genetic tolerance for alcohol."
The health benefits of beer are frequently reported, and debated. However Johnson takes it a step further and ties the survival of civilization to the consumption of alcohol. The obvious jokes aside, this is an interesting and thought provoking postulation.
George Will's complete column is here. Johnson's book "The Ghost Map" can be found on Amazon.