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 is, "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."
Johnson suggests, not unreasonably, that this explains why certain of the world's population groups, such as Native Americans and Australian Aborigines, have had disproportionately high levels of alcoholism: These groups never endured the cruel culling of the genetically unfortunate that town dwellers endured. If so, the high alcoholism rates among Native Americans are not, or at least not entirely, ascribable to the humiliations and deprivations of the reservation system. Rather, the explanation is that not enough of their ancestors lived in towns.
But that is a potential stew of racial or ethnic sensitivities that we need not stir in this correction of Investor's Business Daily. Suffice it to say that the good news is really good: Beer is a health food. And you do not need to buy it from those wan, unhealthy-looking people who, peering disapprovingly at you through rimless Trotsky-style spectacles, seem to run all the health food stores.
So let there be no more loose talk -- especially not now, with summer arriving -- about beer not being essential. Benjamin Franklin was, as usual, on to something when he said, "Beer is living proof that God loves us and wants us to be happy." Or, less judgmentally, and for secular people who favor a wall of separation between church and tavern, beer is evidence that nature wants us to be.