

We are by no means the most bibulous people: according to the World Health Organization, 39 other nations outdrink us, a list topped by Luxembourg, where residents manage to ingest roughly 284 bottles of beer and 88 bottles of wine annually, no doubt to salve the indignation of explaining that their country isn’t part of Belgium.

Yet even though we Americans drink less than some others, we can hold our own, especially now that the peak ethanol season is under way. Liquor sales in December, according to hospitality trade groups, are usually a good 50 percent higher than in other months, and that’s hardly a surprise. December is a time of multicreedal spirituality and festivities, and alcohol has been a fixture of celebration and religious ritual since humans first learned to play and pray. December is also cold, dark and miserable, a meteorological migraine begging for home remediation, and alcohol is perhaps humanity’s oldest medicine.

Moreover, December is a time for family, and a taste for alcohol, it seems, is all in the family, the extended phylogenetic family of primates and other animals that make fruit a centerpiece of their diet. Nothing broadcasts the presence of ripe, digestible fruit as effectively as the aroma of fermentation. We’re frugivores at our core.

“As far back as we can look, humans have had a love affair with fermented beverages,” said Patrick McGovern, an archaeological chemist at the University of Pennsylvania. “And it’s not just humans. From fruit flies to elephants, if you give them a source of alcohol and sugar, they love it.”

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Humans may have an added reason to be drawn to alcohol. Throughout antiquity, available water was likely to be polluted with cholera and other dangerous microbes, and the tavern may well have been the safest watering hole in town. Not only is alcohol a mild antiseptic, but the process of brewing alcoholic beverages often requires that the liquid be boiled or subjected to similarly sterilizing treatments. “It’s possible that people who drank fermented beverages tended to live longer and reproduce more” than did their teetotaling peers, Dr. McGovern said, “which may partly explain why people have a proclivity to drink alcohol.”

Credit Serge Bloch

Dr. McGovern and other archaeologists have unearthed extensive evidence of the antiquity and ubiquity of alcoholic beverages. One of the oldest known recipes, inscribed on a Sumerian clay tablet that dates back nearly 4,000 years, is for beer. Chemical traces inside 9,000-year-old pottery from northern China indicate that the citizens of Jiahu made a wine from rice, grapes, hawthorn and honey, a varietal recently brought back to life by the intrepid palates at Dogfish Head brewery in Delaware. Last month, Dr. McGovern, John S. Henderson of Cornell University and colleagues reported evidence in The Proceedings of the National Academy of Sciences that the earliest known chocolate drink, made from the cacao plant in Honduras 1,400 years ago, was probably a fermented beverage, with an alcohol content similar to beer, a discovery that brings to mind the classic Onion T-shirt: “I’m like a chocoholic but for booze.”

Researchers caution, however, that if we humans are congenitally inclined to drink, we are designed to do so only in moderation. We are not, in other words, Syrian hamsters, the popular pet rodents that also are a favorite of alcohol researchers. Syrian hamsters are the Andy Capp of the animal kingdom. “They’ll drink alcohol whenever offered the option,” said Howard B. Moss, associate director for clinical and translational research at the National Institute on Alcohol Abuse and Alcoholism in Bethesda, Md. “You give them a bottle of water and a bottle of alcohol, they’ll always choose the alcohol over the water.”

Researchers have traced this avidity to the hamster’s natural habits. The animals gather fruit all summer and save it for later by burying it underground, where the fruit ferments. “That’s how the hamsters find their cache of last summer’s goodies when it’s the middle of winter,” Dr. Moss said. “They’ve developed a preference for the taste and smell of fruit that’s turned.” They’ve also developed the necessary equipment to metabolize high doses of alcohol. “A hamster’s liver is five times the size of a human liver in comparison to the other abdominal organs,” Dr. Moss said. “It’s all liver in there.”

Behind the hamster dance is the ancient chemical legerdemain of fermentation, which by its most general definition means extracting energy from sugar without using oxygen. There are many ways to do this: our muscle cells ferment when operating anaerobically, say, while lifting weights. The fermentation that yields ethanol, the type of alcohol we drink, is the work of yeast cells, which will latch onto any suitable sugar source and start feasting. As they break down the sugary chains, the yeast enzymes generate two key byproducts: carbon dioxide, which can be used to puff up bread dough, and ethanol. Alcohol, then, is nothing more than fungal scat.

Ah, but how that scat can sing. An alcohol molecule consists of a knob of hydrogen and oxygen linked to a carbon-based stalk, and that telltale knob, that hydroxyl group, allows the molecule to mix easily with water. “The hydroxyl group makes alcohol go to any cell in the body that has water,” said Samir Zakhari, director of the division of metabolism and health effects at the alcohol institute, “which means alcohol goes to every tissue in the body.”

The brain is particularly well lubricated, and alcohol happily mingles therein, to noteworthy, crazy-quilt effect. It stimulates the secretion of dopamine, the neurochemical associated with the brain’s reward system. It stifles the brain’s excitatory circuits and excites the brain’s dampening circuits. It alters the membranes of neurons and the trafficking of important ions like calcium and sodium across neuronal borders. It stimulates like cocaine and it depresses like valium. It makes the shy voluble, the graceful clumsy and the operator of a motorized vehicle very dangerous.

As always, the dose makes the poison, so as you savor the season, take it one small sip at a time.

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