Why do human beings become alcoholics? Specifically, what evolutionary advantage would be conveyed to the species by passing on a genetic predisposition for a love of intoxication? The idea of addictive behaviors having any positive attributes may seem perplexing at first. However, Dustin Stephens and Rodger Dudley offer the intriguing hypothesis that "a strong attraction to the smell and taste of alcohol conferred a selective advantage on our primate ancestors by helping them locate nutritious fruit at the peak of ripeness," as a source of nutrition. (Stephens & Dudley, 2004, p.1) They call this hypothesis, in their memorable and refreshingly colloquial phrase, as opposed to usual scientific jargon, "the drunken money hypothesis." (Stephens & Dudley, 2004, p.1) By seeing alcoholism as a possible evolutionary advantage that has outgrown its primate beginnings, the scientists hope to better understand, destimatize, and offer aid to the estimated fourteen million alcoholics in the United States alone, and the countless other sufferers all over the globe.

             To research and formulate their hypothesis, the authors first examined fossilized primate teeth which showed that fruit had been a major component of the primate diet since the mid- to late Eocene Epoch, between 45 million and 34 million years ago. Ripe fruit and alcohol both have yeasts that consume sugar molecules in the fruit as a source of energy. In a process known as anaerobic fermentation, as fruit ripens, the ethanol content of the fruit rises rapidly. Unripe fruit contains no ethanol, ripe hanging fruit is about 0.6 percent ethanol by weight and overripe fruit can have an ethanol content of more than 4 percent. Alcohol gives the fruit a stronger smell, drawing animals to its ripening state, as well as offers a greater source of caloric energy than unripe fruit.

             To prove their thesis, Stephens and Dudley conducted an experiment on fruit flies of the genus Drosophila, as a kind of primitive research laboratory genetic template of the relationship between sugar preference and ethanol content.