Ethanol derives from the fermentation of simple sugars, and fermentative yeasts are ubiquitous within terrestrial ecosystems. Animals that consume sugar-rich fruits and nectar thus routinely ingest low-level ethanol; the positive psychoactive responses to ethanol among vertebrate fruit-eaters (and modern humans) act to increase net caloric gain during feeding via the aperitif effect. Early primates (and more recently the great apes) predominantly consumed ripe fruit, suggesting chronic exposure to fermented carbohydrates along with natural selection for the rapid localization and consumption of these calorically rich substrates. Patterns of alcohol use by modern humans may thus reflect ancestral sensory biases associating ethanol consumption with nutritional reward (i.e., the "drunken monkey" hypothesis).

Robert Dudley is a Distinguished Professor in the Department of Integrative Biology at the University of California–Berkeley, and a Research Associate at the Smithsonian Tropical Research Institute in Panama. He received an B.S. in Zoology from Duke University in 1983, and a Ph.D. in 1987 from the University of Cambridge where he was a Marshall Scholar. He then lived on Barro Colorado Island in Panama for five years, working as a Smithsonian Institution postdoctoral fellow on butterfly flight biomechanics. Robert's research is primarily concerned with the evolution, physiology, and biomechanics of flight in insects and hummingbirds.  His current work focuses on the biomechanical origins of flight in birds and insects, and on the amazing flight performance of hummingbirds, a species-rich avian group which exemplifies up-regulated physiological and aerodynamic capacity. In addition to studying animal flight, Robert has pioneered research into the comparative biology of dietary ethanol consumption, with particular reference to primate frugivory. This work, summarized in his 2014 book (The Drunken Monkey: Why We Drink and Consume Alcohol) provides a new hypothesis to explain routine low-level consumption of alcohol as well as the persistence of alcohol abuse in modern humans.