Paleogenetics ─the study of ancient DNA─ has revealed that ADH genes are present in several branches of the tree of life, from plants to fungi and animals, underscoring the capability of many organisms to metabolize alcohol (8–12). The well-documented consumption of alcohol from food sources such as fermenting fruits by some non-primate animals (e.g., birds and fruit bats) (13–16) led to the hypothesis that exposure to ethanol-rich food environments favored the evolution of traits associated with ethanol metabolism (17), and the ability to detect its sensory properties. Locating the source of alcohol would be evolutionarily advantageous in leading the organism to an abundance of food high in sugar and carbohydrates (18). However, ADH genes predate natural ethanol availability, a finding that refutes this hypothesis (19). Notwithstanding, although ADH activity is widespread in the phylogenetic tree, there is a great diversity of ADHs within and across species, including encoding genes, their structure, and tissue expression (19).
