The evolutionary ecology of ethanol production and alcoholism

Understanding the evolutionary ecology of ethanol production may yield insights into why humans are prone to excessive consumption of ethanol. In particular, Dudley (2000) suggested that human ancestors developed a genetically based attraction to ethanol because they could use its odor plume to locate fruiting trees and because of health benefits from its consumption. If so, ethanol should be common in wild fruits and frugivores should prefer fruits with higher ethanol content. A literature review reveals that ethanol is indeed common in wild fruits but that it typically occurs in very low concentrations. Furthermore, frugivores strongly prefer ripe over rotting fruits, even though the latter may contain more ethanol. (Data on ethanol content of ripe and rotting wild fruit are lacking.) These results cast doubt on Dudley's hypothesis and raise the question of how humans became exposed to sufficiently high concentrations of ethanol to allow its excessive consumption. Because fermentation is an ancient and widespread practice, I suggest that humans "discovered" ethanol while using fermentation as a food preservation technique. They may have been predisposed to consume ethanol from previous and beneficial exposure to much lower doses or they may have become addicted to it at high concentrations because of fortuitous physiological responses.