The drunken monkey hypothesis proposes that human attraction to ethanol alcohol may have a genetic basis due to the high dependence of the primate ancestor of Homo sapiens to fruit as a food source. Ethanol naturally occurs in ripe and overripe fruit and consequently early primates developed a genetically based attraction to the substance.This hypothesis was originally proposed by Dr. Robert Dudley of the University of California at Berkeley and was the subject of a symposium at the meeting of the Society for Integrative and Comparative Biology. Dudley believes that while most addictive substances have a relatively short history of use, ethanol attraction may have a long evolutionarily based history. He believes that fruit ethanol may have been a significant source of calories and that the smell of the ripening fruit would help primates locate it. Primates are known to have a higher olfactory sensitivity to alcohol than other mammals. The once-beneficial attraction to ethanol may underlie human tendencies for alcohol use and alcohol abuse.