Drunken monkey hypothesis

The drunken monkey hypothesis proposes that human attraction to alcohol may derive from dependence of the primate ancestors of Homo sapiens on ripe and fermenting fruit as a dominant food source. Ethanol naturally occurs in ripe and overripe fruit when yeasts ferment sugars, and consequently early primates (and many other fruit-eating animals) have evolved a genetically based behavioral attraction to the molecule.

Source: Wikipedia — Drunken monkey hypothesis (CC BY-SA 4.0)