In trial-and-error fashion, it must have dawned
upon the ancient beverage-maker that by adding
grapes to any mixture of other less-sweet ingredients—
berries, barley malt, wheat—the prospects of
producing a fermented beverage were improved. It is
even possible that the frothy yeast that bubbled on
the surface of a mixed beverage of grapes and other
materials was skimmed off and used in later fermentations.
Gradually, in this seemingly nonhygienic,
experimental setting, a single yeast species came to
predominate and was shared by the whole range of
fermented beverages: S. cerevisiae.