This is difficult to answer because we have to find some kind of historical record of when (and how) such fermentations were being done. Written documents are good sources of information (they are dated and can be cross-referenced to other evidence), but if - as in this case - the discovery predates writing, meaning to say, the discovery was done before humans kept records, then we have to look at other physical evidence. For example, did a particular prehistoric society keep containers (jars) that could be imagined as specifically designed to hold alcoholic beverages, or did prehistoric societies use alcoholic liquids for other purposes (like solvent for dyes or paint). Using such evidence, we might be able to pinpoint the era that alcoholic substances made their first appearance, and then we could investigate what technologies were available at that time that could be used for fermentation.
I think you will find that if you tried to track down such evidence, there is a general uncertainty as to when and how fermentation happened. At this point we are left with speculations and arguments … and without strong evidence, that's no longer science.
Greg (Roberto Gregorius)
That's a very good, but difficult question. Fermentation happens naturally in nature. Just when people first figured out what caused it, and then figured how to do it for themselves is a difficult question.
Certain berries, and even grapes, have yeast that causes fermentation growing on their skin. As the berries get over ripe they begin to ferment. Birds sometimes eat these berries and are seen getting drunk!
In a way, fermentation preserves food. Wine lasts longer before going "bad" as compared to grape juice. Even when it "goes bad" the wine gives us a useful liquid called vinegar.
Who or when the first person sampled those over ripe berries and figured out how to harness the fermentation is lost because it was so long ago. Let's just say that we've had fermented drinks for a long time.
By the way, fermentation is the thing that makes yeast bread rise. It's just that in baking, all the alcohol boils away.
Hope this helps, at least a bit.
Oklahoma State University Institute of Technology
Grape skin has a wax that attracts a natural yeast. You may have seen it as a slight, whitish film on the grapes.
In the olden days, farmers picked grapes, placing them in wooden vats to be sold at market. They noticed that when grapes were not sold as fresh, the grapes would swell, become broken and take on an acetic and alcoholic fragrance. As they cleaned the old vats, the top where the air was, smelled acrid, like that of vinegar. At the bottom of the vats(no air) the alcohol fragrance was particularly noted.
The farmers didn't really worry - vinegar was sold to make pickles and the wine was used for medicines.
As time went on, farmers began placing lids on the vats and allowed them to warm in the sun - not allowing the air inside the vat. There, they began to manufacture wine. These farmers were the first wine makers.
It was hundreds of years later that biochemists began to understand the background and chemistry of wine making.
Peter E. Hughes, Ph.D.