As long ago as 200,000 years, a Neanderthal couple with kids in tow, found a new cave to move into. (Note if you do not believe in evolution this never happened; if you are fanatically religious it happened about 3,000 years ago) Anyway, said couple has moved in, and the female is having her mate move the rocks into different spots, clear out dead animals, rearrange the moss, etc. He spots a rainwater-filled depression in some rocks outside, that has collected a bunch of overripe fruit from nearby trees.
Drawn by the sickly-sweet smell, he tastes the fermented liquid, and is intrigued by the new, unusual taste and not-unpleasant burning in his throat. He then notices something - his mate's voice now does not sound so shrill; the throbbing in his head is diminished. A few more drinks and he does not care what she is having him move around in the cave. A few more sips and she looks more and more like what she did when he met behind the tar pits, lo those many, many moons ago.
So here is to that unknown ancestor who first discovered one of the beneficial uses of alcohol - I lift my glass to you.