Every time I start to panic, I keep one thought firmly in mind. We have solid evidence that people have been brewing beer for at least 3000 years. I am willing to bet the Chinese were doing it longer than that. They brewed perfectly fine beer with no understanding of yeast, of the chemistry by which starch becomes sugar, no real temperature control, etc..
This mik, is sort of one of cornerstones of brewing philosphy...my mantra...just think of all the things that we have that they didn't...
An understanding of germ theory for one thing...basic sanitition, like regularly washing your hands (remember in many parts of the world centuries ago bathing was thought to be EVIL) so those people fishing their hands into their wort to grab their airlock grommets (j/k) really were at a higher risk of infection than we are....
AND yet...for "BEER" to have survived to be as large a part of the world's culture as it is today...even MOST of their batches had to have turned out OK, meaning it tasted good "enough" and didn't make them sick.....Or else beer culture would have gone extinct...people wouldn't have bothered refining the process if ALL THE BATCHES didn't turn out...
Beer would have gone out of society just like Clear Pepsi and New Coke did...