Where do tribal people or ancient cultures get yeast for making wine or beer?!
Answers: How do isolated people around the world and our ancestors get the yeast to make alcohol when they couldn't just go to the store and buy it?
Yeast occurs naturally in the environment. When certain foodstuffs were stored in specific environments, they often became contaminated by types of yeast literally floating around in the air. People found that the foods were changed in ways they came to like. Most 'wild' strains of yeast aren't as effective as the highly selected varieties we use today, but they do work. What's more interesting is that many uses of yeast were established for centuries before the yeast itself was discovered.
It's in the air, everywhere.
Its a naturally occuring organism. In many instances, ancient cultures didn't know what yeast was or that it was responsible for the fermentation process.
Yeast is often found naturally on grapes so that accounts for the wine. I think the beers were made by just letting the liquids ferment naturally and seeing what comes out. There is enough yeast found naturally in the air that fermentation is always going on with sweet liquids.
Yeasts are not man-made. They occur in nature everywhere.