How would our world be different if humans did not discover how to use yeast thousands of years ago?

what is yeast? a microscopic fungus consisting of single oval cells that reproduce by budding, and are capable of converting sugar into alcohol and carbon dioxide.

Explanation:

ok so it would be different because we wouldnt have alchool and carbon dioxide and sugar would be useless

Once upon a time there were no farms. People ate fruit off the vine and killed animals as they ran. They roasted things when it suited them but just as often ate them raw. The world was like this for thousands of years, a place of arrows and nuts where everything that was necessary could be found. One might imagine many reasons for giving up on those old, superficially idyllic, ways. Perhaps it was hunger, that ultimate mother of invention, or maybe it was just invention itself, unmotivated by need.