The oldest method of processing food, except for fire, of course, is wild yeast. In fact, the Mesopotamians first used yeast to brew beer as long ago as 6000 B.C. However, it wasn't until three thousand years later, when the Egyptians experimented with cooking methods, that someone figured out that yeast could be used to make bread rise.
The ancient Greeks and Romans, being a bit more flamboyant, at least as far as bread is concerned, embellished on Egyptian bread "recipes" and added olives, various fruits, seeds, and herbs to their own concoctions, thus coming up with something more elaborate.
We do know that the development of sourdough bread came much, much later. What isn't known, however, is if the invention of this very tasty bread came about because someone was an inspired chef who decided to use old, souring dough from a previous loaf of bread to create something new and different, or whether the creator or the sourdough bread many of us love so much was just a very lazy cook. Whichever, we owe him, or her, a debt of gratitude. (Although I'd love to believe the "inventor" was an inspired chef, I'm betting it was a very lazy cook or a cook who sadly, at the time, at least, had far too little with which to work.)
The first recorded instance of the use of sourdough bread occurred when the ships of the Spanish Armada arrived in the US with a sourdough starter pot. From that time on, there was no looking back.
California's gold rush played a part in making San Francisco the "home" of sourdough bread in the US when the Boudin family, master bakers from France, arrived in the area. Intrigued by the taste and uniqueness of sourdough, they established a bakery and their bread soon became famous, especially with the miners who crowded their shop every morning. This bakery, which is still famous in San Francisco, has been using the same "Mother dough" starter since 1849. The recipe was almost destroyed in the Great San Francisco Earthquake of 1906, however Louise Boudin, recognizing its importance to her family, risked her own life to save it
Bread is one of life's staples. If you want to be taken seriously as a cook, especially a gourmet cook, you'll master the art of bread making. And if you want to include one of the tastiest and best loved of all the various breads, you'll master the art of making sourdough.