Sourdough is basically a “wild” yeast and is floating in the air everywhere. It can be traced back to Egyptian times and is referenced in the Bible. You have heard of unleavened bread...surely it was discovered (by accident) that leaving the dough (or use potato water, or flour/water mixed) out for a few days attracted the wild yeast bacteria. The feeding by-product was gas bubbles and then heating the dough accelerated the bubble action; thus, producing a rising of the dough (leavening) and the unique flavor of sourdough which was lighter and tasted better than the hard stuff.
The advantages of having a “kept” starter are that it becomes stronger and more reliable. And all starter is not the same. It evolves with environmental changes. San Francisco sourdough is slightly different from Alaska sourdough which is different frommy Costa Rican strain. Differences in water, flour, temperature, etc. will produce a slightly different (unique) strain. So, basically, I have a world strain that produces some delectable edibles.