History of baking dates back to 8000BC, when men used to crush grains on stones into small pieces, add water to obtain dough and cook it with fire on flat rocks. Primitive human beings broke the collected grain into small pieces; so they could either chew or digest it without making it soft. The founders and developers of bread making and bakery certainly experienced a series of trial and error processes.
Yeast was known in pre-historic times. Sources indicate that the history of bread goes back to 8000BC and the history of yeast to 3500BC. Archaeological excavations identified that yeast was used before 2000BC in Babylonia and ancient Egypt.
Ancient peoples were interested in yeast as it rapidly consumes sugar and produces CO2 (carbon dioxide) and causes the leavening of bread.