The first civilizations arose when cultivated grains were first used to make bread. The earliest attempts, during the Stone Age, involved placing lumps of unleavened dough on a hot stone over a fire, (early
ancestors of pita, chapattis and tortillas).
Later it occurred to someone to invert a pot over the dough while it was cooking, this drew the dough upwards and the resulting bread was lighter. The first rudimentary bread oven had been invented.
But how was the first loaf of bread leavened? It can only be surmised that some dough was left out on a sunny day, it fermented and the resulting bread was further improved. Probably the Egyptians were the first to put two and two together and realize that there was a connection between beer and leavened bread.
The Greeks and later the Romans turned bread baking into an art; techniques and ovens were improved, new ingredients added and new breads created.
Leavened bread became the staple food of the masses, many survived on a hearty loaf a day.
For centuries wheat flour ,(particularly white flour) was considered a luxury only the rich could afford. The poorer folk depended on barley, rye or other grains. This all changed with the Industrial Revolution which brought artificial methods of crop fertilization and new machines to plant or reap square miles of wheat in a matter of hours. Not to even mention the new roller mills. For the first time in history white bread was the cheaper alternative.
Fortunately in the past few years there has been a renewed interest and preference for organic stone ground flours, rustic grains and supporting bakeries who bake the original way.