I just read Bread: A Global History by William Rubel and "Barms and Leavens -- Medieval to Modern," an article about bakers' yeast, brewers' yeast, and sourdough starters, by Laura Mason, in the collection titled Over a Red-Hot Stove: Essays in Early Cooking Technology edited by Ivan Day. Here's a photo of these two books sandwiching a few other books about bread:
Rubel's first chapter presents the prehistoric origins of bread. He writes: "Long before the Neolithic Revolution, when the hunters and gatherers in the Fertile Crescent made the cultural shift to farming and raising large animals..., the peoples in the region were harvesting and eating grains from vast fields of wild barley and wheat." He sets the earliest date for some type of bread-making in this region at 22,500 years ago, explaining that both wheat and barley, when winnowed, ground, and perhaps roughly sifted, could be used for a dough that would form "an aerated crumb, not a dense mass of starch." Archaeology identifies grindstones and traces of hearth fires that confirm this early bread-making. One major theme of his work is that early examples of bread were not necessarily primitive or crude: early people had and used tools and ingenuity to make bread that was tasty by modern standards, and moreover, was often visually creative in its decorative uses.
Both Rubel and Mason explore at length the chemistry of bread-making. Mason's concentration is on the historic use of various substances to raise dough, mainly in England, and on the flavors and varieties of bread that resulted from the choices of housewives, noble kitchens, or professional bakers. The early bakers depended on either yeast -- which came from brewing beer or ale -- or on sourdough starter -- which resulted from exposing dough to ambient yeasts and bacteria. Both types of leavening resulted in a variety of flavors; only in the last 200 years or so has yeast exclusively intended for baking bread been prepared, preserved, and sold. Chemical baking powder is very recent, and is barely mentioned in either source.
Rubel discusses the same choices in a number of historical and modern contexts, exploring not only the taste and chemistry, but also the social and cultural associations of various types of bread. He makes a case that the past 40 years or so have been a time of very rapid change in bread consumption and in worldwide changes in taste in bread, and especially in the globalization of some types of bread with the possible decline of some local products.
Some tastes come and go, for example in some eras bread made from yeast has been highly prized, while in other eras, including the present, a higher value has been placed on sourdough. Also, some bakers cultivate practices that make sourdough bread more sour or less sour -- the famous Poilane bread (described in one of my books depicted) is much less sour than the well-known San Francisco sourdough breads. Mason interestingly pointed out that sourdough, relying more on bacteria, facilitates baking with non-wheat flour such as rye, while yeast creates less of a rise in rye or other grains.
My previous favorite bread history was H.E.Jacob's Six Thousand Years of Bread. The two more recent works are much more scientific, and more based in analytic archaeology than in Jacob's more mystical views of bread, though his descriptions are very fascinating. All these books have a large and interesting amount of information and historic detail -- the subject seems almost inexhaustible.