<P> Bread was central to the formation of early human societies . From the western half of Asia, where wheat was domesticated, cultivation spread north and west, to Europe and North Africa . This in turn led to the formation of towns, as opposed to the nomadic lifestyle, and gave rise to more and more sophisticated forms of societal organization . Similar developments occurred in eastern Asia, centered on rice, and in the Americas with maize . </P> <P> There is extensive evidence of breadmaking in Ancient Egypt in the form of artistic depictions, remains of structures and items used in bread making, and remains of the dough and bread itself . </P> <P> The most common source of leavening in antiquity was to retain a piece of dough (with sugar and water in) from the previous day to utilize as a form of sourdough starter . Pliny the Elder reported that the Gauls and Iberians used the foam skimmed from beer to produce "a lighter kind of bread than other peoples ." Parts of the ancient world that drank wine instead of beer used a paste composed of grape must and flour that was allowed to begin fermenting, or wheat bran steeped in wine, as a source for yeast . </P> <P> The idea of a free - standing oven that could be pre-heated, with a door for access, appears to have been Greek . </P>

When did they figure out that yeast made bread rise
find me the text answering this question