Yeasts capable of leavening bread are widespread, and in the many centuries during which the ancient egyptians made only unleavened bread, such yeasts must frequently have been mixed into bread doughs accidentally. the egyptians, however, did not discover leavened bread until about 3000 b. c. that discovery roughly coincided with the introduction of a wheat variety that was preferable to previous varieties because its edible kernel could be removed from the husk without first toasting the grain.