The ancient Nubians inhabited an area in which typhus occurs, yet surprisingly few of their skeletons show the usual evidence of this disease  The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil  This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread
Thus, tetracycline in their food probably explains the low incidence of typhus among ancient Nubians
Tetracycline is not rendered ineffective as an antibiotic by exposure to the processes involved in making bread and beer