Take Two Beers and Call Me in 1,600 Years

Natural History, May, 2000 by George J. Armelagos

But none of this told us why the antibiotic was showing up in the ancient bones. In nature, tetracycline is produced by streptomycetes, moldlike bacteria commonly found in soils. These slow-growing cells do not do so well in the wet, acidic soils where most bacteria flourish, but they have the edge in hot, dry, and neutral-to-alkaline environments. Ten-year-old spores survive in dry sand and are easily cultured.

Initially we thought that during famine or drought, the ancient Nubians and Egyptians might have been forced to eat moldy grain. (Even one or two grams of tetracycline consumed by humans in a single day will produce fluorescence in bone.) The warm, dry, alkaline environment of storage bins made of mud could have been an ideal environment for streptomycetes. But we learned that when they are growing well, streptomycetes actually produce little tetracycline. Given the degree of tetracycline labeling in the Nubian and Egyptian remains, we had to consider other possibilities. The key turned out to be beer, known as bosa in much of present-day Africa.

Searching through both ancient and later texts, Everett Bassett, Margaret Keith, and other members of our team realized that in the region's grain processing, there was an important link between bread baking and beer brewing. Egyptian art also shows baking and brewing in constant association. In fact, baked bread is an essential part of the traditional beer recipe still used today by villagers who live along the Nile.

The beer produced in ancient times, according to Barry Kemp, author of Ancient Egypt: Anatomy of a Civilization, was quite different from the modern commercial product: "It was probably an opaque liquid looking like a gruel or soup, not necessarily very alcoholic but highly nutritious. Its prominence in the Egyptian diet reflects its food value as much as the mildly pleasurable sensation that went with drinking it." University of Cambridge archaeologist Delwen Samuel and his colleagues from the British brewery Scottish and New-castle have undertaken extensive research on brewing and baking in ancient Egypt. They analyzed the remains of food left in tombs as offerings and the residues of beer and crumbs of bread encrusted on pottery shards and vessels. They even examined floor sweepings from tombs and living areas.

Successful brewing depends on the use of a grain that provides enough sugar for fermentation. In modern recipes, grain is made to germinate and is then heated and dried to halt the process. Known as malting, this procedure releases the enzyme diastase, which converts the starches in grain to maltose sugar. The malt is then boiled, strained, and incubated with yeast. In the traditional Egyptian method, bread dough is set out to capture airborne yeast. (Other traditional recipes actually add bosa that was held back from previous batches for this purpose, since the liquid contains yeast.) When baked, the bread forms a crust but is removed from the oven before the center has had a chance to cook, allowing the yeast to grow in the warm, slightly cooked dough. The partially baked bread is then broken up and added to a broth of malted grain to make the beer.