Dominic Ashworth

What has woken up is yeast. Yeast is a fungus, a single-celled relative of mushrooms, so small that a teaspoon of the dried kind holds billions of cells. The species bakers use, and brewers too, has been with people for thousands of years, long before anyone knew it was alive. The Egyptians were baking risen bread by the second millennium BC. They would have known that a scrap of yesterday's dough, kept back and mixed into today's, made the new batch rise. They would not have known why.

Dominic Ashworth

This is fermentation, the same process that makes beer and wine, and the resemblance is not a coincidence. For most of history, bakeries and breweries stood near each other and traded. Brewers skimmed the froth off their vats and bakers bought it as "barm". The neat packets of dried yeast in a supermarket are a twentieth-century development; the organism in them is the same old one, selected over generations for reliability.