Imagine for a moment that you are not an evolutionarily tuned great ape, with dazzling cognitive powers and the foundation of all human civilization beneath your feet, but rather a simpler, more purposeful organism. Imagine you are a single cell of Saccharomyces cerevisiae, newly roused from your dormancy and afloat in a sugar- and nutrient-rich soup cooked up especially for you.
At first, you’re sluggish and weak. Yet you are driven by a biological imperative to which even the greatest apes are sympathetic, and you seek what your cell requires to grow stronger. Vitamins, minerals, and oxygen are crucial, and you feed voraciously, yet still the pounding drum of biology reverberates through your being. Survival is not enough, and you begin to change. A lump forms on your cell membrane. This bud swells and grows, filling with cytoplasm until your very core splits in two. A chunk of your cell’s nucleus migrates to the bud, carrying a copy of your genetics with it. Soon your bud has grown to match your own cell in size, and this daughter cell detaches, taking your DNA with her into the future.
Meanwhile, your mothers and sisters teeming around you in the billions feast and bud as well, churning the medium with gaseous excretions and clumping together in ad hoc colonies. Brewers call it high kräusen—but yeast, if they had a language of their own, would call it one hell of a party. The biomass of yeast in the tank explodes logarithmically, doubling the number of cells every few hours as the sugars in the medium are consumed. What was once sterile wort is transformed into beer, as the monocellular population produces ethanol, carbon dioxide, and a virtually uncountable catalog of flavor compounds.