(WashingtonPost) - Humans and microbes go way back. The bacteria, yeast and viruses that live in and on and around us have incredible sway over the way we live. But when it comes to culinary pursuits, yeasts stand out as our most stalwart cooking companions: These tiny creatures consume sugar and produce gases and alcohol as waste, giving our breads the bubbles of air that make them fluffy and delicious and lending beer its foamy, boozy power.

According to research published Thursday in the journal Cell, humans have been domesticating the yeast used to make beer — breeding it for the properties that suit our needs — since the 16th century. That means we were breeding yeast for their beer-making qualities for over a century before scientists actually discovered microbes.

Humans started brewing beer thousands of years ago, probably in ancient Egypt. Without any knowledge of the microorganisms powering their breweries, it's no surprise that the first tipplers worked blind, brewing with whatever wild yeasts found their way into the brewing process. But according to genetic analysis of over 100 yeasts used by industrial brewers today, brewers started unknowingly breeding the best yeasts sometime around the 1500s.

"Brewers were smart enough to realize that if they used the sediment found at the end of the fermentation process, if you used it to inoculate a new batch, the fermentation will go much quicker," explained study author Kevin Verstrepen, a yeast geneticist at the University of Leuven and VIB in Belgium. "And when you take the sediment from a really nice beer, the new batch will for the most part turn out pretty nice."

They didn't know it, but these early brewers were selecting the fittest beer yeasts, which settle down into sediment after they stop producing gas. By putting them into a new batch of beer (a process known as back-slopping), the brewers were keeping their favorite strains of yeast warm and well-fed, encouraging them to reproduce.