People have been tossing back beer for thousands of years—the drink is a cornerstone of human civilization—and it’s a potation whose heady qualities come to us by way of yeast. Perhaps most familiar to us in the granulated form stocked on supermarket shelves, yeast is a single-celled microorganism that creates the alcohol and carbon dioxide in beer, in addition to imparting flavors, all of which can vary depending on the type of yeast being used. (More than 800 species of yeast have been documented.) A variety of this fungus commonly used to bake bread and brew ale beers is Saccharomyces cerevisiae, which ferments at a warm 70 degrees. But at some point in the 15th century, Bavarian brewers introduced lager, which employed a hybrid yeast that fermented at cooler temperatures. But what the S. cerevisiae was crossed with to craft this type of beer remained a mystery until now.
Scientists from the Argentine National Council for Scientific and Technical Research, the University of Wisconsin-Madison and elsewhere set out to find where the non-ale portion of the lager yeast came from—and the search took them to Patagonia. Here, in outgrowths on beech trees, they found an undocumented wild yeast—dubbed Saccharomyces eubayanus—whose DNA sequence matched the genome of the unknown half of the lager yeast. They hypothesize that this wild yeast made its way to Europe by way of trans-Atlantic trade and mixed with the baker’s yeast in brewery environments.
But with lagers being brewed before Europeans graced North America, how did this variety of beer initially come to exist? Chris Hittinger, one of the lead scientists on the study, suggests that lagers were made before the arrival of S. eubayanus, and while the beer underwent a long fermentation process in cool temperatures, the resulting brew just didn’t taste very good.