Of all the varieties of beer that exist, lager is probably the most maligned by craft beer aficionados. Mass market lagers are criticised for their uniformity and bland fizziness; microbrewed ones are almost nonexistent because lager is expensive to brew. The bulk of the lagers on the market in Australia conform to a very narrow range of the style: pale lagers rather than the traditionally German dunkels, märzens or schwarzbiers. It is the international style that now dominates the local brews and faux imports alike. They’re crisp, unvarying and unchallenging.

The strains of yeast used to brew a lager thrive at low temperatures, generally between 7 and 15 degrees celcius. Brewing away at lower temperature causes yeasts to grow more slowly. Traditional lagers like marzen (which means “March” in German) were stashed in cool caves in March and disgorged from the casks for Oktoberfest. It is a costly process to replicate because of the need to keep the beer stored at a low temperature while the yeast eats its way through the sugars in the beer.

Lagers have been brewed in Germany since the 1400s but one of the mysteries behind the beer is how did the particular strain of lager yeast get to Germany. This year, we came one step closer to finding out. The LA Times reports:

Geneticists have known since the 1980s that the yeast brewers use to make lager, S. pastorianus, was a hybrid of two yeast species: S. cerevisiae — used to make ales, wine and bread — and some other, unidentified organism.

Searching through collections of wild yeasts from Europe, researchers — including Hittinger and his collaborators — tried to identify lager's missing link but again and again were stumped. "There were a few candidates, but none fit particularly well," Hittinger said.

So he and his colleagues began "sampling more systematically," collecting soil and bark, sap and abnormal growths called galls from trees on five continents.
Team member Diego Libkind of the Institute for Biodiversity and Environment Research in Bariloche, Argentina, found S. eubayanus in galls on southern beech trees in Patagonia. The galls were particularly rich in sugar, which yeast like to colonize and consume.

Patagonian natives used to make a fermented beverage from the galls — a definite clue that the scientists were on the right track, Hittinger said.
When the team brought the yeast to a lab at the University of Colorado and analyzed its genome, they discovered that it was 99.5% identical to the non-ale portion of the S. pastorianus genome, suggesting it was indeed lager yeast's long-lost ancestor.

What makes this fascinating for one of the world’s more boring beers is that somehow, the yeast from Patagonia has made its way from the Americas to Germany in the early 1400s. There is a possibility that the bacteria existed in an as yet undiscovered location in Europe, but the first European to make that passage was Christopher Columbus in 1492. The small unknown in history suddenly makes lager look a little more interesting.