As per experts today several kinds of beer exists, including ales, lagers, pilsners, and ciders, to name the most popular few. It is believed that years of brewing may have led to the selective evolution of genes that are key to making this beer.

Lager beer is loved by people across the globe. Now, new research explains how different strains of yeast came to be (particularly those used to make lagers), which had been something of a mystery. Typically, lagers utilize yeasts that could ferment at lower temperatures, a process that gives them their distinctively crisp taste.

In 2011, Hittinger’s team figured it out: a species called Saccharomyces eubayanus, discovered, oddly enough, on the sides of beech trees in chilly Patagonia, in South America. [Raise Your Glass: 10 Intoxicating Beer Facts].

The crucial genetic mashup that spawned the yeast that brews the vast majority of beer occurred at least twice – and both times without human help – according to a University of Wisconsin-Madison study published August 11 in the journal Molecular Biology and Evolution. For those who don’t know: worts are grain mixes containing sugars which get fermented into alcohol after coming in contact with the yeast.

It wasn’t until the late 19th century that yeast was identified as the culprit of fermentation. They were also able to resolve a question about the two major lager yeast lineages, Frohberg and Saaz, discovering that the two had separate origins, not a single precursor, as some groups had hypothesized.

Lager yeasts are hybrid strains, made of two different yeast species, S cerevisiae and S eubayanus, which was discovered in 2011.

The results suggest the Saaz and Frohberg lineages – named after their area of origin in Bavaria – were created by at least two distinct hybridisation events. Hittinger reveals that the S. cerevisiae was adapted for Mediterranean temperatures and this is the reason why bread, wine and ale beers are present for a thousand years. They compared it to domesticated hybrids, which are used to brew lager, allowing for the first time the ability to study the complete genomes of both parental yeast species contributing to lager beer.

Each lineage is a hybrid of two yeasts that have not mated with each other, likely because each is sterile and only reproduces asexually. For instance, yeast cells can sexually reproduce when they are starved of nitrogen and carbon.

“It’s the same idea”, Hittinger said.

Lager yeast evolved in a way that pleased many beer palates, the researchers said. Lagers now represent a whopping 94 per cent of the world beer market.

Elizabeth Goldbaum is on Twitter. “That provides potentially a large reservoir of genetic diversity, some of which could have interesting flavor profiles”.

Understanding the evolutionary pattern of yeast is important “to learn how to take advantage of it for beverages and fuels”, Hittinger said.

The evolution of beer yeast