The Evolution of Beer: Yeast DNA Reveals Origins in 15th-Century Bavaria

Beer is enjoyed by Americans across the United States. But where did beer, in general, first get its start? And how did it develop into the brew that it is today? Researchers have taken a closer look.

The beer world is divided into ales and lagers-and both boil down to the highly versatile yeast, Saccharromyces cerevisiae. This yeast has been used for millennium to create ales, wine and bread. It's this yeast, in fact, that began the evolution of beer.

But there was a bit of innovation in the 15^th century. That's when Bavarians first noticed that beer stored in caves during the winter continued to ferment. The result was a lighter, and smoother beer that later went on to dominate the 19^th and 20^th century beer tastes, especially in America.

Lager yeasts are actually hybrid strains made up of two different yeast species, S. cerevisiae and S. eubayanus, which was discovered in 2011. Lagers now represent about 94 percent of the world beer market, though the origin of different hybrid lineages has been a point of contention among lager beer makers. Now, though, researchers have attempted to solve the mystery.

The scientists took advantage of the newly described wild yeast species, Saccharomyces eubayanus in order to complete and assemble a high-quality genome of S. eubayanus. They then compared the genome to domesticated hybrids that are used to brew lager style beer, which allowed them to study the genomes of both parental yeast species contributing to lager beer.

So what did they find? There were two independent origin events for S. cerevisiae and S. eubanyus hybrids that brew lager beers.

"Lager yeasts did not just originate once," said Chris Todd Hittinger, one of the researchers, in a news release. "This unlikely marriage between two species, genetically as different from one another as humans and birds, happened at least twice. Although these hybrids were different from the start, they also changed in some predictable ways during their domestication."

The findings reveal a bit more about the evolution of beer and show that yeast species actually evolved at several different points.

The findings are published in the journal Molecular Biology and Evolution.

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