Madison (WKOW) — If you’re planning to open a cold one this Labor Day, you’ll be able to tell a really good drinking story! UW-Madison researchers traced the origins of lager back to 15th century Bavaria.

Scientists found the mysterious hybrid strain of yeast that creates the lagers we enjoy today. Thanks to recent yeast DNA testing, we now know how this favorite libation evolved.

Bubbling with curiosity… “I think it’s a pretty fascinating case,” said UW professor Chriss Hittinger.

After circling the globe, “it gives you something to think about as you sit down in these waning days of summer and wonder where your crisp lager came from.”

Hittinger now knows the backstory to the world’s top brew. “I really wanted to make sure it would serve as a resource,” he said. It took four years of genome sequencing to unlock answer: “this marriage between two yeast species…as divergent as humans and birds are,” he said.

Ale yeast — and the missing lager link: saccharomyces eubayanus. And as it turns out, “they’re not nearly as discriminating as you and I about mating with one another.”

Most yeast will thrive around 80 degrees, that’s what these heaters are set at. But saccharomyces eubayanus thrives at 40 degrees, so doctors can isolate it. “We’ve been able to isolate even very rare forms of it, even here in Wisconsin,” said Hittinger.

But it all began back in Bavaria with the monks. “The additional ale strains were not well adapted, so it had to hybridize with another strain…and that’s saccharomyces eubayanus.”

And the rest is history: “they created a stable hybrid that created a quarter trillion industry.”

But the work continues in the lab: right now they’re using this yeast’s ability to deal with the cold, to see if it can tolerate toxins used in making biofuels.