The origin of cold-adapted yeast that blended with a distant cousin to make your favourite lager beer has been found in 500-year-old caves in south America.
An analysis of the yeast's genetic sequence revealed its closest affinity to one of two highly diverse Patagonian populations.
It confirmed it was the cold-loving microbe that 500 years ago found its way to the caves and monastery cellars of Bavaria where lager beer was first concocted.
Patagonia is a region located at the southern end of south America shared by Argentina and Chile.
"Saccharomyces eubayanus, the wandering parent of hybrid lager yeast discovered in 2011, is indeed a native of Patagonia," said Chris Hittinger, a professor of genetics at University of Wisconsin-Madison.
By exploring yeasts' native habitat and looking to see where else in the world they have turned up, scientists may unlock secrets of yeast genetics and hybridisation with enormous economic benefit.
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"Yeasts are important for fermenting processes and biotechnology. The value of studying diversity is that you can pull out genes or strains that can be used for a particular industrial process," genetics graduate student David Peris noted.
Brewers and winemakers have unwittingly selected it for hybrids.
The tools of modern biotechnology can potentially refine industrial fermentation by mixing and matching genes that lead to a better conversion of sugar to alcohol, Hittinger commented in a study in the journal Molecular Ecology.