The identity of the key yeast behind the creation of lager beer has been a long-standing mystery, but now scientists claim that they have unmasked the micro-organism.

Scientists isolated the new species in the frozen forests of Patagonia, Argentina, in South America. The discovery indicates that this species of yeast crossed the Atlantic hundreds of years ago and joined the traditional one that was being used in Europe to create ale.

The brewing yeast, called Saccharomyces cerevisiae, is used around the globe to ferment grains and fruit to brew cider, wine and ale.

Lager-brewing, which is considered to be a later invention than ale, is fermented at lower temperature and more slowly than ale. It is believed that the lager-brewing yeast was likely accidentally found when Bavarian monks stored their beer barrels in caves.

In those caves, Saccharomyces cerevisiae was surpassed in the fermenting beer by a species that used to thrive at cooler temperatures.

Evolutionary biologist Chris Hittinger, of the University of Wisconsin in Madison, US, said that the hybrid was definitely formed accidentally and it was adopted as the beer came out differently.

Speaking to BBC News, Dr. Hittinger said, "I personally prefer lagers to ales, and I am very grateful that these two distant cousins met up in a Bavarian cellar hundreds of years ago.”

Lager beer, most probably the most popular alcoholic beverage in the world, wouldn’t have been possible without the strange arrival of that yeast.