I had a very interesting wander through the Internet the other day, sparked by a BBC news report.
The workhorse of brewing, the yeast Saccharomyces cerevisiae, is used worldwide to ferment fruit and grains to make wine, cider and ale.
Lager, which is fermented more slowly and at lower temperatures than ale, is presumed to be a later invention, and was likely stumbled upon when Bavarian monks moved their beer barrels into caves for storage.
In those caves, Saccharomyces cerevisiae, which prefers to grow just above room temperature, is presumed to have been outcompeted in the fermenting beer by a species that thrived at cooler climes.
The modern-day lager-brewing yeast, Saccharomyces pastorianus, which is a fully domesticated species, is probably a hybrid of this cool-loving strain and the ale-brewing species, and survives because brewers keep back a little of the lager each time to seed the next batch with the same yeast.
"The hybrid almost definitely formed accidentally and people adopted it because the beer came out differently," said evolutionary biologist Chris Hittinger from the University of Wisconsin in Madison, US, who was one of the team behind the discovery.
But researchers have long wondered where the original cool-loving yeast species came from.
That is until Dr Hittinger and his colleagues isolated it from a beech tree in the forests of Patagonia this year.
These forests, where daily lows average around -2C, are the perfect cradle for modern-day lager-brewing yeast. The species has been designated Saccharomyces eubayanus.
"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," Dr Hittinger told BBC News.
There's more at the link.
This led me to look up 'lager' on Wikipedia, which informed me:
While cold storage of beer, "lagering," in caves for example, was a common practice throughout the medieval period, bottom-fermenting yeast seems to have emerged as a hybridization in the early 1400s.
I speak Afrikaans, a colonial derivative of Dutch used in South Africa, but I'd never made the connection between 'lagering' - storing - and the name of a variety of beer. I also knew the word 'laager', meaning a fortification made of wagons pulled together, which is also derived from 'lagering' - in that particular usage, a place of safety for its defenders. Interesting that a fort, a storage place and a beer all have a common origin for their names!
Now I'm left to wonder . . . just how, precisely, did a Patagonian yeast make its way across the Atlantic to Europe in an age before transatlantic voyages were possible? I daresay I'll never know, but the possibilities for speculation are endless! Beer-loving aliens in flying saucers, perhaps?