Ha! As I wrote yesterday, researchers in yeast genetics are changing the story on the history of yeast all the time, and the day I put that post up, new findings on the genetics of lager yeast came out which, as New Scientist reported, take the hybridisation narrative further down the road to a fascinating destination.
To quote New Scientist, Gavin Sherlock and Barbara Dunn of Stanford University, California, compared the genes of 17 lager and ale yeast strains across the world, with origins dating from between 1883 and 1976, and derived from breweries as diverse as Carlsberg and Labatt, Rainier and Heineken:
It has long been thought that Saccharomyces pastorianus, the yeast used in lager production, formed only once from the hybridisation of S. cerevisiae and S. bayanus. Instead, the team discovered that it happened at least twice in two separate locations in Europe, giving rise to the two different lager families … The hybrid, which makes lager instead of ale, probably evolved in Bavarian beer-brewing cellars during the 16th century.
The team also found that Saaz yeasts have a single copy of each parent yeast’s genome, whereas the Frohberg yeasts have an extra copy from S. cerevisiae. They believe this difference affects the flavour of the lager, as well as how quickly the yeasts can ferment the hops
[my emphasis, and sic, fer gawd's sake. Bloody journalists ... do they know nothing?]