I read that it may well be that the US-05 origin is not SN but European. I dont’t think we’ll ever know for sure.
My Bloody Ballantine: Hunting Down the Origins of US-05 — Blog — Anspach & Hobday | London Craft Brewery
That A&H blog is a worthy attempt to write up what can be Googled about the origins of Chico, but there's a fair bit of it that's completely wrong. I once tracked down the exact paper that YeastWhisperer had misread to come up with the idea that Chico is diploid. It isn't, it's just a regular tetraploid(-ish) like almost any other
cerevisiae, but diploid Chico seems to have entered conventional wisdom.
Ultimately, if you go back far enough in the sense that all humans come from the Rift Valley,
S.cerevisiae comes from the Far East nearly a million years ago. But in terms of human domestication, the origins of modern brewing yeasts are a few hundred years ago in the triangle between London, Hamburg and Munich - roughly corresponding to the western end of the Hanseatic League and its hinterland. So in that sense, modern brewing yeasts are all "European".
You've got to be a bit wary of interpreting genetic history at this kind of deep level, but what seems to have happened is a big breakthrough with the selection of the first non-phenolic yeast probably in Germany, which probably looked like a somewhat more estery kolsch yeast. Being non-phenolic, lots of people will have harvested it and wanted to brew with it, so it will have ended up mutating away independently in lots of separate vats in different breweries.
One of these "kolsch-ish" yeasts got lucky multiple times. And since genetics is mostly a numbers game, that suggests this yeast was in a brewery that was the Renaissance equivalent of Bass or Urquell, the one that got everywhere - maybe it was a royal/government/navy/army brewery, maybe it had an exclusive deal with the Hanseatic merchants, maybe they were just really good at marketing or had the advantage of making a beer with hops in that could survive long-distance trade better than unhopped ales. Regardless, their yeast got lucky and one assumes was widely harvested. One batch was brewed in a cold cellar on the Continent and it hybridised with a cold-adapted
S. eubayanus to start the lager family of yeasts, in another vat somewhere it stole a chromosome arm from a saison/wine yeast to start the hefe family. And another barrel was exported to Britain and its yeast ended up being the ancestor of the yeasts that ferment the majority of British ales today.
Again, I'll repeat the caveat about the uncertainty in this kind of deep history. But once it got to Britain, the first group to split off seems to have been the WLP028 Edinburgh group, followed by the ancestor of WLP025 Southwold. Later the main group of British brewery yeasts evolved, and seem to have acquired more flavour character. But it's the ancestor of WLP025 that's interesting as it's also the ancestor of WLP008 East Coast and the Chicos, and a more recent ancestor of WLP025 is also the ancestor of WLP009 Australian Ale.
This does not mean "Chico came from Adnams" - not least because Adnams only got their current yeast from Morgan's Brewery of Norwich in 1943, just before Morgan's was destroyed in an air raid. But it does suggest that the Adnams-Morgan yeast is a bit of a living fossil, like the coelacanth, that illuminates evolutionary history. And it suggests both Chico and some "Australian" yeasts came from somewhere exporting to both Australia and the East Coast of the US, possibly at different times, possibly from different breweries. Now obviously Germans have played a huge role in US brewing, and
Dutch were required to pay rent in beer in New Jersey in 1638, but
British colonists appear to have been deliberately farming hops in Connecticut by 1661, and
by the early 1700s there was a huge amount of trade in beer from the UK and within the 13 Colonies. So my guess would be that the "US" family of brewing yeast dates from Britain at this kind of time rather than it coming from Europe within the lifetime of Ballantine as a company. If you forced me to speculate, it probably originated in a barrel from one of the towns like Dorchester or Taunton that were famous for their beers at the time, and close-ish to the ports from which colonists departed. But that is pure speculation.
