Like living organisms, the evolution of beer styles follows a principle called “punctuated equilibrium.” This principle states that while conditions remain unchanging, there is little evolutionary change besides random drift. However, when conditions do change, entities either adapt, radiate to fit changing niches, or get pruned back as unfit. With long-dormant American beer, real changes started in the 1970s.
The explosion of artisanal beer continues today, propelled by homebrewers and those who would try to make a living out of it. However, the earliest of these beers were inspired by European ones—especially British ales. Perhaps it’s an expression of the American character to turn a glass full of inspiration into something new and different, but these beers were not painstaking facsimiles of European standards. They were re-imaginings.
Anchor Brewing cast the die in 1972 with a total remake of their historic Steam Beer—switching to all-malt, tossing in some exotic crystal malt, then balancing it with the weirdest hop they could find at the time, a new variety called Northern Brewer. This outline became the rule for most pale ales, IPAs, barleywines, and others in the family ever since. In 1975, Anchor followed up with Liberty Ale—an American IPA, and the first in modern history.