Ale is the beer classification that predates written history. Presumably, the very first beers brewed by our hominid forebears were a crude form of ale spontaneously fermented by wild airborne yeasts. These yeasts became known as top-fermenting yeasts for their propensity to float on top of the beer as it’s fermenting. Hence, ales are, likewise, considered top-fermented beers.
Until the invention of the microscope in the 18th century, brewers didn’t know exactly what yeast was or how it fueled fermentation, they just knew it did — and they were grateful. They even called it Godisgood!
Dating back into antiquity, most ales were thick and gruel-like, often containing bits of the grain that was used to make the beer and opaque from the yeast that fermented it. (Archaeologists and anthropologists have determined that people used straws to drink the beer from huge communal bowls.) Ales were also fairly dark and often smoky due to the process of drying the grain over a fire. In Scotland, where grain was dried over peat fires, the local ale took on the character of its sister swill, whisky.
The basic premise of brewing ales is to ferment them at fairly warm temperatures (55 to 70 degrees Fahrenheit, 12 to 21 degrees Celsius). At these temperatures, the yeast tends to remain quite active, thus completing the fermentation process in rather short order — in about a week or so.
Pretty much any beer style introduced prior to the advent of artificial refrigeration in the 1800s qualifies as an Old World ale style; however, those ale styles that are on the lighter end of the color spectrum, as well as those styles that are served crystal clear, have certainly benefitted from the technologies of our modern era. Beers are no longer all dark and smoky and cloudy, thanks to state-of-the-art grain drying apparatuses and filtration systems.
Not unlike the wild-fermented potions brewed by our Neolithic ancestors, some commercial brewers still produce their unique ales in a very antiquated and somewhat risky way. After brewing their beer, they pour it into large, shallow, open-topped vessels and allow Mother Nature to take over. Resident microflora find their way to the unprotected beer and have their way with it, producing some of the most odd and esoteric — not to mention sour — beers on the planet. Aging and blending soften some of these ales’ acidic sting, but they still qualify as an acquired taste.
Very few brewers produce spontaneously fermented beers in the world, and the one thing they all share is the importance of their breweries’ location.