The oldest archeological evidence of beer brewing in Germany dates back to 800 BC. If you visit the Bavarian Beer Museum in Kulmbach, you can view the earthenware amphora (a container that looks like a cross between a vase and a bowl) that bore testament to the earliest known German brews. When the amphora was excavated in 1935 from a Celtic burial mound in the Bavarian village of Kasendorf, archeologists found residue of black wheat ale flavored with oak leaves.
Later, and before the discovery of yeast in the 19th century, Germans would brew beer by crumbling a loaf of half-baked bread into crocks of water. If airborne yeast cells found their way into the mix, fermentation would begin and beer would result.
But neither of these concoctions would be legally considered beer in Germany today, where a law that began with the Reinheitsgebot—or German Beer Purity Law—dictates that beer contain only water, barley, and hops. The Reinheitsgebot originated in Bavaria in 1516 and was written by Duke Wilhelm I in Ingolstadt.
Sources vary on the reasoning behind the law. Some say it was intended to keep the price of bread affordable by forcing brewers to leave grains like wheat and rye to the bakers. Others posit that the law was created in order to ensure the safety and quality of beer by excluding dangerous ingredients that could sometimes cause hallucination. It is considered the oldest food regulation law in the world.
Similar laws eventually spread throughout Germany, and they have evolved with the country. When yeast’s roll in brewing beer was discovered, it was added to the list. Various local laws were incorporated into the Beer Taxation Law (Biersteuergesetz) in 1952 which reinforced the dictates of the Reinheitsgebot with similar regulations.
In 1993 the Vorläufiges Biergestzt introduced an expanded version of the Reinheitsgebot into law. It restricts bottom-fermented beer to water, malted barley, hops, and yeast, while top-fermented beer can contain other kinds of malt, as well as sugar. Though the law has changed over the years and the Reinheitsgebot is technically no longer in effect, many German brewers still advertise their adherence to its “purity” standard.