Yeast strains used today to brew lager have two genetic ancestors, not one as previously thought. The discovery may explain the origins of the two major categories of lager today, described in the trade as the "Saaz" beers such as Pilsner and Budweiser, and the "Frohberg" beers such as Orangeboom and Heineken. It turns out that both probably owe their origins to laws in 16th-century Bavaria that banned brewing in the summer because scorching heat ruined the ale that was brewed before the emergence of lager. Forced to produce their beer in the winter, brewers accidentally created conditions favouring the...