Ales which pre-date lager have traditionally been made using the top-fermenting yeast species Saccharomyces cerevisiae.The origins of the bottom-fermenting lager yeast Saccharomyces pastorianus have long been shrouded in mystery and controversy.However, by combining historical research with modern science, a team of scientists from the Technical University of Munich and University College Cork including myself have uncovered the likely genesis and path to world dominance of S.