Scientists have identified a yeast that led to the discovery of lager. The researchers isolated the new species in the frozen forests of Patagonia in South America. Their discovery suggests that this yeast crossed the Atlantic hundreds of years ago and combined with one traditionally used in Europe to make ale. The discovery is described in the Proceedings of the National Academy of Sciences. Marco Werman interviews Chris Todd Hittinger, a genetics scientist and co-author of a study on lager yeast.