Our research is aimed at understanding the molecular basis of evolution. Yeast species in the "model genus" Saccharomyces possess a unique set of features that make them an ideal system for studying evolution in the laboratory. Yeast is a well characterized eukaryote microorganism with a short doubling time. Saccharomyces yeasts can be propagated either sexually or asexually and either as haploids or diploids. In addition, populations can be frozen creating a "frozen fossil record" of adaptive evolution. These tools allow us to watch evolution in real time as well as to analyze the historical events that led to the modern yeast species.