For thousands of years brewers made beer using specialized strains of the budding yeast Saccharomyces cerevisiae. The historical origins of brewer’s yeast are not well understood, however, as brewing predates the discovery of microbes. A new study publishing March 5 in the open-access journal PLOS Biology, led by Justin Fay at the University of Rochester, shows that modern brewing strains were derived from a mixture of European grape wine and Asian rice wine strains. This finding points to the emergence of beer yeast from a historical East-West transfer of fermentation technology, similar to the transfer of domesticated plants and animals by way of the Silk Route.