(Eurekalert) - Humans aren't the only species that like to get busy with a glass of bubbly, according to researchers at the Stanford University School of Medicine. Turns out, the common baker's yeast has indulged in a frenzy of amorous frolicking in the fermentation vats of winemakers for hundreds, possibly thousands, of years, with interesting results. The unexpected promiscuity has made the lineage of many commercial and wild yeast strains difficult to trace. But there are also indications that such willy-nilly sharing of genetic information is precisely what gives that hint of passion fruit to your favorite glass of chardonnay, or that round, plummy flavor to your most-recent quaff of zinfandel. "The strain of yeast used in fermentation definitely affects the flavor of the wine," said Gavin Sherlock, PhD, an associate professor of genetics who personally taste-tested several vintages specially produced by his Gallo collaborators as part of the research, "and we thought that these strains would fall into a nice evolutionary-tree-like structure with a common ancestor."