Aerobic fermentation is essential for multiple industries, resulting in human domestication of several yeast strains.  Beer and other alcoholic beverages, throughout human history, have played a significant role in society through drinking rituals, providing nutrition, medicine, and uncontaminated water.  During the domestication process, organisms shift from natural environments that are more variable and complex to simple and stable environments with a constant substrate. This often favors specialization adaptations in domesticated microbes, associated with relaxed selection for non-useful genes in alternative metabolic strategies or pathogenicity.  Domestication might be partially responsible for the traits that promote aerobic fermentation in industrial species.  Introgression and HGT is common in Saccharomyces domesticated strains.  Many commercial wine strains have significant portions of their DNA derived from HGT of non-Saccharomyces species.  HGT and introgression are less common in nature than is seen during domestication pressures.  For example, the important industrial yeast strain Saccharomyces pastorianus is an interspecies hybrid of S. cerevisiae and the cold tolerant S. eubayanus.  This hybrid is commonly used in lager-brewing, which requires slow, low temperature fermentation.