The study is a sign that fermented foods—including bread and soy sauce, besides alcoholic beverages—altered our biology, or at least the biology of microscopic creatures that live in constant contact with us. Life in the human gut isn't always easy. Sure, the food comes to you, but it's of such a variety that it's difficult for any one creature to digest it all. Before the invention of fermented foods and beverages, human gut bacteria would have encountered alpha-mannans only rarely. Those that figured out alpha-mannans, however, got a boost as soon as people began consuming bread and beer all the time.