In the days before science, humans turned to religion for explanations. It also inhibits the growth of microorganisms, but some of these dormant germs can become dangerous when the food is rehydrated. Heat can increase shelf life by temporarily sterilizing food. But our ancient ancestors could not adequately cook many plant foods until they developed pottery and cooking vessels. Humans developed rudimentary cold storage by cooling the recesses of caves and other shelters with ice and snow.
Fermentation is a gradual chemical change caused by the enzymes of some bacteria, molds and yeasts.
Fermented beverages were common in the earliest civilizations of Mesopotamia and Egypt. Not only did wine facilitate conviviality, it was usually more potable than the available water. Winemaking was also a means of storing nutrients from grapes almost indefinitely. Similarly, Asian steppe dwellers turned mare's milk into koumiss, a fermented beverage that keeps much longer than unprocessed milk. Many cheeses with a long shelf life are produced by lactic-acid fermentation.