A lcohol is a clear, thin, odorless liquid that is produced by fermentation. Fermentation is a chemical reaction that occurs naturally when yeast, a microscopic plant that floats freely in the air, reacts with food that contains sugar. Fruits and berries have sugar in the form of fructose, which ferments as they become overripe due to yeast. Grains from wheat, rye, and barley also have natural sugars that can be transformed into alcohol as they age. Birds can become drunk from eating such fermented foods, and biologists have observed that animals in the wild sometimes become intoxicated in the same way.

How or when people first discovered how to control the fermentation process is unknown. However, historians know that people have been drinking alcoholic beverages for thousands of years. In Alcohol: The Delightful Poison, historian Alice Fleming explains...