Alcohol comes from a simple natural process: yeast feeds on sugar and produces ethanol and carbon dioxide as byproducts. This process, called fermentation, happens spontaneously in nature whenever ripe fruit splits open, and humans have been harnessing it deliberately for at least 9,000 years. Today, alcohol is produced through both traditional fermentation (for beverages) and industrial chemical synthesis (for fuel, solvents, and sanitizers).
Fermentation: The Basic Chemistry
Every alcoholic drink starts with sugar and yeast. Yeast is a single-celled fungus that eats carbohydrates like glucose, fructose, and sucrose. When oxygen is limited, yeast can’t fully burn those sugars for energy the way your muscles burn calories during exercise. Instead, it takes a shortcut: it partially breaks the sugar down, releasing a small amount of energy for itself while leaving behind ethanol and carbon dioxide as waste products.
This is why bread rises and beer bubbles. The carbon dioxide inflates dough and carbonates drinks, while the ethanol gives alcoholic beverages their effect. In bread, the ethanol evaporates during baking. In beer or wine, it stays.
Yeast can process a wide range of sugars, including those found in ripe fruit, honey, grain starches that have been broken down by malting or enzymes, and plain table sugar. The type of sugar source is what distinguishes one category of alcohol from another: grapes give you wine, barley gives you beer, apples give you cider, and so on. But the underlying chemistry is identical every time.
There’s a natural ceiling to fermentation. As ethanol accumulates, it eventually becomes toxic to the yeast itself, killing it off and stopping the process. Most wine and beer yeast strains top out between 12% and 18% alcohol by volume. Anything stronger than that requires distillation.
Alcohol Exists in Nature Without Humans
Fermentation doesn’t need a brewery. Wild yeast lives on the skin of fruit, and when fruit ripens, splits, or falls to the ground, those yeasts go to work on the exposed sugars. Researchers studying a Neotropical palm fruit found that ripe fruit contained about 0.9% ethanol in the pulp, while overripe fruit averaged 4.5%, roughly comparable to a light beer.
Animals encounter this naturally fermented fruit regularly. Many primates, birds, and insects eat overripe fruit and consume small amounts of ethanol in the process. Some researchers have proposed that the ability to detect, tolerate, and even seek out ethanol may have been shaped by natural selection in fruit-eating species over millions of years, since the smell of alcohol signals ripe, calorie-rich food from a distance.
The Oldest Known Alcoholic Drinks
The earliest physical evidence of deliberate alcohol production comes from southern China. At the Qiaotou archaeological site, researchers analyzed residues inside painted pottery vessels dating to roughly 9,000 years ago. The pots contained traces of a beer made from rice, a grain called Job’s tears, and starchy root vegetables. Even more striking, the residues showed evidence of mold cultures, specifically types consistent with Aspergillus and Rhizopus, being used as a fermentation starter. This is the same basic technique still used to brew rice-based alcohols in East and Southeast Asia today, predating the earliest written records of the method by about 8,000 years.
From China, the Middle East, Africa, and Central America, archaeological evidence shows that virtually every early agricultural society independently figured out how to make alcohol from whatever starchy or sugary crops they had on hand. Barley beer and grape wine appeared in the ancient Near East. Corn-based drinks emerged in Mesoamerica. Fermented mare’s milk was produced on the Central Asian steppes. The process was so simple that discovering it was nearly inevitable once people began storing fruit or grain.
Distillation Changed Everything
For most of human history, the strongest drinks available were wines and strong beers topping out around 15% alcohol. Distillation broke that limit. The technique works by heating a fermented liquid until the ethanol evaporates (ethanol boils at a lower temperature than water), then cooling the vapor so it condenses back into a much more concentrated liquid.
The first clear description of distilling pure alcohol from wine came from the Arab scholar al-Kindi, who lived from roughly 801 to 873 CE. He built on earlier work by Jabir ibn Hayyan (known in Europe as Geber), and his writings represent the first unambiguous account of producing relatively pure distilled ethanol. From the Islamic world, distillation knowledge spread to medieval Europe, where it gave rise to brandy, whiskey, gin, vodka, and every other spirit.
How Industrial Alcohol Is Made
Not all ethanol comes from fermentation. A large share of the world’s ethanol, particularly the kind used for fuel, sanitizers, and industrial solvents, is synthesized from petroleum byproducts. The most common method is the hydration of ethylene, a gas derived from oil refining. By combining ethylene with water under high pressure and temperature in the presence of a catalyst, manufacturers produce ethanol without any yeast or sugar involved.
The scale of industrial ethanol production is enormous. In 2024, the United States alone produced over 16 billion gallons of ethanol, the vast majority of it corn-based fuel ethanol blended into gasoline. Brazil produced nearly 9 billion gallons, mostly from sugarcane. Together, the two countries account for about 80% of global output. China, the European Union, and Canada round out the major producers. Only a fraction of this total is beverage alcohol; most goes into fuel tanks.
How Your Body Processes Alcohol
Once you drink alcohol, your liver does most of the work to eliminate it. The process happens in stages. First, an enzyme in your liver converts ethanol into a compound called acetaldehyde, which is highly toxic and classified as a carcinogen. This is the substance responsible for much of the damage from heavy drinking, though it normally doesn’t stick around long. A second enzyme quickly converts acetaldehyde into acetate, a much less harmful substance. Acetate then gets broken down into water and carbon dioxide, which your body easily disposes of.
This two-step process is why some people react badly to even small amounts of alcohol. Genetic variations in either enzyme can slow down one step relative to the other. If your body converts ethanol to acetaldehyde quickly but clears acetaldehyde slowly, it builds up, causing facial flushing, nausea, and a rapid heartbeat. This variation is particularly common in people of East Asian descent. Your liver also recruits backup enzyme systems when you drink heavily, but these secondary pathways handle only a small fraction of the total and come with their own metabolic costs.