A friend on our long journey
The close relationship humans share with yeast is truly ancient, and predates humanity itself. (photo by Lilly M via commons.wikimedia.org)
During the holiday of Passover, we are told not to eat leavened bread (chametz). The leavening of bread is caused by yeast, a single-celled fungus. The yeast induce a chemical reaction called fermentation, which converts water and sugar into alcohol and carbon dioxide. The bubbles of carbon dioxide gas produced during this reaction cause the bread to rise and become porous, ultimately resulting in delicious fluffy bread. The close relationship humans share with yeast is truly ancient, and predates humanity itself.
Since fungi lack mobility, it had often been assumed that they were more plant-like than animal-like. But genetic studies in the 1990s revealed that fungi are actually more closely related to animals than to plants. The common ancestor that animals and fungi share would have probably been single-celled, and resembled in many ways our friend the yeast. So we can consider them very distant cousins (not invited to the Passover seder).
Fruit are an important part of the diet of all apes, including humans and their ancestors. A ripe sweet juicy fruit is full of sugar and water, the key ingredients for fermentation. There are many different varieties of yeast that are found commonly all over the world, on the human body, in the soil, and often on the skin of fruits. Fermentation of ripe fruits due to the presence of such yeast is common in nature, and would have inevitably been eaten by the ancestors of humanity for millions of years. Primatologists have observed various species of monkeys getting drunk off such naturally fermented fruit. To explain this puzzling phenomenon, biologist Robert Dudley at University of California-Berkley formulated the “drunken monkey” hypothesis. Fruit evolved as a means for plants to use animals as a method of seed dispersal; however, if the fruit rots before it gets eaten, the seed doesn’t get dispersed. Alcohol is a volatile molecule, which means it floats around the air very easily. If a fruit begins to ferment, the alcohol molecules spread much further and faster than the smell of the fruit would on its own. Animals, such as monkeys and apes, can, therefore, smell from a greater distance that there is delicious fruit, helping them find and eat the fruits, and thus helping to disperse the seeds of the plant. It is an evolutionary relationship that benefits the plant, the yeast and the animal, a win-win-win scenario.
Moderate consumption of alcohol is in fact healthy and nutritional. Alcohol contains more calories than either carbohydrates (sugar) or proteins. Let us remember that calories were integral to survival before the obesity epidemic of the modern age. Alcohol can also protect against many diseases, especially cardiovascular diseases. Studies have even shown that people who consume alcohol in moderation live longer than those who don’t. Despite the many dangers associated with excessive alcohol consumption, the low doses normally consumed in nature ultimately may have provided a survival advantage to the ancestors of humanity.
The first civilizations arose in part due to intensive cereal agriculture. These cereals were used to make bread and beer. In Mesoamerica, they made a beer from corn, in China with rice and, in Mesopotamia and Egypt, they used barley and wheat to make beer and bread. These innovations that played an integral role in the building of civilization were thanks to yeast. The first writing system ever developed was Cuneiform, in Mesopotamia during the third millennium BCE. Among the first written records in history are references to the production, distribution and consumption of beer. Some scholars suspect that the Jews acquired this beer brewing knowledge during their exile in Babylon. The Hebrew word for drunk, shikur, is thought to be derived from the Babylonian word for beer, shikaru. However, if the story of Passover is to be believed, then perhaps the ancient Israelites brought the knowledge for beer making from Egypt.
Wine, an essential component of any decent Passover seder, also has an ancient history. The earliest evidence for intensive wine production can be found at the archeological site of Hajji Firuz Tepe in modern-day Iran, which has been dated to sometime around 5400 BCE. Genetic analysis corroborates that strains of wine yeast originated in Mesopotamia, but put the date back 10,000 years ago. Some archeologists have speculated that the strains of yeast used for making bread and beer originated from wine yeasts, however the evidence for this remains contentious. Wine and beer were both produced in Egypt, and were important culturally, religiously and medicinally, and Egyptians would bury jars of wine in the tombs of the pharaohs. Analysis of DNA found inside ancient Egyptian wine jars from the tomb of a pharaoh from 3000 BCE identified the same species of yeast used to make wine today: Saccharomyces cerevisiae.
If there were indeed Jewish slaves in Egypt, they would have eaten bread and drank beer and wine, leavened and fermented by the same fungus that we use to leaven bread and ferment wine today; a little old friend that has joined us on our long journey through the vast deserts of time. L’chayim.
Ben Leyland is an Israeli-Canadian writer, and resident of Vancouver.