Today, we drink the wine of ingenuity. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

The ancient discovery of fermentation spawned all kinds of foods. Two ferments are very old: leavened bread and fermented honey. Yeast, or leaven, generates carbon dioxide in bread. It makes the bread rise. It gives it a light texture. Unleavened bread is dense and hard. It makes biscuits or crackers.

The first fermented drink had to be a form of mead -- a ferment of wild honey. Before agriculture, it was the only foodstuff that would've given a natural ferment. That's why honey-mead owns such ancient and mystic symbolic power.

Neolithic farmers soon learned to ferment their newly domesticated grains and grapes. Biblical accounts of early man mention alcohol some 250 times -- usually wine, but beer and vinegar as well. Some versions talk about strong drink, but that's misleading. Distillation was a medieval invention. No one made really strong drink before the 13th century.

Natural ferments of sugary fruit juices or honey go in two stages. The first stage produces alcohol. The second forms acetic acid -- vinegar. The trick is to stop fermentation before the second stage can take place. The easiest way to do that is by sealing the container before vinegar can be formed.

The Egyptians were already making several kinds of beer when they began recording their own history. They were also making wine from dates, honey, and even milk. Their hieroglyph for the word brewer showed a man straining mash into a vat. The process changes slightly in Sumerian hieroglyphs.

So fermenting was a highly refined art in the ancient world. Biblical references to wine take two forms. Usually it's a symbol of good and of plenty. But we're also warned, over and over, to take it easy. "Wisdom hath mingled her wine," says the Book of Proverbs. That's a simple warning to mix water with wine before we drink it.

Vinegar was the strongest acid in the old world. It was widely used in medicines. Many of its chemical properties were also known. One of the Psalms warns against mixing an acid and a base: "Like vinegar poured on soda is one who sings songs to a heavy heart," it says.

Natural ferments have an odd place in human history. They've engaged human ingenuity since recorded time. Their variety goes on and on. I've drunk beer made from bread in Russia and wine made from cactus in Mexico. Ferments make foodstuffs that are both honored and dangerous. But that's in the nature of technology itself. What technology pleases the mind and the senses without requiring caution along the way?

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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Singer, C., Holmyard, E.J., and Hall, A.R., A History of Technology. Vol. I, New York: Oxford University Press, 1954, Chapter 11.