Who Figured Out How to Make Leavened Bread?

Someone had to be the first person to figure out yeast. What do we know about the first sourdough starter?

A loaf of leavened bread against a yellow background
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In the Old Testament story of Exodus, once the pharaoh finally agreed to let the Israelites go—after the plagues of frogs, boils, lice, and more—the Israelites justifiably feared he would change his mind. And so they fled. They left in such haste, according to the Old Testament, that they didn’t even have time to let their dough rise.

I have always thought a bread making detail like the timing of a dough’s fermentation seemed like an odd way of illustrating the Israelite rush. But as I’m now discovering, there’s a link between long hours in one’s dwelling and the comfort of guiding a dough’s slow rise. Over this past month, as a plague has kept me home, I’ve found myself in somewhat of the reverse bind of the Israelites. And my response has been to do what they could not: reach into the back of my fridge and refresh my old sourdough starter.

Of course, I’m not alone in making fresh bread. By some estimates, yeast sales have increased as much as 600 percent over the past month. From a strictly practical perspective, this doesn’t actually make much sense. Fermentation adds almost no nutritional value to bread, so if this were simply about calories in a time of crisis, there are far more efficient options. But of course, it’s not just about calories. Leavened bread is a culture, a comfort, and a celebration. It’s an art as much as it is a food. And it turns out it began that way.

For my book Who Ate the First Oyster? I learned about all kinds of ancient inventors and their discoveries—from who rode the first horse to who wore the first pants—but America’s quarantine-inspired embrace of baking made me wonder: Who discovered the magic of yeast and dough, started the first sourdough starter, and baked the first leavened loaf?

As the bioarcheologist Andreas Heiss notes, baked bread is one of the most elaborate, time-consuming, and difficult cereal foods you can make. So when the first bread makers—a group of hunter-gatherers living in the Middle East 14,000 years ago now called the Natufians—baked the first flatbreads, they made them as celebratory foods, not as staples. Bread began as the Natufian version of our wedding cake. It was the decorative food of ceremony, not a rational expenditure of effort for calories.

Yet there’s no evidence the Natufians leavened their bread, the archaeobotanist Amaia Arranz Otaegui wrote to me in an email. When she examined the world’s oldest crumbs she found no hint of yeast, and besides, she adds, the Natufians did not have the domed ovens needed to properly bake a leavened loaf.

Domed ovens, and not coincidentally leavened bread, did not arise for another 5,000 years. Yet ovens did not invent leavened bread—they simply made it possible.

Risen bread required an inventor. A culinary champion. Someone with an adventuresome palate to combine their artistry with their courage in a moment of carelessness.

Who was this ancient hero, and how did she invent the leavened loaf?

Let’s call her Mary, after Mary Berry, the baker and co-host of The Great British Baking Show whose work this extended quarantine has provided me the time to enjoy. And I’ll call Mary a “her” because there’s at least some evidence from Neolithic skeletons that women processed the bulk of the cereals. Though gender roles in ancient times remain somewhat of a mystery, one study by the researcher Theya Molleson of London’s Natural History Museum found that Neolithic women more frequently suffered from the kinds of osteoarthritis in their toes and lower backs that indicate grinding seeds using the awkward and physically demanding querns and hand stones of the time.

Mary would have spent considerable time grinding those wheat and barley seeds because she was one of the first farmers in human history. She lived approximately 9,000 years ago in the Neolithic era, a time when archeologists believe a few people living in a few small villages became the first to transition from hunting and gathering their food to farming it. These small communities near the Euphrates and Tigris rivers in the Middle East’s fertile crescent are where archeologists have found some of the oldest evidence of farms, domesticated animals, and domed ovens.

As a farmer, Mary probably spent her days gathering and planting seeds, caring for her fields, and—for special occasions—baking flatbread and brewing beer. (Archeologists suspect that because beer is merely liquid bread left out to rot, the Natufians discovered flatbread’s far more exciting counterpart shortly after their first bake.) With beer, bread, and her oven, Mary had all the necessary ingredients to ferment dough. She just needed a moment of convergence and daring.

Dough needs a large dose of yeast to rise. The microscopic amounts that ride on dust and in the bellies of insects wouldn’t have been sufficient to leaven her flatbread before she baked it. So scholars have searched for other, larger sources of yeast to explain her discovery of leaven—and a few have turned their gaze to beer. Nicholas Money, a botanist and the author of The Rise of Yeast, believes Mary may have stumbled onto leavened bread by accidentally splashing a beer’s yeast-laden froth onto her dough. If she did, the result would have been a fungus explosion within her flour and water.

As yeast feeds, it multiplies. Its cells grow bulges called “schmoos,” and these schmoos then smooch other schmoos, fuse, fertilize, and bud new cells. Those first few hours after Mary’s accident would have been an orgy of smooching schmoos. In the proper conditions, two days can turn 100 yeast cells into 400 billion.

The amount of fermentation these microorganisms can perform in a short time is astounding. As Louis Pasteur later described it to a skeptical audience in 1854, a yeast’s work rate on glucose is the equivalent of a 200-pound person chopping 2 million pounds of wood in two days.

Within an hour or less, depending on the size of the initial splash, the yeast’s carbon dioxide would have noticeably ballooned Mary’s dough. Up until this point, Mary deserves little credit for what took place. What had happened probably wasn’t even unique. But whereas most bakers would have thrown out the puffy aftermath of their mistake, Mary had the nerve and the stroke of genius to place hers in the oven.

The result would have been magical.

Unlike the Natufian hearths, Mary’s domed oven would have achieved the high heat necessary to quickly turn water to steam and expand the yeast’s small carbon dioxide bubbles into giant holes. The bread would have doubled in size before her eyes. And when Mary had the courage to try it, instead of crunching a flat, dense bread, she would have torn into a delicious, airy loaf. Clearly, she would have tried her recipe again, probably spilling yet more froth onto her dough and enjoying even greater results.

Her technique may have even endured. In one of the oldest descriptions of leavened bread, the Roman philosopher Pliny the Elder describes how the Gauls used foam from their beer to bake what he called “a lighter kind of bread than other peoples.”

Eventually Mary or another baker learned you could hold back a portion of yeasty dough and add it to the next day’s bake, enabling a more consistent rise. And perhaps another bacterium floated into the starter, one like Lactobacillus, which instead of alcohol produces lactic acid to ward off competitors—and the first sourdough starter was born.

So as you’re baking in quarantine, thank Mary and the other Neolithic bakers who learned how to leaven bread. If you’re not in a rush, it tastes as good today as it did 9,000 years ago.