The Conundrum Of Corn

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In 1748 an inquisitive Swede named Peter Kalm, a protégé of the great botanist Linnaeus, came to America to find plants that could be useful in his country. He went around asking questions of everybody about everything. He asked Benjamin Franklin about hardy trees and was told that English walnuts did not survive Philadelphia’s winters. He asked John Bartram, the most knowing botanist in the colonies, about timber and was told that American oaks were not as tough as European. He asked Cadwallader Golden, later to become the lieutenant governor of New York, about medicinal plants, and was informed that the root of skunk cabbage helped cure scurvy.

But the answer to one question eluded Kalm. Everywhere he went he asked about maize, or Indian corn. He found out the Indians baked it into bread (adding huckleberries in season), brewed it into beer (blue-colored corn was best for this), and used it as a poultice (for curing boils). But he was balked when he asked the simple question Where did corn come from? A blackbird brought it from the west, said some Indians. A beauteous maiden shook it out of her hair, said others. These answers, of course, did not satisfy Kalm’s Enlightenment mind.

Scientists today can appreciate his frustration. Ever since he asked it, they have been repeating his simple question—where did corn come from?—and after two centuries or so have come up with only half the answer. After long deliberation, they have pretty much agreed that corn came from this continent—not from Asia as some once thought— and grew originally in middle America. That settles the geographical question but not the genealogical one: What is corn’s ancestry? The search for the answer has sent botanists into fruitless hunts for hypothetical wild grasses and put geneticists through tedious evolutionary exercises in breeding corn backwards. It pits three main schools of thought against each other—Mangelsdorf versus Beadle versus Weatherwax. And it provokes long seminars in which, sooner or later, someone refers to the “mystery of maize.”

It seems strange that so familiar and open a plant as corn, whose very name is a metaphor for the obvious, should have any mystery about it. Everybody knows corn. It is a staple crop not just in Nebraska but in Bulgaria, Nigeria, and Thailand. A highly adaptable plant, it grows from Canada to Chile, in humid sea-level marshes and rarified Andean plateaus. A most amenable plant, it breeds so readily and crosses its genes so promiscuously that any kind of corn for almost any purpose can be created. Universally useful, it fattens hogs and cows while nourishing man with tortillas and polenta, enlivening him with beer and bourbon, and holding things together in wallpaper paste and jelly beans.

Nonetheless, corn still presents a mystery, and smack in the middle of it is a Mexican weed called teosinte. A tall, tasseled plant that is found in and around cornfields, it looks so much like corn in its early stages that farmers neglect to pull it out. It pollinates corn freely and just as freely is pollinated by it. Modern corn, in fact, has some teosinte in its genes. Teosinte is so much like corn in so many ways that everyone agrees it is a relative of corn. But which relative? The Beadle school says teosinte is the ancestor of corn. The Mangelsdorf school argues, instead, that corn is the ancestor of teosinte. The Weatherwax adherents say that corn and teosinte descend from some common ancestor, making them cousins.

A hundred and fifty years ago it was believed that a primitive kind of corn named pod corn was the wild progenitor of modern corn. Then, later in the nineteenth century, when the relationship of corn and teosinte was recognized, the teosinte-as-ancestor theory took hold. In 1939 Paul Mangelsdorf of Harvard and R. G. Reeves of Texas went back to the pod corn theory.

After amassing persuasive genetic and botanical evidence for their belief, they found concrete support in archaeology. It came first in 1948 from the Bat Cave in western New Mexico, where prehistoric Indians lived from about 3000 B.C. to A.D. 1000. The leftovers of their tenancy lay untouched in the cave floor—layer after layer of garbage, offal, excrement, broken pottery. Digging methodically, excavators found 776 corncobs. Not a single one had a kernel left on it. But over the centuries 125 kernels had been carelessly dropped and overlooked by beetles and rodents (though back at Harvard, where they were studied, modern mice got into the cache of ancient kernels and ate several). At the bottom were tiny cobs, five thousand years old. In the oldest remnants, there was no indication of teosinte. An even older find was made by an expedition working caves at Tehuacán near Oaxaca in Mexico, where diggers uncovered a seven-thousand-year-old cob. From all the evidence, Mangelsdorf concluded that this was wild corn. And when drillers in Mexico City found grains of cornlike pollen at soil levels eighty thousand years old, long before man came to America, Mangelsdorf was sure of his thesis. The ancestor of corn, he said with finality, was corn.