At Home - Bill Bryson [21]
However they did it, the Mesoamericans created the world’s first fully engineered plant—a plant so thoroughly manipulated that it is now wholly dependent on us for its survival. Corn kernels do not spontaneously disengage from their cobs, so unless they are deliberately stripped and planted, no corn will grow. Had people not been tending it continuously for these thousands of years, corn would be extinct. The inventors of corn not only created a new kind of plant, they also created—conceived from nothing really—a new type of ecosystem that existed nowhere in their world. In Mesopotamia natural meadows grew everywhere already, so cultivation was largely a matter of transforming natural grain fields into superior managed ones. In the arid scrubs of Central America, however, fields were unknown. They had to be created from scratch by people who had never seen such a thing before. It was like someone in a desert imagining lawns.
Today corn is far more indispensable than most people realize. Cornstarch is used in the manufacture of soda pop, chewing gum, ice cream, peanut butter, library paste, ketchup, automobile paint, embalming fluid, gunpowder, insecticides, deodorants, soap, potato chips, surgical dressings, nail polish, foot powder, salad dressing, and several hundred things more. To borrow from Michael Pollan, author of The Omnivore’s Dilemma, it is not so much as if we have domesticated corn as it has domesticated us.
The worry is that as crops are engineered to a state of uniform genetic perfection, they will lose their protective variability. When you drive past a field of corn today, every stalk in it is identical to every other—not just extremely similar, but eerily, molecularly identical. Replicants live in perfect harmony since none can outcompete any others. But they also have matching vulnerabilities. In 1970, the corn world suffered a real fright when a disease called southern corn-leaf blight started killing corn across America and it was realized that practically the entire national crop was planted from seeds with genetically identical cytoplasm. Had the cytoplasm been directly affected or the disease proved more virulent, food scientists all over the world might now be scratching their heads over ears of teosinte and we would all be eating potato chips and ice cream that didn’t taste quite right.
Potatoes, the other great food crop of the New World, present an almost equally intriguing batch of mysteries. Potatoes are from the nightshade family, which is of course notoriously toxic, and in their wild state they are full of poisonous glycoalkaloids—the same stuff, at lower doses, that puts the zip in caffeine and nicotine. Making any wild potatoes safe to eat required reducing the glycoalkaloid content to between one-fifteenth and one-twentieth of its normal level. This raises a lot of questions, beginning most obviously with: How did they do it? And while they were doing it, how did they know they were doing it? How do you tell that the poison content has been reduced by, say, 20 percent or 35 percent or some other intermediate figure? How do you assess progress in such a process? Above all, how did they know that the whole exercise was worth the effort and that they would get a safe and nutritious foodstuff in the end?
Of course, a nontoxic potato might equally have mutated spontaneously, saving them generations of experimental selective breeding. But if so, how did they know that it had mutated and that out of all the poisonous wild potatoes around them here at last was one that was safe to eat?
The fact is, people in the ancient world were often doing things that are not just surprising but unfathomable.
III
While Mesoamericans were harvesting corn and potatoes (and avocados and tomatoes and beans and about a hundred other plants we would be desolate to be without now), people on the other side of the planet were building the first cities. These are no less mysterious and surprising.
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