Mendel in the Kitchen A Scientist's View of Genetically Modified Foods (2004) / Chapter Skim
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2 The Wild and the Sown
2 The Wild and the Sown
Pages 23-46
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From page 23... ...
Parmentier disagreed. He persuaded Queen Marie Antoinette to put potato flowers in her posies to rehabilitate the image of the poor plant.
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From page 24... ...
A Jesuit priest wrote in 1590,"The main benefit of this cacao is a beverage which they make called Chocolate, which is a crazy thing valued in that country. It disgusts those who are not used to it, for it has a foam on top, or a scum-like bubbling." Likewise, in 1674 a group of Englishwomen described coffee, in a petition to government to ban coffee shops, as "base, black, thick, nasty, bitter, stinking, nauseous puddle water." Just as they were chary of trying new foods, Europeans clung to the old ones when they emigrated to America.
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From page 25... ...
The Wampanoag of Massachusetts burned the forest underbrush each year to make it easier to find and follow game. In California, according to Florence Shipak of the University of Wisconsin-Parkside, the Kumeyaay harvested the grains of wild grasses, then burned the fields; after the autumn rains, they broadcast some of the harvested grain, along with seeds of green, leafy plants and other vegetables that would ripen at the same time.
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From page 26... ...
The change most convincing to an archeaologist is in how the spikelet holding the seed or grain attaches to the stalk. In wild wheat the spikelets shatter easily so that a light breeze can scatter the ripe seeds onto the ground.
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From page 27... ...
Harlan describes them. Arrow-shaped, these spikelets "work their way into the soil, often aided by rough awns that vibrate in the wind." Once buried, the bristles have another function: the seed cannot germinate until the hull is broken down.
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From page 28... ...
Because the resulting hybrid, emmer wheat, had more chromosomes than either of its parent types, it could not breed with either one: it was an entirely new species. Emmer wheat is known by the species name Triticum turgidum.
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From page 29... ...
The most ancient variety of bread wheat is spelt. Jack Harlan, who made a career of studying crop evolution, believed that the original cross between emmer wheat and goat grass to produce spelt happened near the southern end of the Caspian Sea shortly after emmer wheat itself was domesticated.
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From page 30... ...
The difference between arable farming and other ways of encouraging plants to grow is plowing: the farmer breaks the soil, uproots all other vegetation, and sows the seed in bare dirt. There, protected from pests and predators, watered and weeded, a hybrid is at no disadvantage -- provided it looks like the crop the farmer intended.
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From page 31... ...
Gordon Hillman and Stuart Davis of University College London experimented with planting wild wheat on the scale they thought the first farmers might have used, then calculated how long it would take for domestic wheat to appear. By domestic they meant a mutant with a seed spikelet that did not shatter in a breeze.
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From page 32... ...
Corn, or maize, known to science as Zea mays, may be the greatest feat of genetic engineering yet. While domesticating einkorn wheat took a "few simple changes," in the words of Jared Diamond, creating corn seems to have required a "drastic biological reorganization." Like wheat, corn depends on humans to sow its seeds, stuck tight as they are on its enormous ears, which themselves remain firmly attached to the stalk.
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From page 33... ...
The Wild and the Sown 33 Corn and its ancestor, teosinte in 1919. Following the advice of Edward Palmer, an ethnobotanist at Harvard's Peabody Museum, Collins collected teosinte on the banks of an irrigation ditch in Durango, Mexico.
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From page 34... ...
From Edmund M East, Mangelsdorf's thesis advisor at Harvard University, they borrowed the idea that maize evolved from an extinct South American species.
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From page 35... ...
In 1971 he organized a teosinte hunt in Mexico to look for more wild maize relatives. Some of the teosinte seeds he collected on that expedition, from the Balsas River valley, found their way to John Doebley, now at the University of Wisconsin-Madison.
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From page 36... ...
To make a copy, the long twisting DNA double helix is first unwound: from resembling a spiral staircase, it begins to look much more like a ladder. Then the rungs of the ladder, each made of two linked bases, are separated.A new partner is found for each base until there are two copies of the original DNA.
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From page 37... ...
The hardness, size, and curvature of the glume, Doebley and his colleagues found, is controlled by a gene named teosinte glume architecture, or tga1. (Genes are often named for the way a mutation in the gene affects the plant.
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From page 38... ...
To these early farmers, the change to softer seeds probably just reduced the amount of work it took to make the seeds edible. Hugh Iltis, on the other hand, has suggested that teosinte plants were cultivated at first because their stalks are sweet, much like sugar cane, and that it was the tga1 mutation that first made the seeds useful as human food.
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From page 39... ...
Based on how frequently these differences arise, scientists can create a molecular clock. Using a molecular clock for maize, Brandon Gaut and his colleagues, then at Rutgers University, estimated how many generations and how many founding parents it would take to account for the variability in modern corn.
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From page 40... ...
If maize arose from different types of teosinte multiple times, we should be able to derive several family trees, tracing the domestication events back to the particular variety of teosinte that gave rise to each one. If it happened only once, all modern corn varieties should fit into a single family tree tracing back to a single teosinte ancestor.
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From page 41... ...
The Guila Naquitz Cave is in southern Mexico, 400 to 500 kilometers east of the Balsas River area where corn's closest teosinte relative lives today. The age of these earliest cobs pushes the origins of corn back to well within the estimate arrived at by the molecular biologists.
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From page 42... ...
. whom wheat cleverly exploited to spread itself around the world."Yet world dominance for wheat and corn came at a cost: domestication meant that each plant would henceforth and forever be a ward of humans, dependent on them for its survival -- just as human societies soon became dependent on their crops.
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From page 43... ...
And if the birth rate can exceed the death rate, even a poorly nourished people can multiply. As Diamond remarks,"Some productive hunter-gatherer societies reached the organizational level of chiefdoms, but none reached the level of states: all states nourish their citizens by food production." He adds, "Food production was indirectly a prerequisite for guns, germs, and steel.
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From page 44... ...
Both wild and domesticated potatoes contain bitter chemicals called glycoalkaloids which can reach toxic levels. "In the cultivated potato," Jack Harlan writes, "strains have been selected that are relatively safe, but even today, in areas far removed from the Andes, certain clones under some conditions can be dangerous." In the potato's homeland the problem is more acute."In the Andes, strains selected for low toxicity often cross with wild and weedy races and toxic tubers are produced: the local people must somehow live with the poisons." Many of them use an elaborate freeze-drying technique to get rid of the toxins.
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From page 45... ...
Because they came from a high altitude but a low latitude, writes plant physiologist Lloyd Evans,"andigena potatoes were well adapted to the cool conditions but not to the long days of European summers. Although it was not understood at the time, the long days of summer prevented tuber formation until close to the autumn equinox, leaving little time for tuber growth."It took 250 years of selection by European gardeners and botanists -- who grew potatoes as ornamental bushes, beautiful but "savage-looking" with their hairy stems and blue-purple flowers -- before Parmentier had a plant he and his fellow Parisians could eat.
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