The Economist on wheat:

Economist.com : IN 10,000 years, the earth's population has doubled ten times, from less than 10m to more than six billion now and ten billion soon. Most of the calories that made that increase possible have come from three plants: maize, rice and wheat. The oldest, most widespread and until recently biggest of the three crops is wheat (see chart).... It is time to pay tribute to this strange little grass that has done so much for the human race. Strange is the word, for wheat is a genetic monster. A typical wheat variety is hexaploid.... It is derived from three wild ancestral species in two separate mergers. The first took place in the Levant 10,000 years ago, the second near the Caspian Sea 2,000 years later. The result was a plant with extra-large seeds incapable of dispersal in the wild, dependent entirely on people to sow them....

It happened first in the Karacadag Mountains in south-eastern Turkey—it is only here that wild einkorn grass contains the identical genetic fingerprint of modern domesticated wheat. Who first replanted the seeds and why? For a start, he was probably a she: women have primary responsibilities for plant gathering in hunter-gatherer societies. The time was certainly ripe for agriculture: the ability to make tools and control fire (cooking makes many plants more digestible) was already well established. But was it an act of inspiration or desperation? Did it perhaps happen by accident, as discarded grains germinated around human settlements?

The wheat plant evolved three new traits to suit its new servants: the seeds grew larger; the “rachis” which binds the seeds together became less brittle so whole ears of grass, rather than individual seeds, could be gathered; and the leaf-like glumes that covered each seed loosened, thus making the grains “free-threshing”. In the past two years, the very mutations that allowed these changes have been located within the wheat plant's genome.

Wheat's servants now became its slaves. Agriculture brought drudgery, subjugation and malnutrition, because unlike hunter-gatherers, farmers could eke out a living when times were bad. But at least that meant that they could survive. Population growth was now inevitable. Within a few generations, wheat farmers were on the march, displacing and overwhelming hunter-gatherers as they went.... Wherever they went, the farmers brought their habits: not just sowing, reaping and threshing, but baking, fermenting, owning, hoarding. By 9,000 years ago they had domesticated cattle, to which they could feed wheat to get meat and milk. They could also get precious manure to fertilise the fields. Not until 6,000 years ago did somebody invent the first plough to turn the earth, burying weeds and breaking up the seedbed....

The Malthusian crash was staved off in the 19th century by bringing more land under the plough—in North America, Argentina and Australia especially. But wheat yields per acre grew worse if anything as soil nutrients were depleted. So in 1898, in a speech to the British Association, a chemist, Sir William Crookes, argued again that worldwide starvation was inevitable within a generation. Population was rising fast. There was little new land to plough. Famines became worse each season, especially in Asia.

This time it was the tractor that averted Malthusian disaster. The first tractors had few advantages over the best horses, but they did not eat hay or oats. The replacement of draft animals by machines released about 25% more land for growing food for human consumption.... The only way to increase yield was to find a way of supplying extra nitrogen, phosphorus and potassium to the soil. Neither a break crop of legumes, nor manure was the answer, since both demanded precious acres to produce. The search for fertiliser took unexpected turns. British entrepreneurs scoured the old battlefields of Europe searching for phosphorus-rich bones. In about 1830 a magic ingredient was found: guano. On the dry seabird islands off the South American and South African coasts, immense deposits of bird droppings, rich in nitrogen and phosphorus, had accumulated over centuries. Guano mining became a profitable business, and a grim one. Off South-West Africa, the discovery in 1843 of the tiny island of Ichaboe, covered in 25 feet of penguin and gannet excrement, led to a guano rush followed by a mutiny and battles. By 1850, Ichaboe, minus 800,000 tonnes of guano, was deserted again....

On July 2nd 1909, with the help of an engineer named Carl Bosch from the BASF company, Fritz Haber succeeded in combining nitrogen (from the air) with hydrogen (from coal) to make ammonia. In a few short years, BASF had scaled up the process to factory size and the sky could be mined for nitrogen. Today nearly half the nitrogen atoms in the proteins of an average human being's body came at some time or another through an ammonia factory....

[A] man named Norman Borlaug was breeding fungus-resistant wheat for a project funded by the Rockefeller Foundation. Borlaug took some... seeds to Mexico and began to grow new crosses. Within a few short years he had produced wheat that yielded three times as much as before. By 1963 95% of Mexico's wheat was Borlaug's variety, and the country's wheat harvest was six times what it had been when Borlaug set foot in the country. In 1961 Borlaug was invited to visit India by M. S. Swaminathan, adviser to the Indian minister of agriculture. India was on the brink of mass famine.... After an epiphany in a taxi in a crowded Delhi street, the environmentalist Paul Ehrlich wrote a best-seller arguing that the world had “too many people”. Not only could America not save India; it should not save India. Mass starvation was inevitable, and not just for India, but for the world.

Borlaug refused to be so pessimistic. He arrived in India in March 1963 and began testing three new varieties of Mexican wheat.... [T]he state grain monopolies lost their power to block the spread of Borlaug's wheat. Eager farmers took it up with astonishing results. By 1974, India wheat production had tripled and India was self-sufficient in food; it has never faced a famine since. In 1970 Norman Borlaug was awarded the Nobel Peace Prize for firing the first shot in what came to be called the “green revolution”....

Soon after Norman Borlaug went to India in 1963, a remarkable thing began to happen. The world population growth rate... stopped rising. And by 1974 it was falling significantly.... Demographers, who had been watching the exponential rise with alarm, now forecast that the population will peak below ten billion—ten gigapeople—not long after 2050.... This is an extraordinary development, unexpected, undeserved.... In 10,000 years the population has doubled at least ten times. Yet suddenly the doubling has ceased. It will never double again. The end of humanity's population boom will happen in the lifetimes of people alive today. It is the moment when Malthus was wrong for the last time.

Of course feeding ten billion will not be trivial. It will require at least 35% more calories than the world's farmers grow today, probably much more if a growing proportion of those ten billion are to have meat more than once a month. (It takes ten calories of wheat to produce one calorie of meat.) That will mean either better yields or less rainforest—which is why fertilisers, pesticides and transgenes are the best possible protectors of the planet. The story of wheat is not finished yet.