The Big Ratchet: How Humanity Thrives in the Face of Natural Crisis (19 page)

The first half of the twentieth century put modern agriculture on the road toward a fossil-fuel-dependent strategy. The problem created by that solution is well known. The impact on the atmosphere is turning out to be one of the premier scientific and political
issues of the twenty-first century. Burning fossil fuel spews the greenhouse gas carbon dioxide into the air to short-circuit the long grind of the planet’s recycling machinery. The Swedish Nobel laureate Svante Arrhenius saw early on the dangers of this unintended by-product from an otherwise clever idea to twist energy from ancient sunshine. In his prescient 1896 paper, entitled “On the Influence of Carbonic Acid in the Air upon the Temperature on the Ground,” he speculated that variations in the amount of carbon dioxide in the air could contribute to variations in climate, a fact of physics that
today is without doubt.

The planet has seen wild swings in climate before, so the problem is not so much what it does to the planet as what it does to us. Rising temperatures, flooding coastlines, storms, and shifts in weather patterns from the human acceleration of the carbon cycle cause havoc for farmers and city-dwellers alike. All aspects of human civilization—from where people reside on vulnerable coastlines to the ways they grow food—developed in the stable Holocene climate of the past 10,000 years. Unpredictable fluctuations are hard for us to deal with, as they may have been for the other, now extinct species in the human family over the long course of human evolution, and for the numerous collapsed societies, from the
ancient Maya to the Norse of Greenland. In the geopolitical realm, President Franklin Roosevelt’s 1938 warning about the dangers of concentrating critical phosphate deposits in the hands of a few reverberates even louder with modern civilization’s utter dependence on coal seams and oil deposits.

In the century between Malthus’s prediction of impending crises and Crookes’s extrapolation that wheat would be insufficient to feed the
civilized world, the path was set for a major pivot point in civilization’s interface with nature. Instead of shortages and famine, the pivots broke open the bottlenecks for nutrients to keep soils fertile and for new sources of energy to supplement human and animal labor on the farm. Many factors drove the ratcheting facility of our species to manipulate the planetary machinery—among them fear of shortages, prospects of profits, discovery of geologic quirks, and intellectual curiosity. The solutions themselves spread through many routes, from secrets sold to the highest bidder to competition for patents and repurposed war-era capacity. As Roosevelt foresaw, the industrialized world’s food supply became shackled to fertilizer factories, mines scattered around the world, and oil wells in the hands of a few. The by-products of abundance for fouled lakes, soiled coastlines, and the atmosphere were destined to affect many people in many places around the world.

With constraints lifted in the early twentieth century on two of the conundrums of settled life—soil fertility and returns on investments of human energy—one twist of nature remained before the Big Ratchet could go full swing. It’s the same one that first set off the transition from forager to farmer long ago. Once the chemistry of lifeless inputs was in place to harness nitrogen gas in the air, phosphate rocks in the ground, and fossil fuels from the earth, the next pivot came once again from biology. Our species’ stamp on the world again grew larger with more ways to manipulate genes.

Printed with permission of John Chase

“Brother Mendel! We grow tired of peas!”

7: MONOCULTURES MARCH ACROSS THE MIDWEST

A
S INGENIOUS AS THE EARLY PLANT BREEDERS WERE
thousands of years ago, they did not have many options for exerting their influence over natural selection. They could collect the seeds of plants with the traits they wanted—larger or softer edible seeds, seeds that stayed on the stem longer, fewer spines or bristles—and hope those seeds would yield progeny with those same traits. Sometimes it would work and sometimes it wouldn’t. Over many trials, eventually more plants would acquire the desired traits, but it took a long time and hundreds of plant generations. They were stacking the deck by selecting the plants, but they were still playing with wild cards and the randomness of inheritance. For millennia, people could breed new varieties of domesticated plants and animals to suit their tastes, but only through repeated trials to sort out the good from the bad. It took more than a little patience. The outcome was not predictable, and the mechanism underlying the process was an enigma.

Scholars disagree on whether Charles Darwin got his brilliant mid-nineteenth-century insights into natural selection by analogy to
human’s artificial breeding of dogs, pigeons, sheep, and horses, or realized only afterward that artificial
breeding is like natural selection. Either way, he argued in his famous book
On the Origin of Species
that the process is similar. Nature selects the traits that improve chances of survival in the wild, and humans select traits they find desirable. The dice are then loaded in favor of the progeny inheriting the trait, but there’s still plenty of variability in the outcome. Darwin gave nature better odds than people: “How fleeting are the wishes and efforts of man! How short his time! And consequently how poor will his products be, compared with those accumulated by nature during
whole geological periods.” But the vagaries of inheritance left Darwin puzzled. He admitted in the first chapter of his book that “the laws governing inheritance are quite unknown; no one can say why the same peculiarity in different individuals of the same species, and in individuals of different species, is sometimes inherited and sometimes not so; why the child often reverts in certain characters to its grandfather or grandmother or other
much more remote ancestor.”

Although Darwin was at a loss to explain the genetic mechanics of why natural selection occurs, he made two critical observations that rippled into the ratcheting food production of the following century. These principles are pithily summarized in the title of one chapter in the
Origin of Species
: “On the Good Effects of Crossing, and on the Evil
Effects of Close Interbreeding.” Both conclusions resulted from experiments with plants in his greenhouse. First he discovered the evils of inbreeding: closely related parents produced less hardy progeny. This conclusion gave him great distress, as Darwin had married his first cousin, Emma Wedgwood. Although this was not unusual for the times, he worried that the same inbreeding effects he saw in plants applied to his offspring as well. “I have now six Boys!! & two girls; & it is the great drawback to my happiness, that they are not very robust,” he
wrote to a friend in 1858. Indeed, three of his ten children died in
childhood, including his beloved daughter Anne, who died at the age of ten, most likely of tuberculosis. Darwin had cause to worry; recent analyses of the Darwin and Wedgwood family trees have confirmed that his fears of
inbreeding were well founded.

Darwin’s second conclusion had less personal importance but colossal practical ramifications, as it formed the basis for hybrid seeds, one of the major pivots of twentieth-century agriculture. “I have collected so large a body of facts, showing, in accordance with the almost universal belief of breeders, that with animals and plants a cross between different varieties, or between individuals of the same variety but of another strain, gives vigor and fertility
to the offspring,” he wrote. Darwin had hit upon the principle of hybrid vigor, the truth that offspring from parents of different varieties—whether corn, cows, or dogs—grow faster and are generally more robust and healthy than those bred from
parents of the same variety.

Only a few years after Darwin published
On the Origin of Species
, the devout Austrian monk Gregor Mendel began his eight-year experiment with the common pea in the monastery’s garden. Although he was a brilliant student, Mendel’s upbringing in a poor peasant family in what is now the Czech Republic had left him struggling to make ends meet while pursuing his studies. When he joined the priesthood, he was so shy and his health was so poor that he could not take on pastoral duties. Instead he taught high-school mathematics and Latin, and carried out
his painstaking experiments.

The notion of the day was that plants and animals inherited their traits as a blend from both parents. Mendel intended to find out if this was truly the case, using pea plants as his test bed. He chose the pea for his experiment for good reason. Normally, the pea plant fertilizes itself, as the pollen it produces typically has no means of escaping its closed flower. Mendel could control fertilization by opening the flower, extracting the pollen with forceps, and dusting it on another
flower. The result was absolute certainty about the lineage of each generation of each plant. The pea provided Mendel with easily observable characteristics, among them whether the plant produced round or wrinkled peas, green or yellow pods,
and long or short stems.

Despite the pea’s fairly ideal attributes, Mendel still had substantial preparatory work to do before he could start his experiment in earnest. He first had to make sure he knew which characteristics the pollen and the eggs were passing on to their offspring. After two years and many generations of cross-fertilized plants, he was confident that he had “true breeds,” plants that would only produce offspring with the same characteristic as the parents. Once he had his true breeds, he began his cross-fertilizing experiments. He crossed plants with round peas with those with wrinkled peas, green pods with yellow pods, long stems with short stems, and so on for other characteristics. By the end, he had cross-fertilized thousands of plants.

Mendel found something remarkable in the cross-bred hybrids: all the peas crossed from round and wrinkled true breeds were round; all the pods crossed from green- and yellow-podded true breeds were green; and all the stems from the crossing of short- and long-stemmed true breeds were long. The hybrids were not blends, with half-wrinkled peas, green-yellow pods, or medium-length stems. He labeled round peas, green pods, and long stems as dominant characteristics. Despite the novelty of the result, he didn’t stop there. The genius of the experiment was that he continued for another generation of plants, in which he allowed hybrids to fertilize themselves as they would do in nature. The result was that some offspring came out round and some wrinkled, even though the pollen and eggs both came from plants with round peas. Some pods were green and some yellow. Some were long-stemmed and some short-stemmed. The ratio was constant. For every three round, one was wrinkled. For every three green, one was yellow. For every three long-stemmed, one was short-stemmed. The amateur biologist
had come upon the fundamental principle of dominant and recessive genes that all biology students study today.

Mendel hypothesized that each characteristic was the product of two discrete factors, one from the egg and one from the sperm in the pollen. Today we know these factors are genes. Combined with his theory of dominant traits, Mendel’s factors enabled him to explain the occurrence of traits in the second generation of his experimental pea plants. If, for example, in cross-fertilization the sperm passed on a green pod factor and the egg a yellow pod factor (which he was sure was the case because he had crossed only true breeds), then the dominant prevailed and the pod would look green. The pod would be yellow only if the sperm and egg both passed on the recessive, nondominant yellow factor. The first generation was all green because each hybrid intentionally received one green and one yellow factor. That meant the second generation still had a chance to get a yellow factor. In the self-fertilized second generation, the sperm and eggs had equal chances of passing on dominant green or recessive yellow. Only once in four times would the offspring’s pods
look yellow—only when it received a yellow factor from the sperm and a yellow factor from the egg. Another one in four would have been green, with two dominant green factors. Finally, two in four pods would have been green from the dominant factor, but with a mix of one green and one yellow factor. The outcome was the same for round and wrinkled peas and long and short stems.