Agriculture, History of

Origins of Agriculture

The origin of agriculture was around ten thousand years ago or approximately four hundred human generations back in time and prehistory, before written records were kept. What is known is based on evidence gathered from archaeological sites. Agriculture started independently in at least three places in the world, each with a distinctive cluster of plants drawn from the local flora: Mesoamerica (Mexico/Guatemala: corn, beans, squash, papaya, tomatoes, chili, peppers), the Fertile Crescent (Middle East from the Nile Valley to the Tigris and Euphrates Rivers: wheat, barley, grapes, apples, figs, melons, lentils, dates), and north China (mid-reaches of the three-thousand-mile-long Yellow River: rice, soybeans, peaches, Chinese cabbages such as bok choy). From these regions and possibly others, notably Africa (sorghum, cowpeas, yams, oil palm), South America (potatoes, sweet potatoes, cassava, peanuts, pineapples), and a broad band of tropical southeast Asia (oranges, mangoes, bananas, coconuts, sugarcane), the invention of agricultures spread to encompass the entire world by two thousand years ago.

The history of agriculture is not that of a single technology to produce food, but of an array of methodologies. Planting seed broadcast across plowed fields typifies most cereals (50 percent of human calories). Vegetables, legumes, and corn are planted from seed in rows separated by furrows. Seed agriculture usually consists of annuals that are typically planted as genetically uniform monocultures. Agriculture of the humid tropics has been more vegeculture than seed-based. These vegetatively propagated crops are usually perennials, productive over the entire year and found in polycultures that tend to mimic the forest ecosystem.

The earliest agriculture of southeast Asia was typically based on roots and tubers such as yams and taro, tree crops such as coconut and banana, and perennials such as sugarcane. In the Americas, vegeculture developed with cassava, sweet potatoes, arrowroot, and peanuts, and moved up the eastern slopes of the Andes, ultimately domesticating the potato. These crops spread quickly throughout the world after European contact. Potatoes displaced wheat and barley in cold soils of northern Europe and bananas became the fruit of choice in the New World tropics.

Seed agriculture dominates where either a pronounced dry season or a frost results in a single crop per year. In south China rice is the summer crop, sweet potato the winter crop. In India rice is the monsoon crop, wheat the winter crop. Sometimes intercropping (different crops in alternate rows) and relay planting (starting the next crop before the previous one is harvested) are part of the multiple-crops-per-year cycle. Sequential cropping is where one crop follows another without seasonal fallowing, sometimes in double-cropping but more often in triple-cropping.

Fallowing is an important technology perfected in the Middle Ages as part of the crop rotation pattern. The first year a legume is planted and the soil is enriched by the nitrogen-fixing crop; the next year a cereal is planted. The third year the land is rested to regain soil moisture and restore soil health. This pattern approximates a natural ecosystem and is more sustainable over the long term than continuous cropping. The fallow crop rotation system maximizes resources but is not elastic enough to accommodate an increasing human population that has come to rely on continuous cropping or heavy use of inputs (such as fertilizer, pesticides, and irrigation) in single crop per year monocultures.

Ecologic Effects

Another theme is to measure the displacement of natural ecosystems of forest and grasslands by plowed cropland that supports an increasing human population. Only about five million people existed worldwide preagriculture, subsisting on hunting and gathering of wild animals and plants. Humans existed like any other wild animals in the biological world. Postagriculture, the human population grew slowly, but as people's mastery of food production technology developed (such as irrigation, weed control by hoe and plow, and planting crops in monocultures) and the number of crop plants increased, the world population climbed to an estimated 130 million people by the time of Christ, a twenty-five-fold increase from the Paleolithic pre-agriculture estimate. By 1650 the world population had reached a half billion, and half of these people were in settled urbanized villages, towns, and cities and not engaged in agriculture to produce their own food. All of the major food crops and domestic farm animals known today were known and used worldwide. The only significant crops added since 1650 are industrial crops such as rubber.

Since the middle of the nineteenth century the population has increased from one billion to six billion, an increase that would not have been possible without increases in agricultural yields. Through breeding, plus the use of fossil fuels to plant, fertilize, and protect crops, the average yield of all plants and productivity per unit area has increased ten-to fiftyfold. At present humans produce and consume over a twenty-year period as much food as was produced in the eight thousand years between the development of agriculture and the sixteenth century. Nonetheless, of the six billion people in the world, over one billion are estimated to be malnourished, and half of these are seriously underfed, mostly due to poverty and the diminished affordability of agricultural products. An estimated fifty thousand to eighty thousand starve to death or are fatally compromised each day—a majority are children, in part because they are growing rapidly and do not get enough essential materials such as vitamin A or quality protein.

Loss of Diversity

Another theme is to realize how few crops currently feed the human population, considering that preagriculture humankind subsisted on a list of approximately five thousand wild edible plants. The agricultural crop list is short. One-half of the plant calories people consume come from three grasses: rice, wheat, and corn.

Just over two dozen food plants account for 75 percent of all plant calories and 90 percent of arable land cultivated. This list includes six grasses: rice, wheat, corn, barley, oats, and sorghum; four legumes: soybeans, peanuts, common beans, and peas; two sugar crops: sugarcane and sugar beets; two tropical tree crops: bananas and coconuts; four starchy roots: potatoes, sweet potatoes, cassava, and yams; five fruits: tomatoes, grapes, apples, oranges, and mangoes; and two vegetables: cabbages and onions. These twenty-five crops literally stand between subsistence and starvation for the human population. This is an agricultural calorie list and does not recognize the extremely rich vitamin and mineral sources found in low-calorie vegetables and fruits. Also this list does not recognize the important regional foods of the world. For instance, the native American crop cranberries is extremely important to Americans at Thanksgiving but is insignificant on the world calorie chart (less than one-millionth of 1 percent).

Selection and Breeding

A dominant theme in the history of agriculture has been crop improvement and yield advancement through selection and exploitation of genetic diversity within the species and its close relatives. And now, there is bioengineering where a gene can come from anywhere in the biological world (genetically modified crops). The earliest stages of domesticated crops were probably not much more productive than the wild progenitors, but the act of cultivation and saving the seed to replant was a radical break with the past. Human selection (artificial selection) was replacing natural selection in shaping the plant. Traits associated with the domestication process are seeds and fruits that remain attached to the plant (nonbrittle rachis and nondehiscent fruits) and do not self sow. Another trait is larger fruits and seeds and less nondigestible fiber in seed coats and woody fibers (cellulose) in the fruits. This increases the palatability of these structures but leaves the plant less protected to insect or rodent predation, so that humans had to take greater care in postharvest storage. When humans planted the seed, they set in motion many selection forces that characterize domesticated plants: simultaneous and immediate germination on being sown in the ground; rapid and uniform growth; and a trend toward annuality if biennial/perennial. Additionally, a shortened vegetative phase often resulted in increased reproductive effort, thus increasing yield and uniform flowering and ripening. Most of these traits would be harmful for a wild plant.

Once domesticated plants began to travel through human migration and conquest beyond their local area of genetic adaptation, a large amount of genetic variation was released by chance hybridization of diverse forms or freedom from constraints (such as pests, pathogens, frost, and day length) of the old habitat. Citrus, for instance, was brought from East India to Spain by the Arabs, then taken to the West Indies by Europeans after Columbus. One mutant form gave rise to grapefruit, while a mutant orange in Brazil was the origin of the familiar navel orange.

The Columbian Exchange (New World plants to the Old World and vice versa) in the sixteenth century was the single most dramatic migration and acclimatization of crops throughout the world. Coupled with hybridization between dissimilar species, introductions of a tremendous number of new forms were generated. Examples are the potato from Peru, which conquered north Europe as a food plant displacing wheat/barley and turnips/peas; and tomatoes from Mexico, which were embraced in Italian cooking.

Recent yield improvement traces back to the rediscovery of Austrian botanist Gregor Mendel's (1822-1884) classic experiments on the heredity of garden peas. For the first time the plant breeding community had a set of principles by which to proceed with the crop improvement process. Products of this era are hybrid corn, changes in the photoperiod response of soybeans, and the dwarf-stature wheat from the International Center for the Improvement of Wheat and Corn (in Mexico) and rice from the International Rice Research Institute (in the Philippines). These late 1960s Green Revolution cereals and the genes they hold (dwarf stature and fertilizer responsive) now enter the food supply of three billion plus people and are directly responsible for feeding more than eight hundred million people by their increased yield alone. Never in world history had there been such a dramatic yield take-off as the Green Revolution. The hope is that the new and developing biotechnologies will have a comparable favorable outcome for global agriculture.

The irony of using elite improved varieties and commercial seed is that they have a tendency to eliminate the resources upon which they are based and from which they have been derived. Current elite varieties yield better than their parents and they displace them from farmers' fields. Once a displaced variety is no longer planted, its genes are lost to future generations unless it is conserved, usually in a seed bank collection or as a heirloom variety. The saving of old folk varieties, farmer landraces and garden seed passed down through a family, maintaining them in home gardens, has become increasingly widespread. Many of these heirloom varieties taste better, cook better, or possess other unique characteristics that set them apart, but they lack the productivity mechanized farming demands in modern agriculture.

SEE ALSO AGRICULTURE, MODERN; AGRICULTURE, ORGANIC; AGRONOMIST; GREEN REVOLUTION; SEED PRESERVATION; SEEDS; VAVILOV, N. I.

Garrison Wilkes

Bibliography

Harlan, Jack R. The Living Fields: Our Agricultural Heritage. Cambridge, UK: Cambridge University Press, 1995.

Harris, Donald, and G. C. Hillman, eds. Foraging and Farming: The Evolution of Plant Exploitation. London: Unwin Hyman, 1989.

Heiser, Charles B., Jr. Seeds to Civilization: The Story of Food. Cambridge, MA: Harvard University Press, 1990.

Janick, Jules, Robert Schery, Frank W. Woods, and Vernon W. Ruttan. Plant Science: Growth, Development and Utilization of Cultivated Plants. San Francisco: W. H. Freeman, 1981.