Agriculture

We’ve been around for 100,000 years, more or less. That’s a hard number to visualize: let’s say 5,000 generations. That seems alike a long time especially if you figure that Julius Caesar lived only 100 generations ago – say, 2% of the way back.

For 90% of our collective existence we lived without agriculture. The commonest term for our economy during this time is “hunting and gathering” or “foraging”. (the latter includes the scavenging that must have taken place often).

The Kalahari, a vast, arid plain of dried rivers and salt pans, covers 100,000 sq. miles in the southern part of the African continent. Parts of the Kalahari receives <6” of annual rainfall, and even that little bit of precipitation is erratic and unpredictable. Daytime temperatures can avg. over 100F (38C), and severe and prolonged droughts are common. Soils are sandy and salty and completely unsuitable for cultivation. It’s a sparsely populated region; its lack of arable soil, low precipitation, and temperature extremes makes it as inhospitable a place for mass human dwellings as, say, another inhospitable region, the treeless tundra of Alaska.

Yet both areas have been successfully inhabited for thousands of years - not by agriculturalists, but by people who have depended on wild plants they gather (Kalahari) and the wild animals (seals, walruses, whales) they hunt. Because they rely on these wild sources of food, the 50,000 !Kung (San) peoples of the Kalahari, and the 28,000 Inuit of Alaska and the Aleutian Islands, are called hunter-gatherers.

Hunter-gatherer, is a term applied to those people that exist by gathering wild plants, fishing, hunting, and foraging for invertebrates. The few cultures left that solely rely on hunting and gathering for subsistence represent extremes on a cultural spectrum of mixtures of agriculture and wild harvesting. (Most societies that primarily focus on hunting also dabble in agriculture; most agrarian societies occasionally hunt and gather wild plants.)

H/G societies have been characterized by close family ties, an abundance of leisure time (so much so that anthropologist Marshall Sachlins refers to the !Kung San as “the original affluent society”, a remarkably sophisticated knowledge of indigenous plants; egalitarian societies; relatively small communities.

In one excavated site of hunter-gatherers in the Nile Valley of upper Egypt, dated 17,000-18,000 yrs ago, charred remains of fruit, seeds, and tubers of 25 different plant species were found, indicating early foraging people had a remarkably varied diet.

Many h/g people then, and now, had a thorough knowledge of the botany in their area. From experience they knew which plants were edible, which were nutritious, which plants were poisonous, which had medicinal value or psychoactive properties, which cd be used for dyes, which for weaving, and which for building materials. They had also developed methods to prepare foods that in their found state were toxic, such as cassava, which contains poisonous hydrocyanic acid (cyanide).

Looking at modern foragers like the !Kung San of the Kalahari, we can inductively construct what life may have been like for ancient foragers. Living in the tropical savannahs that border the Kalahari, in what is now southeastern Angola, northeastern Botswana, the !Kung have foraged this area for the last 10,000 yrs, continuing their h/g ways until very recently.

Studies of the !Kung revealed that they utilized over 100 spp of plants and 50 animal spp.; 2/3s of their diet was plant-based - fruit, nuts, berries, melons, roots, greens - consuming a nutritious diet with an average of 2,355 Calories per person per day, with 96 grams of protein and adequate vitamins and minerals.

Similarly, a pre-agricultural diet consisted of meat, fruits, nuts, legumes, edible roots, and tubers. Early farming was based primarly on wheat and barley, and most of their caloric intake was cereal-derived (as it is for most peoples today).

Characteristics of Foraging (hunting-gathering peoples)

1. The amount of time spent on foraging activities averaged only 2.5 days per week. (Simple horticulturalists of contemporary times spend about 3 hrs per day in food production and get less animal protein for their efforts than do the Bushmen. In rice-growing regions in eastern Java, workers spend up to 44 hours per week in productive farmwork, something no self-respecting Bushman wd do! And Javanese workers seldom eat animal protein. American farmers spend 50-60 hrs per week).

a. Less work for the same amount of food.

b. Development of farming leads, in part, to increased work load, per capita.

2. Egalitarianism - altho there were divisions of labor based upon gender, there wasn’t the economic stratification that developed after domestication of plants and animals: stratified labor, private property, security, etc. Leadership is less formal and more subject to constraints of popular opinion than in village societies governed by headmen and chiefs. Leadership by example, not by fiat; by persuasion, not by command. This aspect of their way of life allowed for a degree of freedom unheard of in more hierarchical societies, but has put them at a distinct disadvantage in their encounters with centrally organized colonial authorieties.

3. Resiliency/Mobility - it may be that H/G cultures were more resilient than agrarian societies in the face of environmental perturbation - they moved easily and were not reliant upon only a narrow base of plants (food). People tend to move their settlements frequently, several times a year or more, in search of food. This mobility is an important element of their politics. People in band societies tend to “vote with their feet”, moving away rather than submitting to the will of an unpopular leader. Mobility is also a means of resolving conflicts that would be more difficult for settled peoples.

4. Population size: Bound by the dictates of area’s carrying capacity. H/G must keep their population density relatively low to enjoy leisure and high quality diet; i.e. they must keep low pop. density in relation to their prey and edible plants ( the carrying capacity of their area). They often did not live in uniform sized groupings throughout the year, but tended to spend part of the year dispersed into small foraging units and another part of the year aggregated into much larger units.

a. The Innu would spend the winter dispersed in small foraging groups of 10-30, while in the summer they would aggregate in groups of up to 200-300 at a lake of river fishing site. This represents a dialectical interplay of social and ecological factors.

b. The same can be said about the Pygmie peoples (Aka, Baka, and Mbuti) and the nearby Bantu

c. Even in favorable habitats, H/G probably kept their pop densities to 1-2 persons/sq. mile.

Anthropologist Alfred Kroeber estimated that in Canadian prairies and plains the bison-hunting.

Cree, mounted on horses and equipped with rifles, kept pop densities below 2 persons/sq. mile.

d. Less-favored grps of hunters, the Nunamuit Eskimo, who depended on caribou, maintained densities below 0.3 people/sq. mile. The numbers of people per sq. mile is contingent upon the carrying capacity of the habitat; the availability of the natural resources.

5. Common property regime – land tenure system was based on a common property regime.

While movable property in held by individuals, land is held by a kinship-based collective.

So, about 10,000 years ago, groups of people in several areas around the world began to abandon the foraging lifestyle that had been successful, universal, and largely unchanged for millennia. They began to gather, then cultivate and settle around, patches of cereal grasses and to domesticate animals for meat, labor, skins, and milk.

Why was agriculture reinforced if it wasn’t offering adaptive rewards surpassing those accruing to hunter-gathering or foraging economies?

Until recently, the transition to farming was thought of in progressive terms: people learned the planting of seeds caused crops to grow, and this new, improved food source led to larger populations, sedentary farms, town life, specialization, more leisure time, writing art, technological advances, and civilization.

It is now clear that agriculture was adopted despite certain disadvantages of that lifestyle.

Advantage of food production

1. By selecting and growing species of plants that we eat, so that they contribute 90% of the biomass per acre of land, rather than 0.1%, we obtain far more edible calories per acre. Among wild plants and animals a relatively small minority are edible to humans or worth hunting and gathering. Some plants are indigestible (bark); some plants are poisonous (death cap mushrooms); some plants are low in nutritional value; some plants are tedious to prepare (small nuts); some foodstuffs are difficult to gather (larvae), and dangerous (lg. animals). Most vegetable biomass (living biological matter) on land is contained within wood and leaves - most of which is indigestible to us (lignin and cellulose).

2. Reliable food source and increased food supply and food surpluses.

3. Agriculture is a system of food production that can absorb much more labor per unit of land than can hunting or gathering. H/G are dependent upon the natural reproduction rates of animals and plants. They can do very little to raise output per unit of land (altho they can easily decrease it!).

With agriculture people control the rate of plant reproduction, and reproduction can be intensified without immediate adverse consequences.

Effects of sedentarianism (sedentary life style)

1. Fixed abode - denser human populations; shorter birthing intervals. H/G woman, who is shifting camp frequently can carry only 1 child at a time, along with a few possessions. She can’t afford to bear her next child until the first child can walk fast enough to keep up with the tribe. In practice, H/Gs space their children out ca. 4 yrs apart - by means of lactational amenorrhea, sexual abstinence, infanticide, and abortion. By contrast, sedentary peoples, unconstrained by carrying their young on frequent treks, can bear and raise as many children as they can feed. The birth interval for farm people is ca. 2 yrs., hald that of H/Gs. Increased birth rate of food producers + increased ability to feed people = increased population densities.

2. Food storage - fixed abode provides a reason and need to store and protect surplus that developed from increased food production. Food storage is essential for feeding non-producing specialists.

a. With stored surpluses, people were free to pursue activities not directly related to food production and survival. Social stratification.

b. Led to the concept of trade, currency, commerce, private property, security (protection), military.

c. Foragers of the deep past were too nomadic to store food. Instead, they cooperated in getting it, then shared it quickly before it spoiled.

d. With sedentary life and storage, families could be much more self-sufficient, and there was less need for cooperation and sharing.

3. Rise of civilization with its attendant:

a. Increased human population

b. Hierarchically organized societies (socio-economic classes, ob secialization, armies)

c. Arduous work oriented towards future pay-offs, and the demands of superiors. (Families no longer tended the land for themselves and their immediate needs alone, but for strangers and for the future).

Negative effects of sedentarianism (Diamond)

1. Health
1. From paleopathological techniques, archaeologists have been able to determine the health of ancient peoples based upon skeletal size, teeth, and fecal material.

i. Skeletons reveal the owner’s gender, height, weight, and approx. age. The average height of foragers in Greece and Turkey toward the end of the Ice Age (10,000 ys. ago) was about 5’9” for men, 5’5” for women. With the adoption of agriculture, heights crashed, and by 3,000 BCE had reached a low of 5’3” for men, 5’ for women.

ii. Enamel defects on teeth (indicating malnutrition), and bone scars (indicating anemia, tuberculosis, leprosy, and other diseases.)

iii. Fecal material indicated the presence of hookworm or other parasites.

iv. Early agriculturalists showed increased levels of enamel defects (malnutrition), anemia, bone lesions (infectious disease), and degenerative conditions of the spine (hard physical labor).

2. Hunter-gatherers enjoyed a varied diet, while early farmers obtained most of their food from one or a few starchy crops (cheap calories, poor nutrition). A growing reliance on very few crops. Hunter-gatherers didn’t survive on endless bowls of cereal and loaves of bread, but early farmers did, and still do in some parts of the world.

i. A diet based on corn accounted for severe nutritional deficiencies in the 20^th century among poorer populations of the American south: pellagra. Beriberi in the Orient from diets restricted to rice only).

3. Because of dependence on a limited number of crops, farmers ran the risk of starvation if one of the crops failed.
4. Agriculture encouraged people to clump together in crowded societies, leading to the spread of parasites and infectious disease. Epidemics couldn’t take hold in populations of scattered bands that constantly shifted camp, but could in the larger, settled life of the agrarians.

2. Class divisions and hierarchy
1. Agriculture provided the economic base for most hierarchical societies.
2. Surpluses and stored food brought with it the concept and practice of private ownership.
3. Private ownership led to discrepancies and stratification in the social order.

i. Skeletons from Greek tombs ca. 1500 BCE suggest that royals enjoyed a better diet than commoners, since royal skeletons were 2-3” taller, and had better teeth.

ii. Private ownership also lead to the need to protect what one thought was theirs: development of a military (army).

4. Inequality between the sexes.

i. Farming women tended to have more frequent pregnancies than their foraging counterparts, with consequent drains on their health.

ii. More women than men had bone lesions from infectious disease among Chilean mummies.

iii. Women were often made beasts of burden, carrying the heavy loads while men walked empty-handed.

Why did agriculture start?

1. Agriculture arose as a consequence of climate change (environmental determinist). V. Gordon Childe (1920s-1950s). After the Pleistocene (last glaciation) there was progressive desiccation. The resulting aridity brought about the withdrawal of humans, animals, and plants to banks of permanent rivers and oases. The close contact between humans, plants, and animals led to domestication (propinquity theory). Associated with domestication was the “Neolithic revolution”: sedentary village life, expanding population, use of ground stone tools, development of ceramics, and emergence of a new type of social organization.

2. Demographic pressure (stress) - Lewis Binford - an increase in population density led humans to attempt to manipulate the environment in order to increase food production. Depletion of natural resources.

3. Fishermen - Carl Sauer - cultivation of plants first arose amongst fishermen. They wd. have been more-or-less sedentary, and wd. have had a dependable source of food, giving them the time and stability to experiment with cultivation. Sedentary before food production.

4. Dump-heap theory - Edgar Anderson - in rubbish heaps and campsites, seeds might have been dropped, and parts of plants might have been discarded. Such refuse heaps, being rich in nitrogen, cd. have given rise to vigorous plants that were, in turn, used by people. Disturbed habitats wd. increase the chances of hybridization and therefore the production of new gene combinations subject to selection.

5. Cities - Jane Jacobs - cities gave rise to agriculture (a reversal of commonly accepted chronology / cause and effect) Early cities arose as trading centers and agriculture actually developed in them, and was later moved to outlying areas. Animals brought to cities for barter wd. have been kept alive until needed, which might be a first step toward their domestication.

6. Plant geography - Culberson - the beginnings of agriculture owes itself not solely to the native inventiveness of the practictioners, but rather to the fortuitous accidents of plant geography. Even tho there were originally enough gatherable food plants and huntable game for humans 35,000 yrs ago, the distribution of plant species with the right biological traits for domestication was immensely less universal. That had to wait until 11,000 yrs ago, in the Fertile Crescent area.

7. Exceptional individual theory - a wise old sage notices an especially vigorous or tasty plant and transplants it or sows its seed. In a flash of insight this sagacious person realized that if you sow seeds crops will emerge. This theory has many variants, including the dump-heap theory of plants growing at middens or “lavatories”, and graveyards (burial sites) where seeds buried along with the deceased person, gave rise to plants soon thereafter.

8. B. Hayden suggests that early cultigens and trade items had more prestige value than utility, and suggested that agriculture began because the powerful used its products for competitive feasting and accrual of wealth.

9. Cereal agriculture (Wadley and Martin): exorphins (opioids), cereals as both staples and drugs (with artificial rewards).

10. Religious (Hahn) - use of cattle and other animals as part of ritual sacrifice, either sacrifices to gods and goddesses, or as substitutes for humans (human sacrifice and killing having been very ancient customs). The same may be said for certain plants. Anderson (1954) nominated amaranths a candidates for ritual domestication.

What tipped the scales in favor of agriculture?

1. Decline in available foods (wild). Over-hunting, over-collecting. Lifestyle of H/G has become increasingly less rewarding over the past 13,000 yrs as resources they depended on have become less abundant, or have disappeared. As plants and animals become less available, there is greater effort to control the populations thru planting and domestication of animals.

2. Increased availability of domesticable wild plants (climate changes). Climate changes at the end of the Pleistocene (10,000 yrs ago) in Fertile Crescent greatly expanded areas of habitat with wild cereals, in which huge crops cd be harvested in relatively short time. Those wild cereal harvests were the precursors to domestication of earliest crops, wheat and barley.

3. Development of technologies upon which food production depended. Technologies for collecting, processing, and storing wild foods. These method, implements, and facilities developed in the Fertile Crescent 11,000 yrs ago as a way of dealing with the newly available abundance of wild cereal.

Inventions included flint blade sickles cemented into bone handles, used for harvesting wild grain; baskets of local grasses and stems and bark to carry home grain from hillsides where they grew; mortars and pestles or grinding slabs to remove husks of grains; techniques of roasting grains so they cd be stored without sprouting or rotting; underground storage pits.

4. Autocatalytic process: increased food production led to increased population density led to increased food production which led to increased population density. Positive feedback process, going faster and faster. With an abundance of wild grain, there was a gradual rise in pop densities, compelling people to obtain more food; once food production began, people became increasingly more sedentary; as they became more sedentary, their birth intervals became shorter, and they cd produce more people, who needed to obtain still more food.

5. Displacement of H/G by early agrarians with their larger numbers and superior weapons. Denser pop of food producers enabled a people to kill or displace H/Gs by their sheer numbers, in addition to associated advantages from food production. This was especially prevalent at geographic boundaries between H/Gs and food producers. In most areas of the world where food production is suitable, H/Gs met 1 or 2 fates: either they were displaced by neighboring food producers, or they survived by becoming food producers themselves.

Only where there was a potent or formidable geographic or ecological barrier - making immigration of food producers or diffusion of locally appropriate food producing techniques difficult - were H/Gs able to persist until modern times in areas suitable for food production. E.g. Native American H/Gs of California were separated from Native American farmers of Arizona by the Mojave Desert. The Australian Aborigine H/Gs were separated from food producers of New Guinea and Indonesia by portions of the Pacific Ocean.

The few peoples who have remained H/Gs in the 20^th century, escaped displacement by food producers because they are confined to areas unsuitable for food production - especially the deserts and the Arctic.

6. Domestication of animals for meat, milk, fertilizer, and work (plow).

Meat - domestic animals replaced wild game as major source of protein. Cows, pigs, sheep, and chicken, rather than deer (venison).

Milk - lg. mammals served as source of milk and milk products - butter, cheese, yoghurt. Milked animals included cow, sheep, goat, horse, reindeer, water buffalo, yak, Arabian and Bactrian camels. Mammals yielded several times more calories over lifetime when milked rather than just slaughtering them to consume as meat.

Fertilizer - crop yields are greatly increased with additions of manure as fertilizer. Even with modern availability of synthetic fertilizers, most societies today still use animal manure, esp. cows, but also yaks and sheep. Manure is also valuable source of fuel for fire in traditional societies.

Sites of Early Agriculture

Archaeological excavations have documented many sites of early agriculture in both the Old and New Worlds. It is thought now, by many, that agriculture has arisen, independently, in at least 5 areas of the world:

1. Southwest Asia (Near East, Fertile Crescent, Mesopotamia): includes Iraq, Iran, turkey, Israel, Syria,

2. China (includes Southeast Asia, Korea and Japan).

3. Mesoamerica (Central and Southern Mexico and adjacent areas of Central America)

4. Andes and Amazonia (from Colombia to Peru)

5. Eastern United States

Independently refers to those areas where food production arose (domestication of indigenous crops) before the arrival of any crops (or animals) from other areas. Each one of these locations, domesticated different plants and animals at different times in the course of history.

Southwest Asia - wheat, peas, olives, figs, alfalfa; sheep, goats; 8,500 BCE

China - rice, millet, soybeans, apricots, tea, oranges, hemp; pig, silkworm; 7,500 BCE

Mesoamerica - corn, beans, squash, avocado; turkey; 3,500 BCE

Andes/Amazonia - potato, manioc; llama, guinea pig; 3,500 BCE

Eastern United States - sunflower, goosefoot; no animals; 2,500 BCE

1. Southwestern Asia –
1. Some of the oldest sites of agriculture are in southwestern Asia, the area known as the Fertile Crescent, which today includes parts of Iraq, turkey, Syria, Labanon, and Israel.
2. Plant and animal remains have been dated back 9,000-14,000 yrs ago.
3. Early plant domesticates include wheat, barley, peas, lentils; dogs, goats, sheep.
4. Dates determined for flint sickles and grinding stones discovered there indicate that before 8,000 BCE humans had likely become collectors of wild grain. There is evidence that 1,000 yrs later they were cultivating grain and keeping domesticated animals. At the Jarmos site, in northeast Iraq, these domesticated remnants were mixed with bones of wild animals, snail shells, acorns, and pistachio nuts, indicating a gradual transition from hunting/gathering to agriculture.

2. Far East –
1. Among the earliest plants domesticated in the Far East are rice, millet, rape (mustard), hemp.
2. There is evidence of domesticated cattle, pigs, dogs, and poultry.
3. Recent excavations in China provide evidence that agriculture was established between 7-8,000 yrs ago in settlements along the Yellow River, and the lower reaches of the Yangtze River.

3. New World (Mesoamerica, North America, Andes)
1. Among earliest crops domesticated in New World were corn, squash, beans, chili peppers, amaranth, avocado, gourds, white and sweet potatoes;
2. Domesticated animals included dogs, turkeys, and llamas.
3. One of the most thoroughly studied sites is a group of caves in the Tehuacan Valley of central Mexico where research was initiated to obtain information on the ancestry of corn. Archaeologists have determined that corn was domesticated in this area about 5,500 yrs ago.

Centers of plant domestication - Within each area of the world where agriculture evolved, the native peoples developed indigenous crops for a staple food supply. Crops that were particularly suitable for agriculture slowly spread to surrounding regions as people traded with others or migrated to new areas, bringing their crops with them. This diffusion led to the emergence of principle crops associated with major centers of the world. Today many crops are more successful outside their native range than they were within it: Diffusion

a. Potatoes have become associated with Ireland but are actually native to the Andean highlands of Peru, where there are ca. 3,000 varieties of potatoes. They weren’t introduced into Ireland and England until 1590. The leading producers today are China, Russia, and Poland.

b. Coffee, so often linked with Colombia and Brazil, is native to the mountains of Ethiopia.

c. Tomatoes took their time before being accepted in Italy and the rest of southern Europe; they are native to the New World and the highlands of Mexico.

d. Corn (maize) originated in Mexico, but China grows 6 times as much corn, and the U.S. 10 times as much corn as Mexico.

e. Wheat originated in the Middle East but the largest producers today are China, India, and the U.S.

f. The leading cocoa producer is Ghana, not Mexico where it originated.

The person most often associated with pinpointing the exact origin of important crops (geography of diversity) is Nikolai Vavilov (major work, the 1^st quarter of the 20^th century), a Russian botanist/geneticist. Vavilov was a brilliant scientist, spoke at least 8 languages. “Life is short, we must hurry.”

He was arrested in August, 1940 by Soviet agents, for high crimes and treason: belonging to a rightest conspiracy, spying for England, and sabotage of agriculture. He was transferred to a prison camp in Sartov where he died, on January, 1943, of starvation. Of course, Vavilov’s real mistake was being a good scientist during times in which being a good scientist was bad politics. (20^th century: Hitler, Amin, Pol Pot, Mao, and Stalin). During the 1930s in Russia, genetics came under attack from a movement led by T.D. Lysenko, a Soviet biologist (somewhat akin to genetics coming under attack in U.S. by the Moral majority), who charged that genetics was a prop of secular humanism and, therefore, fascist and anti-Communist. Lysenko believed in the inheritance of acquired characteristics; that genes cd. be “trained”. He believed that spring wheat varieties cd. be coaxed into becoming winter wheat varieties and vice versa simply by exposing seed to soaking in water of different temperatures. It emphasized that traits acquired during life cd. be passed on to the next generation, which seemed consistent to Stalin’s view of historical materialism and the making, by the state environment, the “new man”. Lysenko’s “science” was politically acceptable, and he was in and Vavilov (a Mendellian) was out. A few yrs later, Russia suffered one of the worst famines in its history in which it is reported that millions of people died.

In Vavilov’s enormous travels and seed collections (quarter of a million entries to Soviet seed collection), he noticed a pattern of genetic variation - the diversity created by thousands of years of agriculture - was not equally distributed around the world. Some regions were blessed with astonishing diversity, while others were relatively impoverished. Vavilov reasoned that the degree of diversity was indicative of how long the crop had been grown in that area - the longer the crop had been grown, the more diversity it wd. display. He thought that by locating the center of diversity for a crop, one had pinpointed its origin (where a crop had originated with the time and opportunity to develop wide diversity). Observations by other scientists seemed to confirm Vavilov’s budding theory: while living in a suburb of Guadalajara, Mexico, Edgar Anderson noted that he found more variation in the corn grown in this one little township than in all the maize grown in the U.S.

Vavilov proposed 8 centers of origin for the major domesticated plants, 6 in the Old World, 2 in the New World. Recently, some of Vavilov’s assumptions and conclusions have been modified and refined - it is now believed that some crops have been domesticated more than once in different places; other’s didn’t originate where Vavilov thought they had; other crops had been domesticated independently in different areas; and highest diversity doesn’t necessarily indicate place of origin as some crops experienced their greatest variation/diversity in lands to which they were brought.

But the search for the origin of crops and their places of diversity is extremely important today as plant geneticists strive to improve the gene pool of domestic crops by tapping the genetic resources of wild ancestors.

Irish potato famine (1840s) - Phytophtora infestans (potato blight). Much of the potatoes planted in Ireland had a very narrow genetic range; they were almost all the same. They were not resistant to the disease, and their lack of resistance allowed the potato blight to reach epidemic proportions. Fortunatly, not all potatoes were vulnerable: among the thousands of varieties in the Andes and Mexico, resistance was located. Potatoes were the first crop in modern history to be devastated by lack of resistance - and the first crop to be rescued by the wealth of defenses built up over thousands of years in its center of diversity.

In the 1870s coffee rust essentially wiped out the coffee industry in Ceylon (now Sri Lanka), India, East Asia, and parts of Africa. As a result, England became a nation of tea drinkers.

In the early 1970s, corn blight struck the U.S. igniting concern over genetic uniformity in the nation’s crops.

Each time resistance was needed, and each time it was found in the crop’s center if diversity, in those landraces that somehow escaped homogenization, or in those crop’s wild relatives.