Chapter: ORIGIN OF AGRICULTURE

By Thomas Dolezal

Developmental Biology Center, University of California, Irvine

 

harvest time in South-West Bohemia

 

 

 

FEW SPECIES DOMINATE THE TODAY'S WORLD

Estimates say our species alone uses forty percent of the primary productivity of the planet (see also Primary Productivity of the Earth in Chapter 16). That is, of all the solar energy converted into biochemical energy, almost half flows through our food chain – almost half to feed a single species among millions extant. Humans, few plants (mainly wheat, rice, corn, and potatoes) and members of the few domestic animal groups (cattle, chickens, goats, and sheep for the most part, and, as a special case, dogs) and the rodents, insects, weeds and disease parasites that come with them dominate the today’s world, while the millions of others ("non-coalition") creatures face extinction.

This was not a case just about ten thousand years ago (negligible period of time in a sense of biological evolution). Anthropologists believe the human species dates back at least 3 million years. For most of our history, these distant ancestors lived a precarious existence as hunters and gatherers. This way of life kept their total numbers small, probably less than 10 million on the whole planet. However, in last ten thousand years the Earth's population reached more than 6 billion with a tripling of the population during the lifetime of a today's older generation (see more in Chapter 16). Whereas the natural rate of extinction (ten thousand years ago for the last time) is estimated at about one species per year, the present rate is estimated at 10,000 times that - about one per hour!

It was origin of agriculture driving this enormous change. More than two thirds of today’s human nutrition comes from four crops: corn (maize), wheat, rice and potatoes. Each can be traced to a spot in the world where both agriculture and branch of civilization began: central Mexico, Middle East, Yangtze and Yellow River basins of China, Ganges plain of India, and Andes. Each produced a major urban civilization: Aztec, Western, Asian, and Inca.

What we are today - civilized, city-bound, overpopulated, literate, organized, wealthy, poor, diseased, conquered, and conquerors - is all rooted in the domestication of plants and animals. The advent of farming re-formed humanity (it is fundamental to our civilization), re-formed the whole world and is the cause why just few species dominate the today's world. As such, the origin and history of agriculture deserves deeper attention in the "Biodiversity and Conservation" class.

 

DOMESTICATION

There is evidence that hunter-gatherers routinely carried seeds with them. Nomadic Plains Indians, for example, enjoyed about as pure a form of hunter-gatherer culture as has been recorded, living almost exclusively off meat and following herds of bison. Yet they also grew tobacco. Tribes left contingents to spend the growing season stationed in a given river valley, minding the crop. We can call this proto-agriculture – practices that look like agriculture but do not cross the line to full-fledged cultivation. Domestication is human-driven evolution, a fundamental shift in which human selection exerts enough pressure on the wild plant that it is visibly and irreversibly changed, its genes altered.

The alteration of plants (and later animals) occurred at each of the key agricultural centers, but probably first in the Middle East, where a site along the Euphrates River shows clearly domesticated einkorn and emmer wheat and barley dating to 9,600 years ago:   

ORIGIN OF WHEAT

 

ORIGIN OF AGRICULTURE - HYPOTHESIS

We still don't have a widely agreed-upon explanation for why the agriculture occurred. Various hypotheses have been offered over last 50 years (more in Ecological Anthropology by Prof. Eric A. Smith) :

1. Cultural Progress hypothesis is the oldest, assuming that once bio-culturally capable, humans would inevitably develop agriculture subsistence as part of culturally-mediated progress from simpler to more complex, from arduous nomadic life to comfortable sedentary one, from wild to more and more "civilized" or "settled" state.

We know of cases where foragers are long-term neighbors of agriculturalists, and thus have access to both knowledge and domesticates, yet maintain their reliance on foraging. Thus foragers needed motivation to develop or adopt agriculture more than they need knowledge. Progress model assumes that motivation is obvious: agriculture would be less work, more reliable, and more productive than foraging.

But as medical historian Mark Cohen presents in his book Health and the Rise of Civilization (some on-line resources here), evidence from both ethnographic descriptions of contemporary hunter-gatherers and the archaeological record indicates that both the quality and quantity of human diets have actually declined due to agriculture and civilization. Almost every locale's soil and water are deficient in one mineral or another, a fact that was not a problem for nomadic hunter-gatherers. By moving about and taking food from a variety of niches, they balanced one locale's deficiencies against another's excess. For example, paleopathologists who have studied skeletal remains of hunter-gatherers living in the diverse and productive systems of what is now central California found them "so healthy it is somewhat discouraging to work with them."

As Cohen puts it, "Even the poorest recorded hunter-gatherer group enjoys a caloric intake superior to that of impoverished contemporary urban populations. Prehistoric hunter-gatherers appear to have enjoyed richer environments and to have been better nourished than most subsequent populations (primitive and civilized alike)." We have built our images of human history too exclusively from the experiences of privileged classes and populations, and we have assumed too close a fit between technological advances and progress for individual lives.

2. Environmental change hypothesis also very popular in past, associates the origin of agriculture with the climate changes at the end of Pleistocene/early Holocene. However, present consensus seems to be that while climate change may be a factor in origins of agriculture (see also text further), it is not sufficient in itself to explain it. 

3. Population pressure hypothesis - most popular view in recent years. Basic idea of this hypothesis is that population growth forces foragers to adopt agriculture, because wild resources become so scarce that eventually farming is worth doing, assuming that agriculture has one real advantage over foraging - it can provide more food per unit land (though at higher labor cost per unit food yield, and often lower nutritional quality).

There is, however, certain problems with this hypothesis. For 3 million years, human species existed on this planet as hunter-gatherers and for all this time the style of living kept their total number small. There is no reason to think that humans were (at least at the end of Pleistocene) different from all other species in case of a basic biological rule regulating the population growth - more food resources = increase in population size, less food resources = decrease in population size.

In fact, recent studies of human reproduction and fertility shows how the hunter-gatherers population were well adapted to their way of life assuring the stable population size. In fact, this way of living provided (and in certain areas of the world still does) women with natural (unintentional) contraception. In the text of Emily Schultz and Robert Lavenda (The Consequences of Domestication and Sedentism), we can see how woman's pregnancies in the societies of foragers tend to be spaced at least three to four years apart because of the extended period of breastfeeding  (ovarian activity is suppressed in the breastfeeding mother). There are many reasons that nursing continues for three to four years in these societies. The foraging diet is high in protein, low in carbohydrates, and lacks soft foods easily digestible by very young infants.  In addition to the effects of breastfeeding, age, nutritional status, energy balance, diet, and exercise all affect female fertility in a graduated way. In foraging societies, adding the caloric requirements of nursing to the physical demands of mobility, and the burden of food-gathering in the context of a high-protein, low-carbohydrate diet can keep the mother's energy balance low and thus decrease the overall fertility rate.

These studies also show how the invention of agriculture and sedentism (different physical activities) radically changed the factors influencing fertility. It meant shortening the period between pregnancies due to the dramatic change in diet (towards high-caloric carbohydrate diet), also with invention of "soft food" available for much younger infants and thus much shorter nursing.

During the last ten thousand years (years of agriculture), population pressure was pushing people to enlarge the cropland and make the agriculture more effective, in other words to increase the production. in

The last really large-scale increase of agricultural production (although less due to the enlargement of the cropland and more due to increase in effectiveness of agriculture) happened during the twentieth century - green revolution (see further). So that is why it was natural for anthropologist to think about the origin of agriculture in the same way, i.e. as a reaction to population pressure.

In further text, we will see that agriculture did not arise from need so much as it did from relative abundance.

"The genesis of agriculture under duress is akin to a passenger accidentally falling out of an airplane and "inventing" a parachute in mid-air as he falls to save his life."

 

Here we get close to one essential question which might radically shape our view of the world:

Was it population growth which forced people to invent agriculture

which is actually the effect that we can see still today - population growth forces people to enlarge the cropland and make the agriculture more effective. This question also evokes other problem: Does the increase in crop production solve the problem of world hunger?

or

was it the invention of agriculture which led to population growth?

and is it still the reason why the population inevitably increases?

 

 

(interesting reading on this topic in Daniel Quinn's books)

 

4. Co-evolution is most recent major hypothesis about agricultural origins. Co-evolution hypothesis proposes that proximity of humans and certain "proto-domesticate" species would set in motion a process by which humans would modify environment of this species, favoring genetic changes that would make it reproduce better. These same changes would make this species more attractive as human resource, and in turn humans would be selected (via cultural evolution) or motivated (via rational choice) to modify their behavior so as to favor its propagation, because this would give them more food, and hence more offspring who in turn would continue the co-evolutionary interaction.

 

 

EARLY HISTORY OF AGRICULTURE

 

Richard Manning expands on the co-evolution hypothesis in his book Against the grain with a well-researched and thorough analysis. Manning recognizes at least three preconditions of agriculture:

1 Presence of candidates for domestication. Of all of the species of plant extant, only a tiny subset – a few hundred species – have readily edible parts. These are the candidates for domestication and agriculture began in the home range of those plants, because the plants’ evolution had already done most of the work – agriculture was simply opportunism. Agriculture probably happened in the Middle East first because the native wheat and barley were the easiest plants to domesticate.

2 A second precondition of agriculture is catastrophe. "By this," Manning writes, "I do not mean catastrophe in the human sense; hard times and starvation were not the necessities that mothered the invention of agriculture" (see also Population pressure hypothesis above). "In fact, something quit opposite happened. I mean catastrophe in the biological sense – a natural disaster, or something like one, that resets the biological clock to zero by wiping out an evolved suite of plant life, as happens after volcanoes, floods and fires." The creation of agriculture was very much dependent on fire and flood. Many domesticated plants are predisposed to grow in flood plains, where periodic inundation provides natural tillage that wipes out competitors. And slash-and-burn methods on which tropical agriculture has relied into modern times is nothing more than artificially induced catastrophe. The point of the fire is to reset the biological clock.

Biological succession. There is a very narrow range of colonizing plants designed by evolution to move in and restart the biological clock after catastrophe. Generally, they are annuals that don’t need to survive these harsh conditions year after year. They don’t need to persist, to set deep roots. Rather, they invest their resources in building large, easily detached, portable, long lasting seeds ready to exploit the next sweeping catastrophe. Once these colonizers gain a foothold and provide cover, shade, and organic matter in the soil, a more permanent community of plants dominated by perennials develops. This is the core process of biological succession, the natural maturation of communities. The colonizing annual’s strategy of investing its energy in seed doesn’t pay off in the mature community, because there is no unoccupied ground in which the seed can grow. The strategy disappears in mature conditions.

3 Quite the opposite to commonly accepted suggestion that it was the efficiency of agriculture that made settlement possible, stands the archeological evidence suggesting that sedentism was the third precondition of agriculture. The close relationship with disturbance, be it fire or flood, meant that agriculture could take its cue and its candidate species from naturally disturbed sites; but to ratchet up to farming would require a significant level of human disturbance. That is, it would require that people congregate in settlement, places where their activity would disturb the land, and more important, where people would stay long enough to plant and harvest. Sedentism, like flooding, requires a proximity to water. Particular groups of hunter-gatherers became skilled fishermen and settled in stable communities near river mouths. Their dependence on migration fish such as the salmon was particularly pronounced.

 

Agriculture did not arise from need so much as it did from relative abundance. People stayed put, had the leisure to experiment with plants, lived in coastal zones where floods gave them the model of and denizens of disturbance, built up permanent settlements that increasingly created disturbance, and were able to support a higher birthrate because of sedentism.

In the Middle East, this conjunction of forces occurred about ten thousand years ago, an interesting period from another angle. That date, the start of what is called the Neolithic Revolution, also coincides closely with the end of the last glaciation (fits well environmental change hypothesis above). When the glaciers retreated, catastrophic events were happening with increased frequency in floodplains around the world, especially in the Middle East.

1. Fire, Floods & Ice ®  Grain monoculture.  After natural catastrophes, hardy grains are often the first plants to reappear ...

2. Grain monoculture ®  Agriculture.   Man in areas victimized by these natural catastrophes merely 'discovered' this, and then by creating continuous 'catastrophes' (clearing land with fire, flooding land through irrigation) exploited nature's own regeneration mechanism, which we call 'agriculture'...

from Dave Pollard's synopsis

 

CONSEQUENCES OF CO-EVOLUTION

Our crowding and our proximity to a few species of domesticated animals "gave microorganisms the laboratory" they needed to develop more virulent, more enduring, and more portable configurations, and they are with us in this way today. At the same time, the ecological disturbance that was a precondition of agriculture opened an ever broadening niche, not just for our domesticated crops, but for a slew of wild plants that had been relegated to a narrow range. In all of this we can see the phenomenon called co-evolution. Species change to respond to change in other species. Coalitions form. Domestication was such a change. Life forms that co-evolved with man and grain monoculture included the rat, insect pests, weeds and parasites as well as the aforementioned diseases and a handful of animals suited to domestication, all of which thrive with monoculture.

In fact much of the 'conquering' of the hunter-gatherer world by 'civilized' man was really accomplished by our coalition partners: it was our diseases, to which hunter-gatherers had no exposure and hence no resistance, that killed most of them, not our weapons or their years of subsequent slave labor. The introduction of our domestic animals likewise altered the New World's terrain, since these animals had few natural predators and exploded in population, literally eating the natural flora to extinction.

Cattle in the New World. The unoccupied niche for big grazers was welcoming to two of catastrophic agriculture's most crucial and long-standing allies, cattle and sheep. Introductions by conquistadors in South and Central America and the southwestern United States in the sixteenth century brought cattle to temperate grasslands where they were well adapted to. So well were they adapted that they could propagate without human aid, so that when, for instance, Jesuits abandoned a mission on the pampas in 1638, the five thousand cattle left behind did not skip a beat. By 1700, there were an estimated forty-eight million feral cattle on the pampas, roughly equivalent to the number of bison on the Great Plains.

 

GREEN REVOLUTION

Previous spreading and long-term development of agriculture eventually led to usage of almost all easily-arable areas available on this planet and there was almost nowhere else to expand (besides marginal and forest land - see Chapter 10). By 1960 - the year standing as a halfway point in our population growth (the number of people reached 3 billion - half of today's 6 billion - Chapter 16), it was clear that agriculture's historical strategy of expansion was exhausted. What came next is commonly called the Green Revolution - the shift from increasing acreage to increasing yield allied with a number of developments.  The shift did not occur overnight, but only after a half century of warnings and catastrophic failings and first developments preceding this date.

The first root of the rapid increase in yields was hybridization - breeding unlike mates from different strains. The increase in yield by this way was especially remarkable for corn (unlike the human experience with wheat and rice, the process of domesticating maize was long and arduous). Hybrids accounted for about 1 percent of all corn planted in the US in 1933, and 50 percent only ten years after. Because hybrid does not pass to progeny, farmers could no longer save some of one year's crop to seed next year's. Producing seed became a separate business.

Another important factor was beginning of usage of chemical fertilizers and the first pesticides. Once farming ran out of arable land to devour, its consumption did not cease; technology simply enabled it to begin chewing up landscapes it had once been unable to digest, farming in effect began to claim oil fields, steel mines and phosphate mines. Interesting thoughts on this topic can be found in Richard Manning's essay published in Harpers magazine (The Oil We Eat).

 

SUMMARY

“The real problem is not to explain why some people were slow to adopt agriculture but why anybody took it up at all, when it is so obviously beastly."  (Colin Tudge of the London School of Economics)

 

Following table summarizes and compares (with great simplification, of course) two fundamentally different living styles - the one present for the most of the human kind history (more often called "prehistory") - the hunter-gatherers way of living, and the one which has overrun the former just in the last 10,000 years (what we are actually used to call "history") - the agriculture:

Way of life

hunter-gatherers

agriculturists

Nutritional quality

high

low*

Work

max. couple hours a day

eight or more hours a day

Efficiency energy spent per energy obtained from food

high

low

Diseases

developmental, genetic, (infectious)

developmental, genetic, infectious, nutritional and civilization

Ecological footprint

none or minimal

enormous

Productivity (yield per unit land)

less food per unit land

more food per unit land

Population

stable

increasing

  * half of the present world population is malnourished or have micronutrient deficiency (see World Hunger Facts 2004 and 12 Myths About Hunger)

 

 

Recommended reading:

Against the Grain : How Agriculture Has Hijacked Civilization

by Richard Manning, North Point Press, February 15, 2004

Health and the Rise of Civilization

by Mark Nathan Cohen, Yale University Press; Reprint edition August 1, 1991

(UCI library: WA 30 C678h 1989)

Trilogy by Daniel Quinn (Ishmael, Story of B, My Ishmael)

(some on-line sources here)

(UCI library: PS3567.U338 I8 1992)

Hunter-Gatherers : An Interdisciplinary Perspective (Biosocial Society Symposium Series)

by Catherine Panter-Brick, Cambridge University Press; (March 29, 2001)
(UCI library: GN388 .H865 2001)

Reproductive Ecology and Human Evolution (Evolutionary Foundations of Human Behavior)

by Peter Thorpe Ellison, Aldine; (December 1, 2001)

(UCI library: WQ 205 R428297 2001)