Origins Of Agriculture
I. Human evolution
It is generally agreed that modern humans evolved more than 50,000 ybp in Africa. Some evidence suggests it may have been even earlier, but who's quibbling about a few thousand years. From Africa, humans migrated to other areas of the globe and by 30,000 ybp had crossed the Bering Strait to North America.
II. Changes in Methods of Food Procurement
Early humans, like some current societies including the !Kung, depended on hunting and gathering to supply their food. Agriculture (the intentional planting of crops) originated 10 - 15,000 ybp. Thus, human cultural evolution has followed the general pattern: hunter/gathers à farmer
III. Consequences and Causes of Adopting an Agricultural Lifestyle
A variety of changes accompanied the adoption of the agricultural (farming) lifestyle. These include:
- increase in population
- more leisure time? (some have suggested farming provided more leisure time, but this is questionable because studies with !Kung and other hunter/gatherer societies show that they have plenty of leisure time)
- increase in sedentary lifestyle
- increase in civilization. Associated with this are increases in urbanization (associated with the sedentary lifestyle), art, science, writing.
- increase in warriors and warfare – as a result of needing to "protect" holdings
- increase in social stratification, such as ruling class, laborers, class system
- increased urban problems like crime and disease (due to ease of transmission of disease, sanitation problems, etc.)
- decreased knowledge of indigenous plants
- increased famine. This is the result of a decreased reliance on multiple food sources. Thus there is a decreased resilience to environmental perturbations. Less able to (i.e., hunter/gatherer societies reliant on a variety of foods are better able to survive when one food source fails). The Anasazi in Mesa Verde are a prime example. Evidence shows that a drought destroyed the major crop, maize, forcing them to abandon their settlements, etc.
- increased dietary diseases due to eating more calories, fat, and sodium, which in turn increases the incidence of "Western diseases" including coronary problems, diabetes and obesity. Example - Gary Nabhan has studied the River Pima in the American Southwest who show a very high incidence of diabetes and obesity which is likely the result of: (a) diet (Western foods have a high glycemic index); (b) increased caloric intake; (c) sedentary lifestyle. The ultimate cause is a mutation in a receptor protein for basal metabolic rate. Thus, the obesity is linked to genetics which is exacerbated by environmental concerns.
- increased dietary diseases due to eating fewer traditional foods that may act medicinally and protect the body. Example - Masai (Kenya/Tanzania) – diet is rich in cholesterol/fat yet they have very low levels of cholesterol in blood. But, when they move to urban areas, the cholesterol levels increase. Why? Presumably because of the way they prepare food. Traditionally, food is boiled with tree bark that may reduce cholesterol levels.
- increase in "food" energy available (eating lower on the food chain which means it is possible to support the caloric needs of more people. Less energy is "wasted" on conversion into animal meat)
IV. Causes or Consequences?
In some cases, the factors listed above (III) may be responsible (causal agents) for the change in lifestyle (from hunting/gathering to farming) while others are the consequences. It is not always easy to distinguish whether a factor is a causal agent or a consequence. Here are two examples:
A. Population Growth.
Consider the population increase associated with the switch to an agricultural lifestyle. Although we know that the switch to an agricultural lifestyle is always correlated with an increased population, did the increase in population stimulate the need to develop a more reliable and plentiful food source, or was the population increase the result of greater food availability that could support larger numbers of individuals?
B. Which came first – Agriculture or civilization?
Some have suggested that farming allowed leisure time, which in turn, fostered the development of civilization. In contrast, Charles Heiser (a famous ethnobotanist) and others suggest that farming required demanding, organized work habits that led to civilization. Heiser argues that agriculture and civilization arose not so much as a response to extra leisure time but because of the discipline required to plant seed, harvest, etc. Writing developed to keep records. He cites studies of the !Kung and hunter/gathers in the Kalahari Desert (Africa) who have an adequate, nutritious diet and leisure time.
V. Domestication vs. cultivation
- Cultivation/agriculture/farming – is the process of growing a plant to harvest. The amount of energy expended in this activity can be intense or minimal.
- Domestication – is the process of "taming" wild crops (animals) and deliberately manipulating them for our purposes. It is controlled by selective breeding (artificial selection). Reproduction of the species is controlled by humans. Domesticated plants and animals have a very close association with humans; in most cases, domesticated plants only survive in association with humans. For example, maize, tobacco, soybeans, and many other crops, don't occur in the wild. They only persist because we collect and save the seeds at the end of the growing season to plant the following season. Obviously, domestication follows cultivation and is a more specialized activity.
VI. Evidence to study the Origin of Agriculture.
Since we are studying past events we need some way to look through the "window" of time. This can be done by analyzing:
A. Archeological Evidence.
- seeds, pollen grains, and fragments of plants – these tell us what types of plants were associated with the culture and perhaps being eaten and cultivated. Pollen grains are especially good tools because they are resistant to decay (last a long time) and can be readily identified;
- tools of cultivation, grinding or threshing;
- charred seeds – what kinds of plants were being cooked/eaten;
- phytoliths - silica particles; resist decay; can be identified to species
- coprolites – fossilized feces. These can be analyzed to see what types of foods were in the diet (i.e., look for seeds, plant fragments) and how they were eaten (i.e., cooked vs. raw);
- drawings (art) – to show plants and animals important in culture;
- animal bones, feathers, shells or other remnants
B. Radiocarbon Dating.
This provides a "clock" to determine dates/ages of archaeological materials. Carbon-14 and carbon-12 are naturally occurring isotopes (forms) of the carbon atom, which is the basic building block for virtually all molecules in living organisms. There is a stable ratio of carbon-14 to carbon-12 in nature. Both isotopes are incorporated into plants (and other living organisms) in the proportion in which they occur. Hence the amount of each in a living organism reflects the natural abundance of the two isotopes.
However, carbon-14 is radioactive and it decays to nitrogen-14 and a beta minus particle (energy). This process has a half life of 5700 years, which means that if you start with 1.0 pound of carbon-14, 5700 years later you will have 0.5 pounds of carbon-14 (and lots of nitrogen-14). In 11,400 years there will be 0.25 pounds of carbon-14 and so on. Thus, we can measure the ratio of carbon-14 to carbon-12 ratio to give an idea of age since we know the decay rate. The older the sample, the lower the amount of carbon-14.
VII. WHEN did agriculture originate?
All evidence points to somewhere between 10,000 and 15,00 ybp.
VIII. WHERE did agriculture originate?
A. Varied Landscape - hilly/mountain regions.
These hilly areas would have many micro-environments, which means there would be a great diversity of plants for potential domestication. Further, there would less migration of people, less plant cover to remove for cultivation, lower rain fall, fewer weeds and pests.
B. Mediterranean Climate
Mild, wet winters and hot, dry summers such as those that occur in coastal California, Chile, South Africa, parts of s. Australia, and obviously, the Mediterranean. This climate would favor plants that died back during the long dry summer and put energy into big, edible seeds. This area has a high percentage of annual plants (like most of our crops) and self-compatible plants (don't require cross-pollinating which would insure a more successful crop and that plants with desirable traits would be self-propagating.
C. Major Centers of Crop Domestication (two in the Old World and one in the New World)
- Near East (9 - 14,000 ybp) This region is also called the "Fertile Crescent" which now comprises regions of Syria, Jordan, Iraq. Jarmo is a cave system in Iraq that has been particularly well studied. Wheat, barley, lentils, and peas were among the earliest crops domesticated here.
- SE Asia (11,500 ybp). Hard to pinpoint precisely, because conditions not as favorable for preservation of archaeological materials. Rice, hemp, and soybeans
- Americas. Peru (6000 BC - evidence for cultivation of 2 species of beans & a pepper). Mexico (5000-7500 BC - gourd, beans, pepper, squash, chili) Caves in Tehuacan. Tamaulipas evidence for maize (5000 BC).
- Although these are the three major center, note that crops were also domesticated in many other areas of the world (i.e, US – sunflowers; African – yams, sorghum)
D. Independent vs Diffusionist Origin.
There has been an argument about whether agriculture originated once (diffusionist origin) and then spread around the globe; or whether it originated independently around the globe (independent origin). Most currently believe that it happened independently because (a) its not too difficult to imagine it occurring; and (b) it happened fast.
E. The Impact of Geography.
Jared Diamond suggests that the rapid spread of agriculture in the Old World was largely a function of geography and the horizontal axis of the continent. Once agriculture originated in the Fertile Crescent, it probably spread quickly to Europe because the climate was very similar. In contrast, in the New World, the axis is primarily vertical meaning that it was more difficult for crops to spread north or south from a single region of domestication.
IX. Nickolai Ivanovich Vavilov (1940's).
Looked for "centers of agriculture." Assumed that (1) the centers would be located where wild relatives occur; and (2) where there is lots of natural diversity in crops. Vavilov recognized 8 major centers of crop domestication:
- Chinese (hemp, mulberry, tea, soybean)
- Indian (sugar, banana, breadfruit, coconut)
- Asian (apple, carrot, grape, pear)
- Near East (wheat, lentil, flax, fig)
- Mediterranean (beet, cabbage, olive)
- Abyssinian (coffee, castor bean)
- Mexico/Central America - avocado, bean, cocoa, maize, cotton, pepper)
- Andean - (manioc, peanut, tobacco, potato, tomato)
Note - (1) Vavilov's centers are less defined than once believed; (2) some "characteristic" foods are not native (i.e., tomato & peppers are not native to Italy; apple pie and peas not native to North America)
Vavilov was a neat guy. He was born 26 November 1887 (or 13 Nov, using the old style calendar). His father was a cloth merchant. He had 2 sister2, 1 brother (Serge who became president of the Academy of Science of the USSR, physicist). Vavilov married Elena Ivanovna Barulina and they had two sons, Oleg & Yuri, both physicists.
Vavilov studied at the Petrovsky (later Timiryazev) Academy of Agriculture Science from 1906 to 1910. His graduate thesis was on the immunity of cereals to disease. In 1911 he served in Petersburg as an assistant economic botanist. 1913 - studied abroad in Britain where he worked with Bateson, Punnett, Haeckel on genetics and plant breeding. 1917 - became a professor of plant breeding at Univ of Saratov. 1920 - returned to Leningrad which was under Lenin's direction at the institute of plant industry. Vavilov revolutionized plant breeding. Studied crop evolution, practical breeder. To breed more resistant and better crops he advocated using the total genetic diversity of crops themselves and wild species. This is obvious now, but it was new at the time. Vavilov laid the foundation for the conservation of genetic resources. he was supportive of traditional farming systems and the need to questions farmers to collect data before valuable information was lost.
He identified regions of high diversity, usually in the mountains, that we inhabited by ancient human cultures. He termed these centers of diversity and suggested that this is where crops originated. Not true today, relies more on living prototypes and archaeological remains. Vavilov also distinguished primary from secondary crops.
Man of energy, charisma, enthusiasm, scientific integrity. One of my favorite quotes attributed to him: "Life is short - one must hurry".
In 1940 he was arrested on collecting trip to Ukraine - imprisoned in Leningrad. In July 1941 he was sentenced to death for agricultural sabotage, spying for England. The sentence was commuted to l0 years. Stalin controlled everything, including science. Said genetics was counter to Marxist theories and passed law against. Here is another example of why it is bad to try to legislate science. They believed that the group/workers could collectively do anything to modify environment. Lysenko - appointed science dictator. He put the kabosh on Vavilov and associates. Lysenko was finally removed in mid 60's, when Kruschev fell. Sadly, this put Soviet genetics back several decades and they are only now "catching up".
Vavilov was incarcerated in Soratov prison, Moscow - essentially an underground death cell. Died Jan 26, 1943.
X. HOW did our ancestors learn about cultivating crops?
A. Dump Heap hypothesis (Edgar Anderson, 1952).
Garbage sites may have been the breeding grounds for various species. They would have been open sites, rich in nutrients. Therefore, agriculture may have started accidentally.
B. Convenience Hypothesis (Michener in The Source).
Wife of Ur planted near here dwelling so she wouldn't have to search. Also, note in this idea the notion of the "genius" or "brilliant sage" idea - that agriculture arose as a result of a flash of brilliant insight ("Eureka"). Further, it highlights the importance of women in the process, which was almost surely the case.
C. Increased Familiarity Hypothesis (Braidwood).
Suggests that agriculture slowly as more people become more familiar with plants and animals. A related idea suggests that ancestors knew about growing plants, that there was nothing special or overly complex about it (related to the previous hypothesis). However, the main difference was in the degree of attention given to the process resulting in the domestication of species.
D. Religion (C.B. Heiser, Jr).
Suggests that religions were very important in the origin of agriculture. Most cultures have some type of myths/stories about the origins. For example, the myth of Persephone and Judeo-Christian ideas in the Old Testament.
The rites of first fruits were widespread. Gatherers return some of the first collection back to sacred sites as offerings to the gods. May have been scattered or buried and came up the next year. This idea also would explain artificial selection (domestication) - the best seeds would have been returned to the gods. Some evidence: (1) sacrifices associated with crops were common; (2) Venus figurines representing Earth Mother and female fertility common. The phallus didn't become important until late, perhaps when the male role was fully understood. Perhaps as some speculate, females become subjugated at this point; and (3) sex was often associated with sowing seeds. Lots of symbolism in plowing the earth, rain to fertilize, female womb, etc.
E. Storage Hypothesis
Like a squirrel forgetting a buried seeds, plants developed from underground storage caches or burial sites in which plants were ritually interred with the bodies.
XI. WHY did agriculture originate?
Especially considering that hunter/gatherers like the !Kung: (1) are not nutritionally deprived (studies have shown there diet is more than adequate); (2) do not spend any more time procuring food than farmers; and (3) know about plants/growth and consciously choose to not grow plants. This suggests that agriculture originated because it was necessary to do so. Why?
A. Changing Climate Hypothesis (V.G. Childe, 1936).
Suggested that a change in the climate in the Near East, lead to desiccation, brought people together in oases, leading to the need for increased food production, less mobile lifestyle.
B. Population Pressure Hypothesis (Mark Cohen, 1973).
Increasing mouths to feed forced a more reliable and productive means to obtain food. Suggested that planting was known but not necessary until population pressure forced the need.
C. Food Abundance Hypothesis (Carl O. Sauer, 1952).
In SE Asia, the fishing villages would have had an abundance of food, leading to a more sedentary lifestyle, leading to experimentation with agriculture. Another possibility related to this idea is that the overabundance of food lead to stockpiling with in turn, would have lead to sedentary lifestyle to store and protect.
D. People and plants became dependent on one another (coevolution between people and plants – David Rindos)
Rindos suggests that people became dependent on artificially selected plants and the plants became dependent on people for propagation.
E. Summary – probably no one "correct" method – different routes to agriculture in different regions as long as: (1) plants available for domestication; (2) knowledge available by people to grow plants; and (3) decrease ability in landscape to support hunting/gathering lifestyle.
XII. WHAT was cultivated?
A. Multipurpose crops.
Crops that provide more than a single product, may have been first. These include coconut (food, fiber, building material, etc.) and hemp (food, fiber, drug).
B. Root crops.
They are rich in carbohydrate, some are always left in the field, vegetatively propagated, simpler and easier than seeds. This idea is from Carl Sauer. There is no good supportive evidence, but it is unlikely these materials would have preserved well.
They are a good carbohydrate source; dry and preserve easily; all cultures (with the exception of the high Andes that used a root crop and drying method) developed relied on a domesticated cereal.
D. Why have there been so few new crops domesticated since the work of our ancient ancestors?
E. Accidental Byproducts.
Many crops may have been domesticated as an accidental byproduct of domesticating another crop. For example, oats and rye are considered secondary crops since they developed from weeds in wheat fields (primary crop).
F. Trends in domestication.
During the domestication process, which occurred either intentionally or perhaps unintentionally, those plants that showed features most suitable to human use were propagated, result in a change of characters from wild ancestors. We can graphically represent this process by plotting on the Y axis the number of individuals with a specific variation and on the X axis a measurement of some variation in the plant such as crop yield. The general pattern is a bell-shaped curve, some individuals have very high yields, some low, but most are average. If the high-yielding individuals are selected, over time, the population will consist almost entirely of high-yielding ones. This is artificial selection.
The following lists some of the traits and trends that were selected from the wild ancestors. Note that these were required to improve the nutritional quality, yield, make the plant palatable, easier to harvest, adaptable to competition with other plants, able to survive in cultivation.
|Table 1. General trends in crop domestication|
|branching pattern (branched vs. not)||branched||unbranched|
|ripening (synchronous vs. not)||asynchronous||synchronous|
|seed dormancy (+/-)||present||absent|
|shattering (seeds shed from parent plant vs. not) and dispersal (yes vs. no)||shattering heads, high dispersal ability||non-shattering heads, loss of dispersal|
|threshing (hard vs. easy)||hard||easy|
|germination (synchronous vs. not)||asynchronous||synchronous|
G. New World vs. Old World Agriculture.
There were some differences in the agriculture practices. These are summarized below in Table 2.
|Table 2. Comparison of New and Old World Agriculture|
|Feature||New World||Old World|
|planting technique (individual seeds vs. broadcast)||plant individual seeds (maize)||broadcast seed (wheat)|
|animals (few vs. many)||few animals (dog)||many animals|
|irrigation (early vs. late)||irrigation late||irrigation early (5000 BC; which has led to a variety of problems such as salinization and desertification. Saw a change to shift to more salt tolerant crops like barley).|
H. Temperate vs. Tropical Agriculture
|Table 3. Comparison of temperature vs. tropical agriculture|
|Cropping system (monoculture vs. multi-crop)||monoculture||multi-cropping|
|stability (fixed plots vs. shifting cultivation)||fixed plots with delineated fields||shifting cultivation (slash and burn)|
|crop storage (storable vs. not)||storable crops (i.e., maize)||limited storage (development of alternatives such as fermented products, i.e., breadfruit)|
|soil fertility (fertile vs not)||fertile||infertile|
I. Crop storability – breadfruit pudding. Mutiny on the Bounty. survive periods of famine, withstand sieges