Part 1. The Origins of Agriculture
A. For most of their early history, humans survived as
foragers or hunter-gatherers, gathering
wild plants and hunting animals in their natural environment.
B. Around 10,000 years ago in many areas of the world,
there was a shift in human endeavor
from foraging to farming. Why this happened is not known, but it appears to have formed the
basis of advanced civilization in both the old and new worlds.
II. Early foragers
A. These early
knew which plants were edible, which were poisonous, and which had
medicinal properties. They knew which plants could be used as dyes, which could be used for
weaving or building materials.
B. One group, the !Kung have foraged Africa for at least
10,000 years. Their diet consisted of
2300 calories per day, and two thirds of it was plant based, particularly, fruits, nuts, melons,
berries, roots, and greenery.
III. Agriculture: revolution or evolution
A. About 10,000 years ago, human cultures began the practice
different areas of the world; the near East, the far East, and in Mesoamerica.
2. Eventually, there was a transition between simple foraging where nomadic bands followed the plants around, to sedentary agricultural societies, where the people stayed in one place, and grew crops. The foragers changed from collecting wild cereals to actually cultivating them.
3. See this exhibit about stone age hunter-gathers in Great Britain; be sure to follow the several links.
IV. Early sites of agriculture
A. The Near East: an area known as the "fertile
parts of Iran, Iraq, Turkey, Syria, Lebanon, and Israel.
2. Early plants domesticated were wheat, barley, pea, lentil, and vetch. The domesticated animals were dogs, goats, and sheep.
3. Similar developments occurred in Egypt where the first ornamental gardens were developed.
B. The Far East: Southeast Asia in Thailand, and the Yellow
and Yangtze river valleys in
2. Found rice, millet, broomcorn millet, rape, and hemp. There was also evidence of domesticated cattle, pigs, dogs, and poultry.
C. The New World:
a. Eastern North America: Localized plants few of any importance except sunflower
(west) and cranberries (east); some hunting of deer, turkey and fishing (both fresh and
brackish water), e.g.: Cherokee
b. Western North America: Trees and shrubs with some herbs: pine nuts, amaranth;
considerable hunting and fishing; e.g. pueblo dwellers
c. Mexico: Principle crops were corn and beans; some hunting, limited fishing. Two
major civilizations established: Aztec and Mayan where corn (or maize) was considered
d. South American: Principle crop was potato; some hunting; limited fishing. One major
civilization: Inca mainly of Peru. Domesticated llamas. Cacao or chocolate also was
2. Emphasis was clearly on plants with comparatively few animals.
a. Crops like corn, squash, beans, amaranth, and to less extent squash, avocado and
potatoes were adopted and cultivated in all areas.
b. The dogs was widely domesticated but likely arrived with early human from Asia as
c. Tobacco was widely cultivated as a mild narcotic.
3. History of American agriculture
a. an outline of American history
b. history of North Carolina agriculture
c. history of Knox County, Ohio agriculture
D. World recipes reflect origins of agriculture
V. Characteristics of domesticated plants
A. Plants that have been domesticated are genetically distinct from their wild progenitors.
2. Once a plant is domesticated, it is artificially selected to suit human needs and not necessarily for survival value. In fact, some modern cultivated plants could not even survive in the wild. For example, seeds dispersal of corn does not happen because of the way modern husked ears have been selected.
3. Many cultivated plants and domesticated animals came from the same regions of the world, called centers of origin. From these centers, cultivated plants were dispersed and spread to other areas of the world
B. The wild ancestors of several cultivated crops still
exist. As these are often the only sources
of germ plasm for the continued development of new cultivars, or human-selected kinds of
domesticated crops, collection of seed and protection of wild populations is now an
international goal in maintaining genetic diversity of crop plants.
C. Many of the early explorers were responsible for
introducing plants from around the world
into western European culture
VI. Agriculture today
A. Now that we have seen how agriculture began, now lets
compare some statistics about
present day agriculture
a. This 3% is about all that is suitable for cropland and grazing, the rest is Tundra,
boreal forest, tropical rain forest.
b. The best land is already in production. Any new lands would be marginal.
2. The United States
a. The land area of the continental US is about 1.9 billion acres.
i. 310 million acres is cropland (16%)
ii. 650 million is grassland pasture and range for grazing animals (34%).
b. Four major crop plants- corn, wheat, soybeans, and hay are planted on 80% of the
cropland- (240 million acres)
c. All vegetables, fruit and nuts, (including potatoes, rice apples, tomatoes, peanuts,
beans, sugarcane, and sugar beets that we consume and export are produced on 7% of
the crop land.
d. Cotton is planted on 12 million acres (4%).
B. Since 1950 (45 years) agriculture related research
in the US has provided some
dramatic increases in the yield per acre of many important crops.
a. soybeans 100-150% 2-2.5 fold increase; 1987-1996 figures
b. wheat- 100-150% increase 2-2.5 fold increase; 1987-1996 figures
c. corn- 270% or 3.7 fold increase; 1987-1996 figures
And all with no new land being used.
2. The US has 22% of the world land area planted in corn it produces 47% of the world crop.
3. These increments in yield are the result of many kinds of improvements:
a. improved crop varieties
b. improved cultural practices such as plant and row spacing, crop timing, tillage, and
c. improved pest control- pest resistant cultivars, better weed, insect and disease
d. tailored fertilization
4. As a result, there has been this tremendous increases in crop yields and efficiency of crop production.
a. In the U.S., the percentage of disposable family income spend for food today is the
same as it was 40 years ago in 1955.
b. In 1994:
i. percentage of population engaged in farming: US - 2% China - 80%
ii. percentage of disposable income spent on food: US - 16% China - 65%
c. In the US, an additional 20 million people are engaged in the spin-off from crop
production, transportation, wholesaling, and retailing.
d. In the United States we pay three times more for taxes as for food.
C. Summary of agriculture in the United States for 1992
|Lands in farms (acres)||943,321,506|
|Total cropland (acres)||434,365,878|
|Harvested cropland (acres)||295,936,976|
|Irrigated land (acres)||49,404,030|
|Market value of products||$162,608,334,000|
|Crops including nurseries||$75,228,256,000|
|Cost of production||$130,779,261,000|
|Net average profit per farms||$15,801|
|Principal occupation is farming||1,053,150|
|Principal occupation is not farming||872,150|
Part 2. Human Nutrition - Why people need to develop agriculture
I. Examination of a typical nutrition label from a box of breakfast cereal shows the nutrients broken up into several classes, after the general information on servings.
Serving Size 1/2 cup (114 g)
Servings Per Container 4
|Amount Per Serving|
|Calories 90||Calories From Fat 30|
|% Daily Value*|
|Total Fat 3g||5%|
|Saturated Fat 0g||0%|
|Cholesterol 0 mg||0%|
|Sodium 300 mg||13%|
|Total Carbohydrate 13g||4%|
|Dietary Fiber 3g||12%|
|Vitamin A||80%||Vitamin C||60%|
|* Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs:|
|Total Fat||Less than||65g||80g|
|Sat Fat||Less than||20g||25g|
|Calories per gram:|
|Fat 9||Carbohydrate 4||Protein 4|
II. What does this all mean? These are important nutritional categories for humans:
B. Macronutrients - required in sufficient amounts
1. Calories: lipids, carbohydrates
C. Micronutrients - these are essential for proper nutrition, but required in smaller amounts
A. Food nutritional value is measured in the amount of energy supplied from the food source.
1. The unit of measurement is
Technically, this is the amount of energy required
to raise the temperature of one gram of water one degree C.
2. In humans, two thirds of all calories taken in are used to maintain the body temperature.
B. Food energy is normally measured in thousands of calories
or Kilocalories of kcal. So 1000
calories = one kilocalorie.
C. We get calories from four food groups: fat (9 calories
per gram), alcohol (7 calories per
gram), carbohydrate (4 calories per gram), and protein (4 calories per gram).
1. Typically, humans require between
1200 and 3200 Calories per day to maintain
themselves. The Percent Daily Values listed in food labels are usually based on a 2,000
a. How many calories do you need?
b. Facts about calories.
c. Calories that don't count.
IV. Macronutrients: Lipids - Fat and Cholesterol
A. These compounds belong to a general class of organic
molecule called lipids
(refer to Lecture 4). Their main chemical feature is that they are insoluble in water. Ninety five
percent of all lipids in the body are in the form of fats and oils called triglycerides.
compounds formed from glycerol and fatty acids. Fatty Acids are the
simplest type of lipid, and are used to also make up phospholipids.
a. Fatty acids: Each fatty acid has a carbon chain with hydrogen atoms attached. The
different fatty acids differ in number of carbon and hydrogen atoms.
b. Essential fatty acids:
i. the body can make most fatty acids
ii. however three must be supplied in the diet: linoleic, linolenic, and arachidonic acids,
designated as the essential fatty acids
iii. the main source of these is from vegetable oils.
c. Saturated and unsaturated fatty acids
i. Fatty acids are separated by whether they are saturated or unsaturated; this refers to
the amount of single bonds between the carbon atoms, which in turn determines the
number of hydrogen atoms that can be bound to the carbons
ii. If all the carbon atoms are joined together by single bonds, and all possible
hydrogens are attached, the fatty acid is saturated.
iii. If some double bonds occur between the carbons, then the number of hydrogen
atoms that can be bound is reduced, and the fatty acid is unsaturated.
iv. All food fats contain a mixture of saturated and unsaturated fatty acids. Saturated
fatty acids are solid at room temperature for example butter and beef fat, and
unsaturated fatty acids are liquid at room temperature, for example corn oil and
d. Fatty acids are long chains of carbon and hydrogen atoms that are a
major source of body energy.
1. This is a sub category of lipids
known as steroids.
is a vital component of
cells as a part of cell membranes, as well as being used to synthesized several of the human
sex and other hormones.
a. It is synthesized in the liver from saturated fatty acids, or absorbed in the intestine from
eggs, butter, cheese and meat.
b. Plant sources do not contribute dietary cholesterol directly, and in fact contain
unsaturated fats, which are known to lower blood cholesterol levels.
2. Because cholesterol is insoluble in the blood, it is transported by molecules called
lipoproteins. These lipoproteins exist in two forms, high density HDL and low density
a. LDL forms of cholesterol can be taken up by cells lining the arteries resulting in excess
cholesterol blockages of the arteries, and a restriction of blood flow. This can lead to a
heart attack if the coronary arteries are involved.
b. HDL forms of cholesterol help to reduce the levels of LDL cholesterol.
c. What levels of cholesterol should you maintain? (from Pacific Health, L.L.C.)
i. Indications of low risk: These are the most commonly agreed upon observation for
cholesterol levels that best accommodate the maintenance of a healthy heart.
Total cholesterol count below 200 mg/dl
LDL cholesterol level 130mg/dl or lower
HDL cholesterol levels 35mg/dl or greater
LDL to HDL ratio less than 3
Total cholesterol to HDL cholesterol ratio 3.5 or lower
ii. Indications of medium-high risk: Any of these traits indicates medium risk of heart
Total cholesterol level from 200mg/dl to 239mg/dl
LDL cholesterol level from 130 to 159
Total cholesterol to HDL ratio from 3.5 to 4.5
iii. Indications of high risk: Any of these traits indicates high risk of heart disease.
Total cholesterol count 240mg/dl or greater
HDL cholesterol level less than 35mg/dl
LDL cholesterol to HDL cholesterol ratio of 3 or greater
Total cholesterol to HDL cholesterol ratio of 4.5 or greater
iv. If your cholesterol levels indicate medium or high risk, you should consult your
physician. Most people can control their cholesterol levels through a healthy low-fat diet
and regular exercise. Some people will require medicines to control their cholesterol
V. Macronutrients: Carbohydrates
A. Carbohydrates are grouped together as sugars and starches,
but also are classified as to
how many sugar units are present in the molecule (see Lecture 4).
1. Glucose- The basic building
block of all carbohydrates, and the most abundant of all the
sugars. A single glucose molecule is called a monosaccharide. It is the form of sugar that is
transported in the blood to all the cells in the body. Cellular respiration converts glucose into
energy necessary for life.
2. Fructose and galactose are also common monosaccharides with basically the same
3. Disaccharides- when two monosaccharides are joined together, they make up a
disaccharide. For example: One glucose unit and one fructose unit together make up the
disaccharide called sucrose. This is the form of sugar found on the dinner table. Another
example of a disaccharide is lactose, the sugar found in cow's milk. These disaccharides are
broken down into monosaccharides in order to be used by the body.
4. Polysaccharides- These are also known as complex sugars, contain hundreds or
thousands of individual sugar units, usually glucose. There are three forms of
polysaccharides important for human nutrition. The arrangement, number and way the
glucose units are joined together is what distinguishes one from the other.
a. Starch- This is the storage form of glucose found in plants. It is found in the seeds,
fruits, tubers (potato) and roots. The majority of starch in the human diet comes from
wheat, rice and corn as grain crops, potato, sweet potato, and cassava the underground
crops, and beans and peas, the legumes. Our body breaks down starch to glucose by
enzymes in the saliva, and small intestine.
b. Glycogen- This is the storage form of glucose in the human body found mainly in the
liver and skeletal muscles. Excess glucose in the blood from food is converted into
glycogen and stored. Unfortunately, we can only store a day's supply of glycogen in the
liver, the rest being converted into fat. During exercise this glycogen is converted back
into glucose to be used for energy. This is why athletes practice "Carbo loading" before
an athletic event. They eat excess amounts of starch foods to build up muscle glycogen.
c. Fiber- This is derived from plant sources and is mainly comprised of cellulose,
lignin, hemicellulose and pectin. It is not digestible, but provides bulk. Cellulose is again
formed from glucose, but humans do not have the proper enzymes to digest it. Foods
with fiber include grains, legumes, fruits, and vegetables. Dietary fiber comes in two
i. soluble fiber - found in psyllium husks and is the type that makes wet oatmeal sticky,
shown to reduce levels of cholesterol and appears to be associated with lowered heart
ii. insoluble fiber - the sponge-like version in bran and in fruit and vegetable skins
which absorb water, prevent constipation, and may lower colorectal cancer risk
VI. Macronutrients: Proteins
This is a group of large molecules that perform many functions in the body. One type of protein is insulin, a hormone produced by the pancreas to regulate the metabolism of glucose and other carbohydrates. They are constructed from smaller building blocks called amino acids (see Lecture 4). Usually there are 20 naturally occurring amino acids that are used in protein synthesis.
A. Essential amino acids: In order to successfully synthesize
proteins the human body requires
the presence of all 20 of the amino acids. However, the human body can only synthesize 11 of
the 20. Nine others absolutely must be obtained from the diet. These are called the essential
amino acids. These amino acids cannot be stored by the body, so must be continually
taken in via the diet. Lack of any of these can result in serious protein deficiency diseases.
B. Complete Proteins- These proteins contain all the essential
amino acids. Proteins obtained
in the diet from animal sources are complete. Those obtained from plant sources are
incomplete, deficient in one or more essential amino acids. In order to get all the essential
amino acids from plant sources it is necessary to combine different plant sources. For example,
beans and corn, the traditional diet of the Mexican indians provides all the essential amino
digestion requires the use of proteins in the form of digestive
there is a constant turnover in the body's supply of proteins. For proteins in your diet, see
proteins for athletes.
VII. Micronutrients: Vitamins
Vitamins: Molecules that are essential for the normal functioning of certain enzymes in many metabolic pathways of the body. These are called coenzymes. Others are directly involved the synthesis of essential compounds in the body. They are classified into two groups; fat soluble (A, D, E, K) and water soluble (C and B-complex). For a food guide to vitamins and minerals, see this nutritional science course at Cornell.
A. Vitamin A
1. This vitamin is very important
in the formation of visual pigments in the retina of the eye.
Each pigment is made up of a protein molecule, and a form of vitamin A called retinal.
These pigments are present in the photoreceptor cells of the eye. Night blindness is one of
the earliest signs of Vitamin A deficiency.
2. Vitamin A is necessary for the maintenance of epithelial tissues that line both internal and
external body surfaces, an area equal to one fourth of a football field.
3. It also helps the body fight infections and helps sustain the immune system.
4. Food sources of vitamin A is animal liver and is in the form of retinol. Plant sources
provide beta-carotene found abundantly in many yellow, orange and dark green fruits and
vegetables. Beta-carotine, when split into two molecules, forms retinol in the body. Unsplit,
beta-carotine is an antioxidant. Vitamin A deficiency can reduce the health of the skin and
epithelial tissues, affect digestion and absorption of nutrients, cause infections, and stop
B. Vitamin B complex This is a complex of eight
vitamins, which serve as coenzymes in
literally thousands of chemical reactions in the body. They are water soluble and can be
leached out of food during preparation if food is prepared in water.
B1) is part of the coenzyme thymine pyrophosphate, which
is involved in the breakdown of carbohydrates by the body. Since its role is metabolic, the
main signs of deficiency are fatigue, depression, mental confusion etc. Good dietary sources
of thiamine include meat, especially pork and liver, whole grains, seeds, nuts and legumes.
2. Niacin (Vitamin B3) collectively this includes two compounds, nicotinic acid and
nicotinamide. Either are used in the coenzymes NAD+ and NADP+ which are important in
oxidation-reduction reactions of the body. Without these reactions in the body, release of
energy from food breakdown cannot occur and cellular death results. The most common
ailment due to niacin deficiency is called pellagra, the symptoms are referred to as the 4 Ds:
dermatitis, dementia, diarrhea, and death. In the early years of this century, death was
surprisingly common in the southern states. Its cause was discovered by Dr. Joseph
Goldberger in 1914, one of the first efforts of what would eventually become The National
Institutes of Health. Food sources rich in niacin include meat, poultry, fish, eggs, nuts, seeds
3. Vitamin B12 (Cobalamin) - This vitamin does not occur naturally in any food of plant
origin, but only occurs in animal sources, where it is widely available. It is made from
bacteria and is only present in foods that contain the bacteria or from animals that have
ingested the bacteria. Vitamin B12 is involved in energy release from food, and nucleic acid
synthesis. The most common cause of deficiency is pernicious anemia characterized by the
production of improperly formed red blood cells. Symptoms include fatigue and weakness.
C. Vitamin C
C or ascorbic acid is obtained from fresh fruits and vegetables. Since
water soluable, they can be leached out of food during preparation.
2. The most important role of vitamin C is in the synthesis of collagen, a connective tissue
that holds body cells and tissues together. Collagen is the most abundant protein in the
body, and is found in bones, teeth and cartilage.
3. For centuries, sailors on long ocean voyages contracted Scurvy, a disease that could
cause bleeding of the gums and under the skin, fatigue, brittle bones and even sudden death
due to internal bleeding. It is now known that scurvy is caused by vitamin C deficiency, and
is directly traced to the bodies inability to make collagen.
D. Vitamin D
1. The primary function of Vitamin
D is the regulation of calcium and phosphorous levels,
especially for normal bone development. The vitamin acts on the absorption, and removal of
calcium from bones, and retention of calcium by the kidneys.
2. The human body can synthesize Vitamin D on exposure to sunlight.
3. Deficiency symptoms are most evident in bone formation. The most striking is a
malformed skeleton in children, a disease called rickets.
VIII. Micronutrients: Minerals
A. Inorganic compounds that exist in the body as ions,
or are a part of complex molecules. At
least 17 minerals are required for normal metabolic activities. They can be major minerals,
required in amounts greater than 100 mg/day, or trace minerals of which only a few mg are
required per day.
Calcium: This is
the most abundant mineral in the body, with the average adult containing
800 to 1300 g of the element. 98% is found in the bones and teeth. Its concentration is
under control of several hormones and vitamin D.
a. Calcium deficiency leads to osteoporosis, a degenerative bone disease which can be
easily prevented with a proper level of calcium in the diet. This affects some 15-20 million
Americans. Bone density is greatly reduced and bones fracture easily.
b. Milk and milk products are the best sources of calcium, but it is also present in
dark green leafy vegetables and many seeds. The recommended daily allowance for
calcium is about 1200 milligrams. One cup of milk supplies about 300 milligrams of
2. Iron: Among the trace minerals, iron deficiency is common in women and children and
care must be taken to insure that the diet supplies sufficient quantities.
a. Meat, fish, shellfish and poultry are excellent iron sources.
b. The iron from animal sources is present as heme iron, or nonheme iron.
c. The most important role of iron is as a component of hemoglobin, the molecule that
carries oxygen in red blood cells. It is the iron that produces the red color in blood. Iron
is also found in myoglobin, the oxygen carrier in muscle.
d. Iron deficiency has its main effect on red blood cells, and leads to iron deficiency
anemia. This is the most common dietary deficiency disease in the world. Menstruating
women are often at risk as are those who are pregnant.
e. Too much iron may also cause health problems, possilby heart attacks.
-Other micronutrients necessary for health? Phytochemicals
-antioxidants such as carotenoids (e.g. lycopene) and flavonoids
IX. Dietary guidelines
A. Research has shown that beneficial changes in diet
can reduce the risk of developing many
of these nutritional diseases.
B. Balancing Nutritional Requirements
1. Don't become
maintain correct levels
of calories consumed.
2. Reduce overall fat consumption.
3. Reduce saturated fat consumption.
4. Reduce cholesterol consumption.
5. Increase consumption of grains, vegetables, and fruits; high fiber.
6. Reduce the consumption of refined sugars (sweetners).
7. Limit intake of sodium (hypernatremia, sodium in foods).
8. Limit alcoholic consumption.
CyberDiet (Commercial site)- shows the nutritional content of specific foods
Increased life span through nutrition-reduced calorie diet and plant antioxidants
Dietary guidelines for Americans
Enjoy a variety of foods
10 tips to healthy eating
Importance of a balanced diet
Benefits of Vitamin E
Vitamin K: blood clotting
A major review
History of food development
Brief history of agriculture
Evolution of crop plants
What is crop evolution: A useful summary and preview
American Indian History
Brief history of American Indians in New Mexico
Anasazi: A Southwestern People
Indian stories about corn: Sioux, Cherokee, Chippewa, Abnaki
Central American history
A brief history of Mexico
A brief history of Central America
European agriculture history
How agriculture came to central Europe by Peter Bogucki
Neolithic landscapes in Poland: Technical but informative.
Recently discovered Paleolithic cave paintings in France
A summary of fossil hominids
Brief history of the U.S. Department of Agriculture
United States Agricultural Statistics, 1982-1992
Maryland agriculture census
Back to BSCI 124 main page
Last revised: March 17, 1999 - Browning