Part 1. The Origins of Agriculture
I. Introduction
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
foragers
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
of
agriculture
in several
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
crescent" of
Mesopotamia
which includes
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
China.
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
a
god.
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
important.
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
well.
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
2. Far East: rice
(Japanese,
Chinese,
Vietnamese)
3. Mexican: corn, beans
(menu,
traditional
dishes)
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
others
c. improved pest control- pest resistant cultivars, better
weed, insect and disease
control
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
| Farms | 1,925,300 |
| 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.
| Nutrition Facts 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% | ||
| Sugars 3g | |||
| Protein 3g | |||
| Vitamin A | 80% | Vitamin C | 60% |
| Calcium | 4% | Iron | 4% |
| * Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs: | |||
| Calories | 2,000 | 2,500 | |
| Total Fat | Less than | 65g | 80g |
| Sat Fat | Less than | 20g | 25g |
| Cholesterol | Less than | 300mg | 300mg |
| Sodium | Less than | 2,400mg | 2,400mg |
| Total Carbohydrate | 300g | 375g | |
| Fiber | 25g | 30g | |
| Calories per gram: | |||
| Fat 9 | Carbohydrate 4 | Protein 4 | |
II. What does this all mean? These are important nutritional categories for humans:
A. Calories
B. Macronutrients - required
in sufficient amounts
1. Calories: lipids, carbohydrates
2. Proteins
C. Micronutrients - these are essential for proper nutrition,
but required in smaller amounts
1. Vitamins
2. Minerals
III. Calories
A. Food nutritional value is measured in the amount of energy supplied from the food source.
1. The unit of measurement is
the
calorie.
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
calorie diet.
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.
1.
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
safflower oil.
d. Fatty
acids are long chains of carbon and hydrogen atoms that are a
major source
of body energy.
B. Cholesterol
1. This is a sub category of lipids
known as steroids.
Cholesterol
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
LDL.
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
disease.
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
levels.
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
composition.
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
types:
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
disease risk
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
acids.
C.
Protein
digestion requires the use of proteins in the form of digestive
enzymes. Therefore,
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
bone growth.
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.
1.
Thiamine (Vitamin
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
and legumes.
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
1.
Vitamin
C or ascorbic acid is obtained from fresh fruits and vegetables. Since
they are
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.
1.
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
calcium.
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
overweight,
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.
HUMAN NUTRITION
Diet
CyberDiet (Commercial
site)- shows the nutritional content of specific foods
Increased life
span through nutrition-reduced calorie diet and plant antioxidants
Nutrition
menu
Dietary guidelines
for Americans
Enjoy
a variety of foods
10
tips to healthy eating
Importance
of a balanced diet
Food labeling
Food
labeling
Vitamins
Vitamin
update
Vitamins
Benefits
of Vitamin E
Vitamin K:
blood clotting
AGRICULTURE
History
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.
Neolithic Northern
European Plains
Recently
discovered Paleolithic cave paintings in France
A summary
of fossil hominids
Agricultural statistics
Brief
history of the U.S. Department of Agriculture
United States Agricultural
Statistics, 1982-1992
Maryland
agriculture census
Last revised: March 17, 1999 - Browning
