Think of the earth as a living organism that is being attacked by billions of bacteria
whose numbers double every forty years. Either the …bacteria dies, or both die.
- Gore Vidal
 The evolution of Homo sapiens and a total population of about 2 billion took
about 200,000 years
 In 2015, the World population reached 7.3 billion people
 It’s estimated that there will be 2.5 billion more people by 2050
 Are there too many people already?
 Will technological advances overcome environmental resistance that
populations face?
 Should populations be controlled/limited?
 During the earliest parts of human history, our
population survived as hunter-gatherers.
 The population during this time was low;
estimated to be in the thousands.
 Like other species,
population size was
limited by
environmental
resistance factors, such
as competition for food
and water, predators,
and disease.
3
 At some point, estimated to be about 130,000 years
ago, Homo sapiens migrated out of Africa into
what would become the fertile crescent.
4
 The fertile crescent, as a “bridge” between Africa
and Eurasia, had an unusually high amount of
biodiversity.
 The eight “founder crops,”
including wild ancestors to
modern flax, wheat, barley,
and lentils, grew here.
 The ancestor species of
four out of the five modern
domesticated livestock animals were native to
here.
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 The presence of two major river systems also
stimulated the invention of irrigation.
 This period is known as
the Agricultural Revolution
and marked the first point
where humans moved from
a nomadic lifestyle to
settling in towns and
villages.
 Instead of hunting and gathering, humans began
growing and raising their own food supply.
6
 Agriculture gave humans a greater degree of
control over their food supply. As a result, the
population began to grow.
7
 The human population grew at a steady rate,
reaching about 800 million by 1800 A.D.
 Some density-dependent limiting factors were still
in place.
 Famines
 Western Europe, 400-800 A.D.
 Mayan Civilization, 800-1000 A.D.
 Little Ice Age, 17th century
 Great Potato Famine (Ireland), 1845-1847
 Disease
 Malaria (10,000 B.C.-present), cause of about half of all
human deaths
 Black Plague (14th century), Eliminated 1/3 of Europe’s
population.
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 The industrial revolution began a multitude of new
technologies and innovations.





Electricity
The steam engine
Water treatment
Antibiotics
Vaccines
 The overall impact was a massive drop in infant
mortality – the death rate in newborns.
 This led to an increase in overall average life
expectancy.
 Pre-industrial life expectancy in Britain was 25-40 years.
 Current life expectancy worldwide is 67 years.
9
World Population “Dots” Video. Population Connection, 2003.
 Industrialized farming, water treatment, and
modern medicine removed many densitydependent limiting factors.
 The human population began to grow
exponentially.
11
Planet Earth: Population 7.3 Billion
Billions of people
2011 (7 billion)
1999 (6 billion)
1987 (5 billion)
1974 (4 billion)
1960 (3 billion)
1930 (2 billion)
1800 (1 billion)
Time
Hunting and
gathering
Agricultural revolution
Industrial
revolution
Fig. 6-1, p. 122
 Exponential growth occurs when the population size
and its rate of growth both increase.
 It took over 70,000 years to reach 1 billion.
 150 years to reach 3 billion.
 25 years to reach 4 billion.
 20 years to reach 5 billion
 12 years to reach 6 billion.
 11 years to reach 7 billion.
13
 Another way of measuring growth is through
doubling time, an estimate of how long it will take
the population to double in size at its current rate
of growth.
 Doubling time is calculated with this equation:
70 / (Current % Growth Rate)
Year
1970
1980
1990
2000
2010
Growth Rate Doubling
Time
2.09
34 years
1.82
38 years
1.60
44 years
1.26
56 years
1.12
63 years
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 Demographics is the study of human populations.
 Includes comparing statistics such as births, deaths,
gender, race, and economic status.
 Developing countries have populations that tend
to be poorer, younger, and are growing much more
rapidly.
 Developed countries are wealthy, old, and tend to
have decreasing population sizes.
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 Population change =
(births + immigration) – (deaths + emigration)
 Crude birth rate
 The number of live births/1000/year
 Crude death rate
 The number of deaths/1000/year
NATURAL CAPITAL
DEGRADATION
Altering Nature to Meet Our Needs
Reduction of biodiversity
Increasing use of the earth's net primary
productivity
Increasing genetic resistance of pest species
and disease-causing bacteria
Elimination of many natural predators
Introduction of potentially harmful species
into communities
Using some renewable resources faster
than they can be replenished
Interfering with the earth's chemical cycling
and energy flow processes
Relying mostly on polluting and climatechanging fossil fuels
Fig. 6-A, p. 124
 Developing countries contain 80% of the world’s
population, and will account for 90% of its projected
growth.
19
12
11
High
10.8
10
Population (billions)
9
Medium
9.3
8
7
6
Low
7.8
5
4
3
2
1950 1960 1970 1980 1990
2000 2010 2020 2030
Year
2040 2050
Fig. 6-2, p. 125
 Comparing developed and developing countries
requires the use of these demographic variables:
 Life expectancy, or how long an average newborn
will live in a society.
 Most affected by infant mortality rate.
 The total fertility rate, the average number of
children a woman will have in her lifetime.
 A fertility rate above replacement level, 2.1, will generally
result in a growing population.
 Below replacement level results in a shrinking population.
 Gross domestic product per capita is a measurement
of standard of living.
 Total value of all goods and services produced in a country
per person.
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Country
GDP Per
Capita
Total Fertility
Rate
Life
Expectancy
United States
$49,965
1.89
78.6
Afghanistan
$620
6.16
48.7
Afghan market. Photo by Staff
Sgt. Russell Lee Klika
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 Life expectancy (and infant mortality) are highly
correlated with GDP, up to about $4000/year.
23
47 years
Life expectancy
77 years
Married women working
outside the home
8%
81%
15%
High school
graduates
83%
10%
Homes with flush
toilets
Homes with
electricity
Living in
suburbs
Hourly manufacturing job
wage (adjusted for inflation)
Homicides per
100,000 people
98%
2%
99%
10%
52%
$3
1900
2000
$15
1.2
5.8
Stepped Art
Fig. 6-7, p. 132
 The movement of individuals between areas can
have a major impact on population change.
 Emigration is when people move out of an area.
 More likely to occur in developing countries.
 Immigration is when
people move into an
area.
 More likely to occur
in developed countries.
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 In some developed countries, immigration offsets
or delays the normal population decline.
 The United States total fertility rate in 2011 was
1.89, below replacement level.
 The overall immigration was over 11 million.
 The population growth rate was 0.7%.
 Japan had a fertility rate of 1.39 in 2011.
 The overall immigration was just over 200,000.
 Their population growth rate is -0.2%.
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














Children as part of the labor force
Cost of raising and educating children
Availability of private and public pension
Urbanization
Educational and employment opportunities for women
Average age of a woman at marriage
Infant mortality rates
Availability of legal abortions
Availability of reliable birth control methods
Religious beliefs, traditions, and cultural norms
Children as part of the labor force
Cost of raising and educating children
Availability of private and public pension
Urbanization
Educational and employment opportunities for women
 Life expectancy - the average # of years an infant
can expect to live
 Infant mortality rate:
The infant mortality rate (IMR) is the number of
deaths of infants under one year old, per 1,000 live
births.
 High infant mortality rate indicates:
 Inadequate health care for poor women during pregnancy and their
infants (poverty)
 Drug addiction among pregnant women
 High birth rate among teenagers
Infant mortality rate
(deaths per 1,000 live births)
Less-developed
countries
World
More-developed
countries
Year
Fig. 6-10, p. 129
 Why are people living longer and fewer infants
dying?
 Increased food supply and distribution
 Better nutrition (less malnutrition and
undernutrition)
 Medical advances
 Improved sanitation
 When studying the demographics of a single
country, two of the most important factors to
examine are gender and age distribution.
 These variables are graphed as population
pyramids, and can provide valuable insight into a
country.
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 What is the overall shape of the graph?
 Is there a dominant age group or groups?
 What proportion of the 0-4 age group survives into the
elderly (60+) age groups?
 Are the male and female sides roughly equal?
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 The fertility rate and population growth patterns
in a given country will not remain constant. They
change based on a wide variety of factors.
United States Fertility Rates, 1911-2011
35
 Pronatalist pressures increase the likeliness of
individuals within a population to have more children.
 Source of pleasure, pride, comfort.
 Source of support for elderly parents.
 Aid in supporting family income.
 Counteracting high child mortality rates.
 Social status – importance of having a son.
 Most antinatalist pressures involve women.
 Higher education and personal freedom.
 More opportunities to earn a salary.
 Higher socioeconomic status.
36
 Countries will typically pass through a series of
stages as they industrialize and transition from
developing to developed countries.
 During the pre-industrial stage, food shortages,
malnutrition, poor sanitation, and lack of access to
modern medicine keep death rates high.
 All regions of the world were in this stage up until
the industrial revolution.
37
 During the early transition stage, access to food
and medicine improves, leading to a rapid drop in
death rates.
 Birth rates remain high, as family size is tied to
cultural norms and religious beliefs.
 Population size begins to increase exponentially.
38
 During the late transition stage, efforts are made to
reduce birth rate.
 Birth control and sex education gain greater acceptance.
 Women play a greater role in family planning.
 The population continues to increase, but more slowly.
39
 During the industrial stage, birth rates have fallen
back into balance with death rates.
 Total fertility rate is close to replacement level.
 The population stabilizes.
40
 During the post-industrial stage, birth rates
continue to fall due to antinatalist pressures
 Total fertility rate is below replacement level.
 The population size decreases.
41
42
Some Problems with Rapid
Population Decline
Can threaten economic growth
Labor shortages
Less government revenues with fewer
workers
Less entrepreneurship and new business
formation
Less likelihood for new technology
development
Increasing public deficits to fund higher
pension and health-care costs
Pensions may be cut and retirement age
increased
Fig. 6-11, p. 133
 Most demographers believe the world population
will stabilize sometime during the next century.
 Projections of
 Low
 Medium
 High
maximum population size:
8
9.3
13
billion
billion
billion
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