Human Populations

1
Human Populations

• Chapter 4

2
Outline

• Population Doubling Times
• Malthus vs. Marx
• Role of Technology
• Two Demographic Worlds
• Fertility and Birth Rates
• Mortality and Death Rates
• Population Growth Factors
• Demographic Transition
• Future of Population Growth

3
POPULATION GROWTH

• For most of human history, humans have not been
  very numerous compared to other species.
• It took all of human history to reach 1 billion.
• 150 years to reach 3 billion.
• 12 years to go from 5 to 6 billion.
• Human population tripled during the twentieth
  century.

4
Table 4.1
5
Human Population History
6
Population Doubling Times

• Rule of Thumb
• In exponentially growing populations
• 70 / annual growth Doubling Time
• 70 / 2.0 35 years

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LIMITS TO GROWTH

• Thomas Malthus (1798) argued human populations
  tend to increase exponentially while food
  production is plentiful.
• Humans inevitably outstrip food supply and
  eventually collapse.
• Human population only stabilized by positive
  checks.
• Humans are too lazy and immoral to voluntarily
  regulate birth rates.

8
Karl Marx

• Population growth is a symptom rather than a root
  cause of poverty and other social problems.
• Real causes of these problems are exploitation
  and oppression.
• The way to slow population growth and alleviate
  many social problems is through social justice.

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Malthus and Marx Today

• Neo-Malthusians - Believe we are approaching, or
  have already surpassed, the earths carrying
  capacity.
• We should make over-population issues our first
  priority.
• Neo-Marxists - Believe eliminating oppression and
  poverty through social justice is the only
  solution to the population problem.
• Wealth and resource distribution must be
  addressed.

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The Role of Technology

• Technological optimists argue that Malthus was
  wrong in his predictions because he failed to
  account for scientific progress.
• Current burst of growth was stimulated by the
  scientific and industrial revolutions.

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Can More People be Beneficial ?

• More people mean larger markets, more workers,
  and increased efficiency due to mass productions.
• Greater numbers also provide more intelligence
  and enterprise to overcome problems.
• Human ingenuity and intelligence.

12
HUMAN DEMOGRAPHY

• Demography - Encompasses vital statistics about
  people such as births, deaths, distribution, and
  population size.
• October 12, 1999, UN officially declared the
  human population reached 6 billion.
• Estimation at best.

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Two Demographic Worlds

• First is poor, young, and rapidly growing.
• Less-developed countries.
• Africa, Asia, Latin America
• Contain 80 of world population, and will account
  for 90 of projected growth.
• Second is wealthy, old, and mostly shrinking.
• North America, Western Europe, Japan
• Average age is about 40.
• Populations expected to decline.

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Estimated Human Population Growth
15
Table 4.2
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Fertility and Birth Rates

• Crude Birth Rate - Number of births in a year per
  thousand. (Not adjusted for population
  characteristics)
• Total Fertility Rate - Number of children born to
  an average woman in a population during her
  reproductive life.
• Zero Population Growth - Occurs when births plus
  immigration in a population just equal deaths
  plus emigration.

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Fig. 4.5
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Mortality and Death Rates

• Crude Death Rate - Number of deaths per thousand
  persons in a given year.
• Poor countries average about 20 while wealthier
  countries average about 10.
• Some rapidly growing countries have very low
  crude death rates compared to slower growing
  countries, due to a higher proportion of young
  people in the population.

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Life Span and Life Expectancy

• Life Expectancy - Average age a newborn can
  expect to attain in any given society.
• Worldwide, average has risen from 40 to 65.5 over
  the past century.
• Greatest progress has been in developing
  countries.
• Annual income and life expectancy are strongly
  correlated up to about 4,000.00 (U.S.).

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Table 4.2
21
Life Expectancy
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Demographic Implications of Living Longer

• A population growing rapidly due to natural
  increase has more young people than a stationary
  population.
• Natural Increase
• (Crude Birth Rate - Crude Death Rate)
• Both rapidly and slowly growing countries can
  have a problem with dependency ratio.
• The number of non-working compared to working
  individuals in a population.

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Age Structure Diagrams
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Population Growth Opposing Factors

• Pronatalist Pressures
• Factors that increase the desire for children.
• Source of pleasure, pride, comfort.
• Source of support for elderly parents.
• Current source of family income.
• Social Status
• Replace members in society as they die.
• Boys frequently valued more than girls.

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Birth Reduction Pressures

• Higher education and personal freedom for women
  often result in decisions to limit childbearing.
• When women have more opportunities to earn a
  salary, they are less likely to have children.
• Education and socioeconomic status are usually
  inversely related to fertility in wealthier
  countries.

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Birth Reduction Pressures

• In developing countries, higher income often
  means families can afford more children, thus
  fertility often increases.
• In less-developed countries, adding another child
  to a family usually does not cost much, while in
  developed countries, raising an additional child
  can carry significant costs.

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United States Birth Rate
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DEMOGRAPHIC TRANSITION

• Model of falling death rates and birth rates due
  to improved living conditions accompanying
  economic development.
• Pre-Developed Country - Poor conditions keep
  death rates high, thus birth rates are
  correspondingly high.
• Economic Development brings better conditions and
  standard of living thus death rates fall. Birth
  rates stay constant or even rise.

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Demographic Transition

• Eventually, birth rates begin to fall.
• Populations grow rapidly in time between death
  rates and birth rates fall.
• Developed Countries - Transition is complete and
  both death and birth rates are low and population
  is in equilibrium.

30
Demographic Transition
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Optimism or Pessimism

• Some demographers believe the Demographic
  Transition is already taking place in developing
  countries, and world population should stabilize
  during the next century.
• Others argue that many poorer countries are
  trapped in the middle phase of transition, and
  their populations are growing so rapidly that
  human demands exceed sustainable resource yields.

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Social Justice

• Still other demographers believe that in order
  for the Demographic Transition model to work,
  resources must be distributed more equitably.
• The world has enough natural resources, but
  inequitable social and economic systems cause
  maldistribution.

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FAMILY PLANNING

• Family Planning allows couples to determine the
  number and spacing of their children.
• Birth Control - Any method used to reduce births.
• Traditional Methods
• Long breast-feeding, taboos against intercourse
  while breast-feeding, celibacy, folk medicines,
  abortion, infanticide.

34
Birth Control

• Current Methods
• Avoidance of sex during fertile periods.
• Mechanical barriers preventing contact between
  sperm and egg.
• Surgical prevention of sperm or egg release.
• Chemical prevention of sperm or egg maturation,
  release, or implantation.
• Physical barriers to implantation.
• Abortion

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FUTURE OF HUMAN POPULATIONS

• Most demographers believe the world population
  will stabilize sometime during the next century.
• Projections of maximum population size
• Low 8 billion
• Medium 9.3 billion
• High 13 billion

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Summary

• Population Doubling Times
• Malthus vs. Marx
• Role of Technology
• Two Demographic Worlds
• Fertility and Birth Rates
• Mortality and Death Rates
• Population Growth Factors
• Demographic Transition
• Future of Population Growth

37
Fig. 4.13