Human Populations

Human Populations

Big Question

  • How did humans avoid density-dependent factors that limit population growth?
  • Humans learned to:
    • Communicate
    • Make tools
    • Control fire
  • These abilities allowed humans to inhabit environments previously uninhabitable.

Hunter-Gatherers

  • Nomadic lifestyles:
    • No permanent residence
    • Biological and social restrictions on family sizes
    • Low birth rate
    • High death rate

Agricultural Revolution

  • Humans discovered plants and animals suitable for cultivation and domestication.
  • Larger families became possible due to agricultural practices.
  • Supported larger population densities.

Intellectual Revolution

  • Specialization of labor:
    • Artisans
    • Scholars
    • Merchants
  • Establishment of political organizations
  • Major advances in technology
  • Rapid population growth:
    • Spread across the globe
    • Displaced indigenous people
    • Brought plants, animals, guns, steel, and diseases

Industrial Revolution

  • Increasingly urbanized populations
  • Increased food production with fewer people working the land
  • Vaccines, medicine, sanitation, and safe drinking water
  • Decreased mortality rates

Mortality Rates

  • Mortality is the death rate per individual.
  • Death rate has been continuously dropping in the developing world due to:
    • Personal hygiene
    • Improved sanitation
    • Modern medicine
    • Development of antibiotics

Avoiding Natural Limits

  • Humans avoided natural growth limits through:
    • Reduced competition for space by expanding geographic range
    • Reduced competition for food by shifting from hunting/gathering to agriculture to industrialization
    • Reduced effect of disease with advances in public health

Historical Population Growth

  • Lack of large fluctuations associated with famines or wars, except for:
    • The "black death" or plague in Europe, which caused a small downward spike.

Human Demographics

  • Demography: study of human populations.
  • Relies on:
    • Data collection
    • Statistical analyses
    • Theoretical models
  • Birth rates have remained relatively constant.
  • Death rates have dropped dramatically, leading to a doubling time of approximately 43 years.

Fertility vs. Literacy

  • Population growth is driven by fertility (birth rate).
  • More developed countries have lower fertility rates, suggesting a link between fertility & literacy.
  • In rural areas, large families have an economic advantage due to physical labor.

Fertility & Literacy

  • As technology improves, parents realize more children decreases their standard of living.
  • Thailand Example:
    • Economic status linked to secondary schooling.
    • Parents paid for education.
    • Fertility rate decreased from 6 to 2 children per couple in a decade.

Future Population Projections

  • U.N. projections based on women having 2.5 (high), 2.0 (medium), or 1.5 (low) children on average.

Growth Rates

  • Growth rates vary in different regions due to differences in age structure.
  • The number of people under 15 is a major factor in a country’s future population growth.

Demographic Transition Model

  • Model describing stabilized population growth in developed nations over the last century.

Stage 1: Preindustrial

  • High birth rates and high death rates.
  • Little to no modern medicine or hygiene.
  • Agriculture with low yields.
  • Examples: Sudan, Ethiopia
  • Stable population due to little surplus food.

Stage 2: Transitional

  • Improved hygiene and modern medical techniques.
  • Decreasing death rate.
  • Significant upward trend in population size.
  • High birth rate due to agricultural economy.
  • Agricultural surpluses lead to urbanization as farms can feed distant populations.
  • Birth rate declines slightly.
  • Examples: Kenya, Mexico

Stage 3: Industrial

  • Urbanization has occurred.
  • Parents are discouraged from having large families due to the rising cost of living.
  • Drop in birth rates, closing to death rate.
  • Increasing population leads to migration and colonization.
  • Birth rate drops as more people choose small families.
  • Death rate drops due to food and health care advances.
  • Population continues to grow.
  • Examples: Brazil, India

Stage 4: Post-Industrial

  • Birth and death rates are low and stable.
  • Higher standard of living.
  • Population growth approaching zero.
  • Developed world remains in this stage.
  • Birth rate falls even more as smaller families become the rule.
  • Death rate is steady.
  • Population starts to decrease.
  • Examples: Canada, Europe

Impacts of Human Population on Nature

  • Reduced biodiversity
  • Increased primary productivity
  • Increased genetic resistance in pests
  • Eliminated natural predators
  • Introduced harmful species
  • Unsustainable use of renewable resources
  • Interfered with chemical cycling and energy flow
  • Relied on fossil fuels

Food and Soil

  • Increased need for food production with population growth.
  • Enough food is produced globally, but distribution is uneven.
  • Millions suffer from starvation and undernourishment.
  • Some regions have fertile soils and favorable climates, while others have poor soil conditions.
  • Drought, flooding, and other harsh conditions limit food production.

Food Sources

  • Agricultural Land:
    • Conversion to non-agricultural uses (housing, industry)
    • Soil degradation due to deforestation and salinization.
  • Livestock:
    • Forest degradation due to ranching
    • 36% of world’s grain goes to feed livestock
    • Livestock wastes pollute waterways
  • Ocean Fisheries
    • Overfishing has depleted stocks beyond sustainable yields
    • Populations may not recover

Strategies for Ensuring Adequate Nutrition

  • Increase the number of new food crops from a diversity of plant species.
  • Distribute food more equitably.
  • Increase land dedicated to grain production.
  • Assist developing countries in efficient crop irrigation systems.

1994 Global Summit on Population & Development

  • Encouraged action to stabilize population at 7.8 billion by 2050.
  • Provide universal access to family-planning services
  • Improve the health care of infants, children & pregnant women
  • Encourage development of national population policies
  • Improve the status of women by expanding education & job opportunities
  • Increase access to education for girls
  • Increase men’s involvement in child-rearing responsibility & family planning
  • Take steps to eradicate poverty
  • Reduce & eliminate unsustainable patterns of production & consumption