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Human Populations. POPULATION GROWTH. Until the Middle Ages, human populations were held in check by: - diseases - famines - wars Took all of human history to reach 1 billion 150 years to reach 3 billion 12 years to go from 5 to 6 billion
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POPULATION GROWTH • Until the Middle Ages, human populations were held in check by: - diseases - famines - wars • 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. Populations grew slowly
Human Population Growth Exponential Growth Curve
LIMITS TO GROWTH • Thomas Malthus (1798) - human populations tend to increase exponentially while food production is plentiful. • Humans will outstrip food supply and eventually collapse. • Human population only stabilized by positive checks. • Humans are too lazy and immoral to voluntarily reduce birth rates.
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.
HUMAN DEMOGRAPHY • Demography births, deaths, distribution, and population size. • The current U.S. Census Bureau estimate for world population is ~ 7.4 billion.
Two Demographic Worlds • 1) poor, young, and rapidly growing. • Developing Countries • Africa, Asia, Latin America, India, China • Contain 80% of world population, and will account for 90% of projected growth. • 2) wealthy, old, and mostly shrinking. • Developed Countries • North America, Western Europe, Japan • Average age is about 40. • Populations expected to decline.
Age Structure Developing Developed
Emigration and Immigration • Emigration and immigration play a large role in human population dynamics. • Immigration is a controversial issue. “Guest workers” often perform dangerous or disagreeable work, while being paid low wages with few rights. • Locals complain immigrants take away jobs and overload social services.
Birth Reduction Pressures • Higher education and personal freedom for women = less children born • More opportunities to earn a salary = less likely to have children • Education and socioeconomic status are usually inversely related to fertility in wealthier countries.
Birth Reduction Pressures • In developing countries, higher income = 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.
p. 149 Demographic Transition
FAMILY PLANNING AND FERTILITY CONTROL • 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.