1. Human Populations

2. Until the Middle Ages, human populations were held in check by:
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

3. Human Population Growth
Exponential Growth Curve

4. 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.

5. 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.

6. Malthus and Marx

7. Human Population Density

8. HUMAN DEMOGRAPHY
Demography
births, deaths, distribution, and population size.
The current U.S. Census Bureau estimate for world population is ~ 7.4 billion.

9. 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.

10. Age Structure
Developing
Developed

11. 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.

12. 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.

13. 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.

14. Birth Rates in the United States

15. Demographic Transition

16. 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.