Human Populations

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

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.

Malthus and Marx

Human Population Density

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.

Birth Rates in the United States

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.