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Human population and demographics
- 1. Think of theearth as a living organism that is being attacked by billions of bacteria whose numbers double every forty years. Either the …bacteria dies, or both die. - Gore Vidal
- 2. During theearliest parts of human history, our population survived as hunter-gatherers. The population during this time was low; estimated to be in the thousands. Like other species, population size was limited by environmental resistance factors, such as competition for food and water, predators, and disease. 2
- 3. At somepoint, estimated to be about 130,000 years ago, Homo sapiens migrated out of Africa into what would become the fertile crescent. 3
- 4. The fertilecrescent, as a “bridge” between Africa and Eurasia, had an unusually high amount of biodiversity. The eight “founder crops,” including wild ancestors to modern flax, wheat, barley, and lentils, grew here. The ancestor species of four out of the five modern domesticated livestock animals were native to here. 4
- 5. The presenceof two major river systems also stimulated the invention of irrigation. This period is known as the Agricultural Revolution and marked the first point where humans moved from a nomadic lifestyle to settling in towns and villages. Instead of hunting and gathering, humans began growing and raising their own food supply. 5
- 6. Agriculture gavehumans a greater degree of control over their food supply. As a result, the population began to grow. 6
- 7. The humanpopulation grew at a steady rate, reaching about 800 million by 1800 A.D. Some density-dependent limiting factors were still in place. Famines Western Europe, 400-800 A.D. Mayan Civilization, 800-1000 A.D. Little Ice Age, 17th century Great Potato Famine (Ireland), 1845-1847 Disease Malaria (10,000 B.C.-present), cause of about half of all human deaths Black Plague (14th century), Eliminated 1/3 of Europe’s population. 7
- 8. The industrialrevolution began a multitude of new technologies and innovations. Electricity The steam engine Water treatment Antibiotics Vaccines The overall impact was a massive drop in infant mortality – the death rate in newborns. This led to an increase in overall average life expectancy. Pre-industrial life expectancy in Britain was 25-40 years. Current life expectancy worldwide is 67 years. 8
- 9. Industrialized farming,water treatment, and modern medicine removed many density- dependent limiting factors. The human population began to grow exponentially. 9
- 10. 10 Exponential growthoccurs when the population size and its rate of growth both increase. It took over 70,000 years to reach 1 billion. 150 years to reach 3 billion. 25 years to reach 4 billion. 20 years to reach 5 billion 12 years to reach 6 billion. 11 years to reach 7 billion.
- 11. Another wayof measuring growth is through doubling time, an estimate of how long it will take the population to double in size at its current rate of growth. Doubling time is calculated with this equation: 70 / (Current % Growth Rate) 11 Year Growth Rate Doubling Time 1970 2.09 34 years 1980 1.82 38 years 1990 1.60 44 years 2000 1.26 56 years 2010 1.12 63 years
- 12. 12 Demographics isthe study of human populations. Includes comparing statistics such as births, deaths, gender, race, and economic status. Developing countries have populations that tend to be poorer, younger, and are growing much more rapidly. Developed countries are wealthy, old, and tend to have decreasing population sizes.
- 13. Developing countriescontain 80% of the world’s population, and will account for 90% of its projected growth. 13
- 14. Comparing developedand developing countries requires the use of these demographic variables: Life expectancy, or how long an average newborn will live in a society. Most affected by infant mortality rate. The total fertility rate, the average number of children a woman will have in her lifetime. A fertility rate above replacement level, 2.1, will generally result in a growing population. Below replacement level results in a shrinking population. Gross domestic product per capita is a measurement of standard of living. Total value of all goods and services produced in a country per person. 14
- 15. Afghan market. Photoby Staff Sgt. Russell Lee Klika 15 Country GDP Per Capita Total Fertility Rate Life Expectancy United States $53,041 1.88 79 Afghanistan $664 5.14 51.28
- 16. Life expectancy(and infant mortality) are highly correlated with GDP, up to about $4000/year. 16
- 17. The movementof individuals between areas can have a major impact on population change. Emigration is when people move out of an area. More likely to occur in developing countries. Immigration is when people move into an area. More likely to occur in developed countries. 17
- 18. In somedeveloped countries, immigration offsets or delays the normal population decline. The United States total fertility rate in 2011 was 1.89, below replacement level. The overall immigration was over 11 million. The population growth rate was 0.7%. Japan had a fertility rate of 1.39 in 2011. The overall immigration was just over 200,000. Their population growth rate is -0.2%. 18
- 19. When studyingthe demographics of a single country, two of the most important factors to examine are gender and age distribution. These variables are graphed as population pyramids, and can provide valuable insight into a country. 19
- 20. What isthe overall shape of the graph? Is there a dominant age group or groups? What proportion of the 0-4 age group survives into the elderly (60+) age groups? Are the male and female sides roughly equal? 20
- 21. The fertilityrate and population growth patterns in a given country will not remain constant. They change based on a wide variety of factors. 21 United States Fertility Rates, 1911-2011
- 22. Countries willtypically pass through a series of stages as they industrialize and transition from developing to developed countries. During the pre-industrial stage, food shortages, malnutrition, poor sanitation, and lack of access to modern medicine keep death rates high. All regions of the world were in this stage up until the industrial revolution. 22
- 23. During theearly transition stage, access to food and medicine improve, leading to a rapid drop in death rates. Birth rates remain high, as family size is tied to cultural norms and religious beliefs. Population size begins to increase exponentially. 23
- 24. During thelate transition stage, efforts are made to reduce birth rate. Birth control and sex education gain greater acceptance. Women play a greater role in family planning. The population continues to increase, but more slowly. 24
- 25. During theindustrial stage, birth rates have fallen back into balance with death rates. Total fertility rate is close to replacement level. The population stabilizes. 25
- 26. During thepost-industrial stage, birth rates continue to fall due to the pressure to not have a child. Total fertility rate is below replacement level. The population size decreases. 26
- 27.
- 28. 28 Most demographersbelieve 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
- 29.