Chapter 3 Human Population
Introduction
3-1 Human population history
3-2 Social mechanisms of population regulation
3-3 The population explosion and quality of life
Introduction
1. Human population increase:
(1) First humans (Homo habilis 巧人) appeared in Africa 3 million years ago.
(2) Humans (Homo erecturs 直立人) expanded their populations through
Europe and Asia at least a million years ago.
(3) Human (Homo sapiens 智人) appeared in Africa about 1.3 million years ago,
and extended its population to Europe, Asia and Australia about
40,000-50,000 years ago.
2. 1700 AD, 600 million people; 2000, 6 billion people. Why???
3. Answer: agricultural revolution and industrial revolution.
3-1 Human population history
1. From hunting and gathering to agriculture
(1) Before the agricultural revolution: hunting and gathering (fig. 3.1a)
(2) Agricultural revolution:
a. Appeared about 12,000 years ago in the Middle East.
b. Domesticated some of the plants and animals.
c. Carrying capacity for humans increased (fig. 3.1b)
(3) Why did humans wait so long to develop agriculture? Climate change?
(4) Human populations increased with agriculture (fig. 3.2)
(5) New improvements in food production vs. carrying capacity (fig. 3.3)
(6) Population pressure: motivated people to develop additional improvements.
As a feedback loop between population and technology.
(7) No free lunch: more effort for human consumption (fig. 3.4)
(8) Exponential population growth (fig. 3.5)
2. The industrial revolution
(1) Mechanization: more ability to change ecosystems. People were able to
capture a much larger percentage of the ecosystem’s biological production.
(2) Death rates reduced drastically in industrializing countries.
(3) Human population: developing vs. developed countries (fig. 3.6)
(4) Population “ageing” is a major issue in developed countries.
(5) Migration from developing countries to seek better economic opportunities.
3. The green revolution
(1) Green revolution: used modern plant breeding to create high-yield varieties
of food to increase carrying capacity for human. (fig. 3.7)
(2) Irrigation was expanded. More food production meant more work.
(3) Genetically modified crops and livestock could increase food production.
(4) Unsustainable: irrigation, water, environmental cost, fertilizer, energy, …
(5) Biological production controlled by humans (fig. 3.8)
3-2 Social mechanisms of population regulation
1. Carrying capacity
(1) An upper limit that food supply places on all populations.
(2) Predation regulates animal population. Wolves vs. deer.
2. Social mechanisms to prevent overpopulation
(1) Birds select mates for reproduction.
(2) Each breeding pair sets up a territory enough to provide food.
(3) Birds have feedback mechanisms to reduce their egg production.
(4) Monkey and apes live in groups and exclude all other individuals.
3. Human society
(1) Negative feedback loops for social control of human population (fig. 3.9)
(2) Traditional population regulation
a. Breast-feeding makes a major contribution to birth control.
b. Marriage: only one son to inherit the family property which could afford
to marry. Similar to birds with territory.
c. Infanticide: boy vs. girl
(3) Territorial conflict: human population regulation.
(4) Territoriality: human behavior. Large nation vs. small nation. Modern
weapons and well-organized armies.
3-3 The population explosion and quality of life
1. Human population explosion
(1) Natural resources are not enough for so many people.
(2) Housing, safe water supply, garbage collection, sewage disposal, …
2. Overpopulation: positive feedback loop of inadequate food supply and
inappropriate land use
3. Environmental refugees: migrate to another region. Ex: rural to urban.
4. Social costs, economic equality, …
5. Overpopulation increases competition for limited resources. Wars.