Human Population History

LOSSES: Mortality and Emigration Mortality - Death Rate.

Survivorship - Percentage of cohort surviving to a certain age.

Life expectancy - Probable number of years of survival for an individual of a given age.

Increases as humans age. Life Span - Longest period of life reached by

a given type of organism. Emigration - Movement of individuals

out of a population.

Given a long list of possible factors promoting growth, for a specific case,

what leads to overpopulation or extinction?

Identify most likely influences (create a simplified “model”)

Test the predictions of the model

Changing birth rates: opposing factors Factors that increase the desire for

children Personal

Source of pleasure, pride, comfort. Source of support for elderly parents. Current source of family income. Social Status

Government policy Labor availability Tax and social welfare balances

Birth Reduction Pressures Good times

Education and socioeconomic status are usually inversely related to fertility in wealthier countries.

Higher education and personal freedom for women often result in decisions to limit childbearing

When women have more opportunities to earn a salary, they are less likely to have children

Bad times Food & violence uncertainty

Infant Mortality and Women’s Rights

Fig. 9.10

Birth Rates in the United States

Fig. 9.11

Fig. 9.12

Fig. 9.13

Population “momentum”

DEMOGRAPHIC TRANSITION Model of falling death rates and birth

rates due to improved living conditions accompanying economic development. Pre-Modern Society - Poor conditions

keep death rates high, thus birth rates are correspondingly high.

Economic Development brings better conditions and standard of living thus death rates fall. Birth rates stay constant or even rise.

Demographic Transition Eventually, birth rates begin to fall.

Populations grow rapidly in time between death rates and birth rates fall.

Developed Countries - Transition is complete and both death and birth rates are low and population is in equilibrium.

But is this hypothesis accurate?

Demographic Transition

Fig. 9.15

http://www.ted.com/talks/lang/eng/hans_rosling_shows_the_best_stats_you_ve_ever_seen.html

What are the consequences of large numbers of people?

Pessimistic View

Optimistic View

Questions for discussion What defines human “carrying

capacity”? How do these factors change birth or

death rates to stabilize population size?

For national policy makers around the globe, what should be considered in setting policy about birth rates?

…the U.S. can be called the most over-populated nation.

Erhlich & Ehrlich, Environmental Law (vol. 27, no. 4) 1997

If every one of the 6 billion of us lived in Texas…room enough for

each family of four to have a house and 1/8 acre…

Moore, National Review (Oct. 25, 1999)

…the answer often focuses on crowding…these views miss the

point…

Erhlich & Ehrlich, Environmental Law (vol. 27, no. 4) 1997

…energy use seems to be a priori a reasonable measure…

Erhlich & Ehrlich, Environmental Law (vol. 27, no. 4) 1997

Life expectancy is the best overall numerical measure of human

well-being

Moore, National Review (Oct. 25, 1999)

Population growth is a sign of mankind’s greatest triumph - our

gains against death

Moore, National Review (Oct. 25, 1999)

It’s hard to argue with somebody who despairs because mankind is alone at the top of the food chain.

Moore, National Review (Oct. 25, 1999)

…the key is regulation of birth rates…

Erhlich & Ehrlich, Environmental Law (vol. 27, no. 4) 1997

capitalism is by far the best contraceptive

Moore, National Review (Oct. 25, 1999)

Assuming human progress and scientific advancement continue as they have…

…12 billion people will be richer, healthier and better fed than the 6 billion of us today…

Moore, National Review (Oct. 25, 1999)

In a rational world, Malthusianism would be [in]…thorough disrepute…every

objective trend is running in precisely the opposite direction…

Moore, National Review (Oct. 25, 1999)

By assaulting the earth’s ecosystems, humanity is…sawing off the limb on which it perches.

Erhlich & Ehrlich, Environmental Law (vol. 27, no. 4) 1997

"We now have in our hands—really, in our libraries—the technology to feed, clothe,

and supply energy to an ever-growing population for the next seven billion years."

Simon, The Ultimate Resource, 1981

"There is no reason to believe that at any given moment in the future the

available quantity of any natural resource or service at present prices will be much smaller than it is now,

or non-existent."

Simon, The Ultimate Resource, 1981

Paul Ehrlich and Human Populations

Why is zero population growth counter to Natural Selection?