1. Human Populations
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2. Human Populations Flourish
Over 6 billion people
Long before humans evolved, over 1 million years ago, early ancestors could walk upright
About 100,000 years ago, anatomically modern humans were spreading across the globe
By 12,000 years ago, we had inhabited all the world’s major landmasses (except Antarctica) and numbered around 5 million
As hunter-gatherers, we could not increase quickly in number

3. Change to agriculture
One of the most profound changes in human history came with the intentional planting of seeds and the beginning of agriculture
Human populations became stationary
Having large families was now possible
Much higher population densities could be supported
Fewer people were required to work to meet day-to-day survival requirements, so had time to become specialized artisans, scholars and merchants
Those human populations that experienced rapid growth based on large agricultural surpluses began to spread out across the globe

4. Impact of Disease
The establishment of large sedentary human populations had a profound effect on the evolution of pathogens
Epidemic: any disease that spreads rapidly through a population (usually only when densities are high)
Many diseases (e.g. TB, influenza) believed to be diseased of domestic animals that evolved to infect humans
Europeans brought diseases to America to which Aboriginal people had little or no resistance

5. Impact of Science & Medicine
In the 17th century, science-based knowledge and technology started to become major influences on society
Our understanding of and interaction with the natural world revolutionized
Cell and germ theories led to modern medicine
Industrial Revolution: mass production of goods
Another significant increase in food supply and reduction of people needed to work on the land
Death rates dropped and populations became increasingly urbanized
Population doubling time began to rapidly shrink as the population exploded, reaching 1 billion in 1850

6. Human Population Growth

7. Human Demographics
Demography: the study of human populations (growth rate, age structure, and other characteristics)
Currently, rates are about births per 1000 individuals and 13 deaths per 1000, per year.
Average growth rate is 16 per 1000, or 1.6%
This represents an increase of about 96 million people per year, or per day!

8. Population Growth Rate

9. Population Pyramids
Age pyramids, from left to right: Rapid Growth, Slow Growth, Zero Growth, Negative Growth
Yellow = post-reproductive year; orange = reproductive years; red = pre-reproductive years

10. Demographic Transition Model
The only factors that dramatically influences human population growth are birth and death rates
This model describes the relationship between economic development and population patterns

11. Gross National Product (GNP)
Gross National Product (GNP): total value of all goods and services produced by a country in one year
Often used as an index of a country’s level of industrialization
E.g. the per capita GNP of the USA is $23,120
the per capita GNP of Ethiopia is $110

12. Future Trends
Many scientists over the years have predicted that as Earth’s population continues to grow, we will deplete the planet’s resources and result in global famine and other ecological crises.
Improvements in food technology and access to potable water have prevented any previously-predicted global famines
Does Earth have the capacity to sustain an ever-growing population? What will happen? What challenges do we face?