Chapter 13: Population Growth

Section 13.2: A Growing Human Population

Many scientists believe that the Earth’s human carrying capacity

is estimated at 4-16 billion.

Many scientists expect the world’s

human population to stabilize around 10

billion people.

Studying the patterns of the past may help us plan for the future.

From Hunting and Gathering to Agriculture

• For 99% of our history, all humans were hunter-gatherers – people who obtain their food by hunting, fishing, and gathering wild plants.

• Today very few live this style.

Hunter-Gatherer Populations

• Usually remained small!• Most lived in groups of

25-50 people.• These people widely

spread out across the landscape.

• Approximately 1 million people lived during this period.

Then about 10,000 years ago, people began to raise animals and grow crops instead of relying on wild animals and

plants.

This change from hunting and gathering to

farming had such a dramatic effect that it is often referred to as the

agricultural revolution.

People probably began to raise crops and animals in many different places at about the same time – but we recognize three places known as the fertile

crescents.

• Mesopotamia – Tigris-Euphrates River Valley in Iraq

• Nile River Valley in Egypt

• Yellow River Valley in China

Results of the transition to agriculture.

• People were able to build permanent shelters.

• Typically they lived near reliable water sources.

• More food was grown than they could ever gather.

• People could now store food for harsh winters and dry summers.

The results of the transition to agriculture permitted the

human population to

explode.

Other reasons for the population boom…

• Farm families needed workers for their fields…so they had more kids!

• Permanent shelter…led to safer living conditions!

• Living around reliable water source meant healthier drinking water and sanitation.

As we progress through the twenty-first century, the human population growth is starting to

slow!

Human population growth is said to occur in three stages:

• Stage #1: Both the birth and death rates are high in pre-industrialized societies.– Population grows very

slowly!

Human population growth is said to occur in three stages:

• Stage #2: When health care improves – birth rates stay high, but death rate drops.– The population begins

to grow rapidly!

Human population growth is said to occur in three stages:

• Stage #3: Birth rates fall until they are roughly equal to death rates.– Population growth

slows down or stops!

Why do birth rates drop during the third stage?

• Women begin to get formal education and enter the workforce – postponing marriage and childbearing.

• Parents realize that their children will most likely reach adulthood – so they want as many children as they can adequately support.

The world is now divided into countries that have and have not

completed the demographic transition.