1. Objectives Understand how people may have first reached the Americas.
Find out how people learned to farm.
Explore the civilizations of the Mayas, Aztecs, and Incas.

2. Terms and People glacier – thick sheet of ice
irrigate – to water crops by channeling water from rivers or streams
surplus – excess; quantity that is left over
civilization – an advanced culture in which people have developed cities, science, and industries

3. How did early civilizations develop in the Americas?
Scientists have several theories about how people first came to the Americas.
One theory says people migrated over a land bridge.
One theory says people came by boat.

4. Between 10,000 and 100,000 years ago, much of the world was covered by glaciers.
As more of the world’s water froze, the level of the oceans dropped, and a land bridge appeared between Siberia and Alaska.
Today, that land bridge lies under a narrow waterway called the Bering Strait.

5. Many scientists think people first came to North America between 20,000 and 30,000 years ago.
They believe that hunters crossed the land bridge in pursuit of animals such as the woolly mammoth.

6. Over thousands of years, people spread across
North and South America.

7. The coastal-route theory says that people crossed the arctic waters by boat and traveled southward along the Pacific coast.
Many Native American groups dismiss both theories in favor of their own creation stories.

8. For centuries, early humans could fill most of their needs by hunting, but then many of the larger animals began to disappear.
Hunters became gatherers, traveling around and searching for wild plants and small game.
hunters
gatherers

9. About 8,000 years ago, gatherers in Mexico began growing food, including squash and lima beans.
This discovery of farming meant that families no longer had to wander in search of food.
Farmers began to irrigate and learned to raise animals.

10. The population grew rapidly, and once they began to produce surplus food, Native Americans started trading with others.
Some farming communities grew into cities, which became centers of government and religious life.
With the development of cities came the beginnings of civilization.

11. Over the centuries, several civilizations rose and declined in the Americas:
the Mayas
the Aztecs
the Incas

12. The Mayas Time Period Between A.D. 250 and A.D. 900 Location
Present-day Mexico and Central America
Achievements
Built splendid cities
Developed arts, a system of government, and a written language
Created the most accurate calendar known until modern times

13. Around A.D. 900, the Mayas began to abandon their cities, perhaps because of disease or overpopulation.

14. The Aztecs Time Period Between 1325 and 1521 Location
Present-day Mexico
Achievements
Built the city Tenochtitlán, which may have been the biggest city in the world at the time
Built Tenochtitlán on islands in a large lake and connected them by stone roadways

15. On a series of islands in a large lake, the Aztecs built a great capital city, Tenochtitlán, on the site of present-day Mexico City.

16. Tenochtitlán Population
More than 200,000 people lived there at the city’s height.
Farming
Many farmers raised crops on floating platforms.
Religion
Religion dominated Aztec life.
The center of the city had dozens of temples that honored Aztec gods.
The Aztecs practiced human sacrifice as an offering to their gods.

17. During the 1400s, Aztec armies brought half of modern-day Mexico under their control.
The Aztecs were harsh rulers, and their subjects would eventually turn on them when Europeans came to conquer the region.
Aztecs
Europeans
subjects

18. The Incas Time Period Between the early 1400s and 1533 Location
Down the coast of South America along the Andes, across the Atacama desert, and to the fringes of the Amazon rain forest
Achievements
Built the largest empire in the world in the 1400s
Buildings of huge stones shaped to fit together
Roads, walls, canals, and bridges
Fine weavings and metalwork

19. Section Review
QuickTake Quiz
Know It, Show It Quiz 19