Understand how people may have first reached the Americas. Find out how people learned to farm.

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 bridgein 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 thatpeople 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 ofcivilization.

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

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

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.

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