Establish Prior Knowledge
Ask students to share what they know about the humans that first settled the Americas. Point out that scientists have long debated about where and when the first humans came to the North American and South American continents. Tell students that in the Snapshot they are about to see, genetic evidence is being used to support one theory.
Have students view the Snapshot and read the synopsis. Have students work in teams to research and report on the following topics.
- What genetic evidence is there for a single main migration across the Bering Strait?
- What other theories have been proposed for human migration to the Americas?
- How did people migrate to South America?
When teams have completed their research, call on them to share what they have learned. Use the following questions to guide further discussion.
1. Which of the theories do you believe to be the correct one?
2. What evidence supports that theory?