To fill in the question marks in your timeline of human migrations, it is important to understand the chronological order of key migrations of Homo sapiens from Africa.
- 200,000 years ago: Homo sapiens appear in Africa.
- 40,000 years ago: Homo sapiens arrive in Europe.
- 20,000 - 60,000 years ago: They migrate to Asia. (Note: The date range for migration to Asia is broad, but it is generally accepted that they spread into Asian regions during this timeframe.)
- 15,000 years ago: The earliest evidence suggests that Homo sapiens arrive in the Americas.
After considering the established chronology of migrations, the most appropriate response for the question marks would be:
- arrive in Asia; arrive in the Americas.
So, the completed timeline would be:
- 200,000 years ago: appear in Africa
- 40,000 years ago: arrive in Europe
- 20,000 - 60,000 years ago: arrive in Asia
- 15,000 years ago: arrive in the Americas.