2. What Was Earth Like 4 Billion Years Ago?

3. The Mystery of the Late Heavy Bombardment

4. Where Did Earth's Water Come From?

5. How Did Life Begin?

6. What Was The Last Common Ancestor of all Life on Earth?

7. Were Volcanoes The Key To Life?

8. Did Life on Earth Come From Space?

9. What Would The Earth Have Been Like Without Life?

10. What is the Oldest Fossil on Earth?

11. How The Earth Got Its Magnetic Field (And Why It Might Not Protect Us Much Longer)

12. What Was Earth Like 3 Billion Years Ago?

13. How Bad Was The Great Oxidation Event?

14. How Did Life Recover From The First Mass Extinction?

15. What Would The Earth Be Like Without Photosynthesis?

World Without Photosynthesis

16. What Was The First Virus?

Older Than Life? Evolution of Viruses

17. What Is The Other 99.99% Of Life?

4 Billion Years of Life: Tour of the Biosphere

18. What Was The Earth Like 2 Billion Years Ago?

2 Billion Years Ago: After The Great Flood

19. A Tour of Earth's Ancient Supercontinents

Before Pangaea

20. A Tour of Earth's Ancient Superoceans

Exploring Earth's Prehistoric All Sea

21. What Was The "Boring Billion" Really Like?

1.8 to 0.8 Billion Years Ago: Earth's Lost Billion Years

22. What Was The First Complex Life on Earth?

Earth's Impossible Fossils

23. What Was The Earth Like 1 Billion Years Ago?

One Billion Years Ago: Is This Eden?

24. What Was The First Fungus?

The Key to Life? Evolution of Fungi

25. Why Did The Earth Totally Freeze For 100 Million Years?

Snowball Earth

26. Were These The First Animals?

The Ediacaran: Life's Failed Experiment?

27. How Far Back In Time Could You Have Survived On Earth?

How Far Back In Time Could You Have Survived On Earth?