Origin
| Evolution | Years Ago |
|---|---|
| Earth | 4,600 million |
| Life on Earth | 3,800 million |
| Photosynthesis | 2,300 million |
| Eukaryotic cells | 1,400 million |
| Sexual reproduction | 1,100 million |
| Metazoans | 700 million |
| Land plants | 400 million |
| Land animals | 350 million |
| Mammals | 200 million |
| Man | 2 million |
- World Out of Balance: Our Polluted Planet, Jon Ericson
