Approximate Ages of Events in Years Before the Present

	Approximate Ages of Events in Years Before the Present
	How Do We Know: Ancient Environments
	Life in Lucy's Time

1. Oldest known rocks and fossils, 3.8 billion years ago.
2. First known plants (algae), 3.2 billion years ago.
3. First known animal (jellyfish), 1.2 billion years ago.
4. Beginning of the Cambrian and first abundant fossils, 550 million years ago.
5. Beginning of the Ordovician and first backboned animals, 500 million years ago.
6. Beginning of the Silurian and the first land plants, 440 million years ago.
7. Beginning of the Devonian and the first amphibians, 400 million years ago.
8. Beginning of the Mississippian, 350 million years ago.
9. Beginning of the Pennsylvanian and the first reptiles, 305 million years ago.
10. Beginning of the Permian, 285 million years ago.
11. Beginning of the Triassic and first dinosaurs, 245 million years ago.
12. Beginning of the Jurassic and first mammals, 205 million years ago.
13. First birds, 150 million years ago.
14. Beginning of the Cretaceous, 140 million years ago.
15. Beginning of the Paleocene and first primates, 65 million years ago. Dinosaurs become extinct.
16. Beginning of the Eocene, 60 million years ago.
17. Beginning of the Oligocene and first elephants, 35 million years ago.
18. Beginning of the Miocene, 25 million years ago.
19. Beginning of the Pliocene, 5 million years ago.
20. First humanlike animals, 2 million years ago.
21. Beginning of the Pleistocene and ice ages, 1 million years ago.
22. Last ice age, 10,000 years ago. Beginning of the Holocene.