| years ago | date | what happened |
|---|---|---|
| 1,333,333,333 | Dec. 1 | Oxygen begins to be a significant part of Earth's atmosphere... the first ecological catastrophe. Oxygen is a deadly poison to 99% of organisms (anaerobic bacteria) living in Earth at this time. (If there had been an Environmental Protection Agency around, oxygen would have been banned. |
| 1,290,000,000 | ||
| 1,247,000,000 | ||
| 1,204,000,000 | ||
| 1,161,000,000 | ||
| 1,118,000,000 | ||
| 1,075,000,000 | ||
| 1,032,000,000 | Dec. 8 | Second stable system of crustal tectonic plates is established. |
| 989,000,000 | ||
| 946,000,000 | ||
| 903,000,000 | ||
| 860,000,000 | ||
| 817,000,000 | Dec.13 | The Great Light, Phase 7 First truly multicellular organisms... worms |
| 774,000,000 | ||
| 731,000,000 | ||
| 688,000,000 | Dec. 16 | first periods of extensive glaciation |
| 645,000,000 | Dec. 17 | Invertabrates proliferate. |
| 602,000,000 | Dec. 18 | Paleozoic Era begins; oceanic plankton emerge; trilobites |
| 559,000,000 | Dec. 19 | first vertabrates... jawless fish; Cambrian explosion begins |
| 516,000,000 | Dec. 20 | first vascular plants; plants begin to colonize land |
| 473,000,000 | Dec. 21 | Animals emerge from the ocean; first insects |
| 430,000,000 | Dec. 22 | first true amphibians |
| 387,000,000 | Dec. 23 | first trees; first reptiles |
| 344,000,000 | Dec. 24 | first flying insects |
| 301,000,000 | Dec. 25 | thrinaxodon (Permian mammal-like reptile) |
| 258,000,000 | Dec. 26 | first true mammals; break-up of Pangaea begins; Mesozoic Era begins; late Permian extinction... 95% of sea life and most land life is wiped out |
| 215,000,000 | Dec. 27 | first birds |
| 172,000,000 | Dec. 28 | first flowers; first dinosaurs; Atlantic Ocean begins to open up between South American and Africa |
| 129,000,000 | Dec. 29 | The Age of Dinosaurs Begins |
| 86,000,000 | Dec. 30 | Dinosaurs extinct; mammals flourish; first primates; first cetaceans; Cenozoic Era |
| 43,000,000
today |
Dec. 31
Jan. 1 |
See Cosmic Day (December 31) Go back to The Cosmic Year) |