4550 Ma:HominidsMammalsLand plantsAnimalsMulticellular lifeEukaryotesProkaryotesHadeanArcheanProterozoicPaleozoicMesozoicCenozoic4527 Ma: Formation of the Moon4.6 Ga4 Ga3.8 Ga3 Ga2.5 Ga2 Ga1 Ga542 Ma251 Ma65 Maca. 4000 Ma: End of the Late Heavy Bombardment; first lifeca. 3500 Ma: Photosynthesis startsca. 2300 Ma: Atmosphere becomes oxygen-rich; first Snowball Earth750-635 Ma: Two Snowball Earthsca. 530 Ma: Cambrian explosionca. 380 Ma: First vertebrate land animals230-65 Ma: Dinosaurs2 Ma: First Hominids