🧬 Life
▪️ Oxygen fills atmosphore 2.4 BYA
🧊 Huronian Ice Age 2.4 – 2.1 BYA
▪️ Oldest (eukaryotic) fossils (algae) 1.7 BYA
▪️ Development and physiology (multicellularity) 1 BYA
🧊 Cryogenian Ice Age 850-635 MYA
▪️ Oldest animal fossils 750-550 MYA
▪️ Cambrian Explosion 540 MYA