2. 4B - earliest life appears
3.9B - photosynthesis
3.8B - last common ancestor for all living organisms
3.5B - first multicellular organisms
1.2B - sexual reproduction evolves, leading to faster evolution
1.5B - plants
600M - first eyes
550M - first brain(flatworm)
540M - heart/liver organ(worm), gills in fish ancestor
480M - first gilled fish; distant of all living fish
300M - reptiles reproducing out of water
256M - mammal-like reptiles
220M - mammals
125M - non-egg laying mammals(live birth)
85M - primates evolve out of mammals
(Cretacious epoch, during dinosaur times)
28M - apes; tailless primates
