Timeline of life on Earth

~2.5 Gya Continents begin to form -carbonate silicate cycle begins to function Oxygen accumulation reaches critical level -oceans rust, iron oxide falls to the bottom -ozone layer forms -most cells incapable of detoxifying oxygen die out Eukaryotes capable of oxygen metabolism proliferate
~1.7 Gya First Multicellular Organisms
~670 Mya First nervous systems First land plants

~2.5 Gya Continents begin to form -carbonate silicate cycle begins to function Oxygen accumulation reaches critical level -oceans rust, iron oxide falls to the bottom -ozone layer forms -most cells incapable of detoxifying oxygen die out Eukaryotes capable of oxygen metabolism proliferate