10 Most Important Events

Early bacteria

Early bacteria formed during the Precambrian; during this time the oceans formed and covered most of the earth 4 billion years ago.

Oxygen levels rise

Oxygen levels rise, because plants use photosynthesis.


Invertebrates first appear during the Cambrian period.

Coral reefs

Coral reefs developed during the Silurian period.

Winged insects

Winged insects appear in the Pennsylvanian period.


Pangaea is the earliest supercontinent; it formed during the Permian period.


Reptiles take over land during the Permian period.


The first dinosaurs appear during the Triassic period.


First humans "evolve" in Africa 100,000 years ago.