A Brief History of the Earth. Timescale. 7/8 of the entire period life has existed on earth is known as the Precambrian era. During this era, life was largely single celled, and prokaryotic. Other Eras. Following the Precambrian era came the Paleozoic, Mesozoic , & Cenozoic eras.
Following the Precambrian era came the Paleozoic,Mesozoic, & Cenozoic eras
The Giant Orthocone
Some early mammals survived the cataclysm.
These would be the ancestors to all living mammals.
Mammals weren't the only survivors, there was of course….