The Proterozoic Eon, spanning from 2,500 million to 539 million ... Were environmental factors, such as climate and oxygenation, solely responsible, or did evolutionary pressures play a role?

With this new study, the chart of life now includes life forms from the Proterozoic Eon, 2,500 million to 539 ... Was it environmental, such as climate changes and increases in atmospheric oxygen ...

This paper will take you as far back in the climate record as is currently possible, to the Archean Eon, from 3.9 to 2. ... worlds of the Archean, Proterozoic, and much of the Phanerozoic may ...

The Precambrian is usually considered to have three eons: the Hadean, the Archean and the Proterozoic. Some scientists recognize a fourth eon, which they call the Chaotian, which predates the ...