Sophia's online courses not only save you money, but credits are also eligible for transfer to over 2,000 colleges and universities.*
The archean age was a period of time 2,500-3,800 million years ago. The oldest rocks formed on earth were produced during the archean age. During the archean age, the oxygen level of the earth increased and the very first cells lived during this time. The first photosynthesis on earth began roughly 3,500 million years ago. Fossils of simple organisms, like bacteria, are present from the archean age.