6 - 5.4
5.4 - 4.8
4.8 - 4.2
4.2 - 3.6
3.6 - 3
 
3B
6 - 3 B
600M
25th
6 - 5.75
24th
5.75 - 5.5
23th
5.5 - 5.25
22th
5.25 - 5
21th
5 - 4.75
20th
4.75 - 4.5
19th
4.5 - 4.25
18th
4.25 - 4
17th
4 - 3.75
16th
3.75 - 3.5
15th
3.5 - 3.25
14th
3.25 - 3
 
Precambrian Time 4.5 - 543 M
 
Hadean Eon (Azoic) 4.5 - 3.9
Archean Eon 3.9 - 2.5
 
- 4.5 - 543 M Precambrian Time

- 4 Earliest life appears, possibly derived from self-reproducing RNA molecules. The copying/reproducing/replicating of these molecules requires resources like energy, space and smaller building blocks, which soon become limited, resulting in competition. Natural selection favors those molecules which are more efficient at replication. DNA molecules then took over as the main replicators. They soon develop inside an enclosing membrane which provide a stable physical and chemical environment conducive to their replication - the birth of proto-cells.

Geologic - The Earth forms as a solid planet.
Biologic - No evidence of life yet known.

- 3.9 Cells resembling Prokaryotes appear. Chemoautotrophs using carbon dioxide as a carbon source and oxidize inorganic materials to extract energy. Later, prokaryotes evolve glycolysis, a set of chemical reactions that free the energy of organic molecules such as glucose. Glycolysis generates ATP molecules as short-term energy currency, and ATP continue to be used in almost all organisms unchanged to this day.