The Precambrian Supereon is divided into three Precambrian eons: the Hadean (4500-3950 Ma), Archean (4000-2500 Ma) and Proterozoic (2500-541.0 ± 1.0 Ma).
3800 Ma and earlier.
4600 Ma > The planet Earth forms from the accretion disc revolving around the young Sun; complex organic molecules necessary for life may have formed in the protoplanetary disk of dust grains surrounding the Sun before the formation of the Earth.
4500 Ma > According to the giant impact hypothesis the moon is formed when the planet Earth and the planet Theia collide, sending a very large number of moonlets into orbit around the young Earth which eventually coalesce to form the Moon. The gravitational pull of the new Moon stabilises the Earth's fluctuating axis of rotation and sets up the conditions in which life formed.
4100 Ma > The surface of the Earth cools enough for the crust to solidify. The atmosphere and the oceans form. PAH infall, and iron sulfide synthesis along deep ocean platelet boundaries, may have led to the RNA world of competing organic compounds.
4500-3500 Ma > The earliest life appears, possibly at Alkaline vents with the creation of the Last Universal Common Ancestor, possibly derived from self-reproducing RNA molecules. The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition, with natural selection favouring those molecules which are more efficient at replication. DNA molecules then take over as the main replicators and these archaic genomes soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: proto-cells.
4000 Ma > Formation of Greenstone belt of the Acasta gneisses of the Great Slave Region, in Canada, the oldest rock belt in the world.
3900 Ma > Late Heavy Bombardment: peak rate of impact events upon the inner planets by meteoroids. This constant disturbance may have obliterated any life that had evolved to that point, or possibly not, as some early microbes could have survived in hydrothermal vents below the Earth's surface; or life might have been transported to Earth by a meteoroid.
3900-2500 Ma > Cells resembling prokaryotes appear. These first organisms are chemoautotrophs: they use 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 and store it in the chemical bonds of ATP. Glycolysis (and ATP) continue to be used in almost all organisms, unchanged, to this day.
3800 Ma > Formation of Greenstone belt of the Isua complex of the western Greenland Region, whose rocks show an isotope frequency suggestive of the presence of life.
3800 Ma – 2500 Ma
3500 Ma > Lifetime of the last universal ancestor; the split between bacteria and archaea occurs.
Bacteria develop primitive forms of photosynthesis which at first do not produce oxygen. These organisms generate ATP by exploiting a proton gradient, a mechanism still used in virtually all organisms.
3000 Ma > Photosynthesizing cyanobacteria evolve; they use water as a reducing agent, thereby producing oxygen as waste product. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere slowly rises, acting as a poison for many bacteria. The Moon is still very close to Earth and causes tides 1,000 feet (305 m) high. The Earth is continually wracked by hurricane-force winds. These extreme mixing influences are thought to stimulate evolutionary processes.
2500 Ma – 542 Ma
2500 Ma > Great Oxidation Event led by Cyanobacteria's oxygenic photosynthesis. Commencement of plate tectonics with old marine crust dense enough to subduct.
2000 Ma > Diversification and expansion of acritarchs.
By 1850 Ma > Eukaryotic cells appear. Eukaryotes contain membrane-bound organelles with diverse functions, probably derived from prokaryotes engulfing each other via phagocytosis. The appearance of red beds show that an oxidising atmosphere had been produced. Incentives now favoured the spread of eukaryotic life.
1400 Ma > Great increase in stromatolite diversity.
By 1200 Ma > Sexual reproduction first appears, increasing the rate of evolution.
1200 Ma > Simple multicellular organisms evolve, mostly consisting of cell colonies of limited complexity. First multicellular red algae evolve
1100 Ma > Earliest dinoflagellates
1000 Ma > First vaucherian algae (ex: Palaeovaucheria)
750 Ma > First protozoa (ex: Melanocyrillium)
850–630 Ma > A global glaciation may have occurred. Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution.
580–542 Ma > The Ediacaran biota represent the first large, complex multicellular organisms - although their affinities remain a subject of debate.
580–500 Ma > Most modern phyla of animals begin to appear in the fossil record during the Cambrian explosion.
580–540 Ma > The accumulation of atmospheric oxygen allows the formation of an ozone layer.This blocks ultraviolet radiation, permitting the colonisation of the land.
560 Ma > Earliest fungi
550 Ma > First fossil evidence for ctenophora (comb-jellies), porifera (sponges), and anthozoa (corals & anemones)