Four geological facts help us to mark the Earth life development calendar.

(1) On Pibara craton on Australia west has been isolated zirconium silicate crystals eroded by liquid water, dated by its thorium and uranium content, with antiquity of 4.400 million of years.

This first fact, show us that only 100 million of years after Earth formation, exist a first plates of terrestrial crusts (cratons), whose minerals were eroded by liquid water.

(2) In Isua area, Greenland south-east, has been studied metasedimentary rocks, with a 3.800 million of years antiquity, that contain fossils. These fossil registers had a C12/C13 relationship and contain kerogens.

This second fact, indicates the seas existence (metasedimentary rocks are metamorphic rocks formed by marine sediments or lacustrine) where lived beings capable of forming organic carbon compounds (mineral carbonates have a relation between c12/C13 of 88.89 lower, to organic carbon compounds that is 90.2 higher)  and kerogens presence is a sign of this synthetic activity.

These living beings are the oldest line of known beings until nowadays that evolved in non-oxygen atmosphere.

(3) In Warrawoona, Australia west, has been found fossil registers in sediments with a 3.450 million years antiquity and a relation of C12/C13 higher to 90.2.

These fossil registers are better preserved than Isua, as it has not been subject to any metamorphic effort.

This third fact shows that living beings synthesizing activity of organic carbon compounds, extended their area of colonization in distant parts of the world but always in aqueous medium.

 (4) With a history of 3100 years have been found in many areas of the Earth, sedimentary rocks rich in iron oxide.

This last fact indicates that from 3800 million years ago to 3,100 million years there was enough oxygen in nature as to cause precipitation of metallic iron in the form of sediments containing iron oxide.

In conclusion we can say, according to current fossil record, that during the period between 4,500 and 4,400 million years the first plates of the earth's crust (cratons) formed, which between 4400 and 3800 million years mass formed liquid water on the surface of the Earth, 3,800 million years ago there were living beings with the capacity to synthesize organic carbon compounds extended their activity over 700 million years to large areas of the planet and produced by photosynthetic activity of organic compounds carbon (form of stored energy) and liberated oxygen atmosphere seas and in sufficient quantity to precipitate the metallic iron.

The next question is about the nature of living beings that could develop this activity. Considering that other living beings from currently primitive structure, that perform similar functions, we can say that those living beings were prokaryotes provided of circular DNA lacking a single membrane and organelles except internal ribosome. About them we will discuss in the next chapter as they constitute the beginning of the presence on Earth, "preplant" cells producing organic carbon compounds that store energy and with them the possibility of the presence of "preanimales" consuming cells opens the stored energy.