28 A. P. VINOGRADOV 



same tendency is found, to a certain extent, in the temperature of the surface 

 of the Earth. I would suggest that the peculiarity of the time when the Archaean 

 biosphere came into existence was just this considerable amount of heat at the 

 surface of the Earth. It manifested itself in numerous volcanic and post- volcanic 

 phenomena in the form of hot gases, hot springs and so forth. This could have 

 led to intensive catalytic synthesis of numerous organic substances on the surface 

 of the Earth from CO2, CO, HaS, S, NH4, CH4, HCl, HP and other 

 compounds on a scale which has been unparalleled since that time. From the 

 time of the inception of the biosphere to the Cambrian period, in the strata of 

 which palaeontologists have found highly organized organisms including all 

 forms of invertebrate animals, at least 1-5 -2-0 x lo^ years must have elapsed. 

 In the course of this time there must obviously have developed all sorts of methods 

 of oxidation of H2S and other analogous processes and, later, the dehydrogenation 

 of H2O by means of chloroplasts as well as other reactions. Any conceivable 

 process of photodissociation of H2O would have taken lo^ years to form the 

 oxygen of the atmosphere. The photosynthetic O2 in the atmosphere is produced 

 during 5000 years, forming a sound basis for the development of aerobic life. 

 Many other geochemical cycles of elements and molecules in which organisms 

 were an essential link were also set up and consolidated. Thus, the phosphates 

 of the bones later provided a basis for the development of the neuromuscular 

 tissue in vertebrates. Many other molecules were drawn into these cycles and 

 became involved in the evolution of organisms. CaCOa, CaHP02, chitin, cellulose, 

 porphyrins and many other, even more complicated compounds were among 

 them. This, however, is a long way outside the province of the geochemical 

 history of the biosphere. 



Thus, we may conclude that the mechanism by which the Ught basaltic for- 

 mations were melted out from the whole thickness of the mantle of the Earth 

 under the influence of radiogenic heat, was associated with the outgassing of 

 H2O, CO2 and other gases and vapours on to the surface of the Earth. This 

 determined the composition of the primary Archaean atmosphere and ocean. 

 In the course of time the composition of the salts of the ocean and that of the 

 atmosphere may have undergone some change owing to the irregular accession 

 of vapours and gases to the surface of the Earth. The Archaean atmosphere 

 contained, among other vapours and gases, NH4CI, H2S and S of abiogenic 

 origin and, possibly also CH4 and some O2, which provided the necessary con- 

 ditions for the catalytic synthesis of complicated organic compounds if the 

 temperature was raised. The last marked changes in the composition of the 

 oceans and atmosphere took place between 3x10^ and 2 x lo^ years ago when 

 the temperature of the surface of the Earth became much what it now is. The 

 ancient nuclei of the continents persisted and provide evidence of magmatic 

 phenomena which took place in the remote past, being locally completed 3 x lo^ 

 years ago. We have no reason to exclude the possibihty of the existence of 

 anaerobic forms of life at that time. At the same time as, or sUghtly later than the 

 alteration in the geosyncHnal condition of the surface of the Earth there appeared 

 the first platform-hke structures which were submerged in the shallow seas. 

 These seas were associated with the intensive precipitation of CaCOa and the 



