ABSTRACT
The scientific evidences suggest that the planet Earth appeared about 4.6 billion years ago following a cosmic event of unimaginable proportions. This planet was initially a blob, in which, in due time, elements predominantly of the lower atomic weights — hydrogen and helium — appeared; the atmosphere was without oxygen. The original surface of the Earth may have been too hot for water to remain liquid, but as soon as the temperature had fallen the boiling point, water, released from the interior by outgassing processes, such as volcanism, would have condensed to form the original oceans. During this chemical evolution it is generally believed that all of the molecules essential for life were successively synthesized. Starting with pure inorganic compounds, a set of inorganic-organic reactions took place leading to the building stones for proteins and nucleic acids; these are amino acids and nucleotides. A living cell has two central talents: a capacity for metabolism and a capacity for reproduction.
