Mixtures of Nutrients and Cofactors evolved into Metabolic Networks consisting of GADV-Proteins, PAHs and subsequently Peptide-RNA polymers or RNA only . These polymers evolved within Montmorillonite Clay, Iron-Sulfur, and /or Zinc precipitated environments on hydrothermal vents within proto-earth , planetismals, or inside cosmic spherules . It is unclear if the Polymer worlds evolved from a metabolism first , replicon first and/or hybrid network .
RNA based life most likely evolved prior to DNA based life. Nucleobases for RNA/DNA include purines (ie, adenine, inosine, and guanine ) that hydrogen bond with pyrimidines ( cytosine, thymine, and uracil ) and polymerize with ribose or other precursors to form ProtoRNA strand and hairpin loops . Deamination of adenine with NO (Nitric Oxide bubbled up from Dissolved Iron reacting with Water and Nitrous Oxide) produces inosine while deamination of cytosine with NO produces uracil . Gas bubbles created the first protocells containing concentrated concentrations of nucleobases within lipid membranes micells.
Current evidence exists for the presence of life on Earth 4.2 Billion years ago. There are also theoretical calculations which propose that the Last universal common ancestor of cellular life (LUCA) had DNA sequences which would require an origin of the genetic code to have been 9.7 ± 2.7 billion years ago. (longer than the existence of earth)
Cellular Life responds to destructive forces (physical and biological) by activating mobile genetic elements to create protective /defensive proteins and RNA. Mobile Genetic Elements are agents of Darwinian variation and they interact with hosts, infectious predators and cosmic-climatic-geochemical events. Continuous interaction promotes consortia development between mobile elements and their hosts resulting in the evolution of complex organisms and ecosystems. Koonin’s model views these forces as being driven by parasite/anti defense systems or the availability of resources “public goods”.