Those consortia of replicators that were able to couple useful syntheses with
exergonic chemical reactions could have became relatively independent of upper,
photosynthesizing layers and could penetrate the depths of their porous habitats.
This penetration can be considered the first wave of the Earth’s colonization by
living organisms that eventually evolved from replicating zymes. This colonization
would have been supported by exchanges of metabolites between the illuminated
strata and those that were deeper and darker. In the darkness, direct contact
between the RNA-like “bodies” of replicators and the radiation-absorbing ZnS
template was no longer crucial, so that the replicators could evolve into life forms
that were enclosed in protein envelopes resembling modern viruses [62,70,219].