IMPACT, RNA-PROTEIN WORLD, AND THE ENDOPREBIOTIC ORIGIN OF LIFE
Life probably arose in a sequence of four stages in hierarchical fashion: cosmic, geological, chemical, and biological. In vent communities RNA and protein molecules emerged simultaneously and were encapsulated. The dual origin of ‘RNA/protein world’ is more parsimonious than the widely embraced ‘RNA world’ from the constraints of hydrothermal vent environments and the phylogeny of ribosomes. In this scenario, membranes came first to encapsulate simple RNA and protein molecules from mineral surfaces, where they began to perform two critical functions within protocells, replication and metabolism respectively. Once the membranes encapsulated these simple RNA and protein molecules, they began to interact and initiate serial endoprebiosis, leading to hierarchical emergence of cell components including plasma membrane, ribosome, retrovirus, and finally DNA with the development of the genetic code. Replication is the key breakthrough in the emergence of life. The hot subsurface environment of the crater basin, the oldest ecosystem, was suitable for the emergence of thermophilic life. RNA viruses and prions may represent molecular relics of the prebiotic world that predated the appearance of first cells.