Figure 7.

Evolutionary steps from the formation of Earth to the emergence of life, deduced from the bottom-up approach and GADV hypothesis (the top-down approach). Periods of physical-chemical, biochemical, and biological processes are shown by dotted, broken, and solid arrows, respectively. A juncture (the establishment of GNC primeval genetic code), which is used to determine the evolutionary steps that are consistent between the bottom-up and the top-down approaches, is indicated by bold italic letters.