Abstract
What is necessary to elucidate the origin of life, is to make clear establishment process of the first genetic system composed of gene, tRNA (genetic code) and protein. Two ideas, RNA world hypothesis and [GADV]-protein world hypothesis or GADV hypothesis, have been proposed to elucidate the origin of life through making clear the establishment process of the genetic system. [GADV] or GADV means four amino acids; Gly [G], Ala [A], Asp [D] and Val [V]. In the RNA world hypothesis, it is considered that the genetic system was formed in order of gene, tRNA (genetic code) and protein along the flow of gene expression or in a “top-down manner”. Contrary to that, the GADV hypothesis is an idea that the genetic system was formed in order of protein, tRNA (genetic code) and gene as going against the flow of gene expression or in a “bottom-up manner”. It was investigated which one is valid for explaining formation process of the first genetic system. Consequently, it has been concluded that the origin of life cannot be made clear by the RNA world hypothesis or in the “top-down manner”. On the other hand, it has been confirmed that the process from chemical evolution to emergence of the first life can be reasonably explained according to the GADV hypothesis or in the “bottom-up manner”.