The major hypotheses on the origin of life are (1) RNA world hypothesis and (2) Protein world hypothesis. Many questions on the origin of life remain to be solved as OQOL2009 (Open Questions on the Origins of Life 2009) proposed. International Workshop on OQOL2009 was held in Spain, in May, to answer the questions. Although I could not attend the meeting, I tried to answer the questions raised by OQOL2009.
The RNA world hypothesis, which is becoming a most popular hypothesis, has been extensively evaluated in the last two decays. However, this hypothesis has some drawbacks. First, the hypothesis that life originated near hydrothermal vent environments (the hydrothermal origin-of-life hypothesis) appears to be inconsistent with the RNA world hypothesis. In our group, the thermal stability, the chemical evolution, and the behaviors on RNA molecules under hydrothermal conditions were systematically investigated using our monitoring methods for rapid hydrothermal reactions. Based on these empirical data, the RNA world hypothesis is discussed from the viewpoint of the hydrothermal origin-of-life hypothesis and different plausible RNA world systems are proposed. Second, the reality of the RNA world in detail is still ambiguous. Thus, several plausible RNA worlds are evaluated as life-like systems on the basis of the unified theory regarding the origin-of-life and evolution of organisms, which was recently established in our group.
A new theory of evolution is discussed: the energy-surplus theory of evolution. The fundamental question in evolution is why the normal processes of development patterns of various organisms have been determined as they are. Based on our experimental works on development of starfish, we have reached the theory emphasizing the role of energy, available in excess of minimal necessity for survival, and simultaneously reached a new view about life and origin of life, or ecological world; the RICH world in life. We are now directly measuring the thermal power in organisms. Any living individual is under energy balance, and has to consume energy so as to continue its metabolism, and it has to gain energy at least corresponding to the amount of energy loss for further continuation of the metabolism. Life is such contradictory dynamic state. Therefore, living organisms are constantly forced to keep the energy balance non-negative (zero or positive), or to accumulate surplus energy as a whole for the continuation. The surplus energy makes individuals endurable and adaptable under severer environmental conditions. Important viewpoint about life is as follows: on selection, that what is favorable and what is injurious varies depending on life styles just adopted by species. Therefore, phenotypic changes of forms or metabolisms precede the DNA reorganization among various mutations, and directions of diversification are not necessarily dichotomous. Dr. Tomoko Ohta says about evolution as follows: "Since 'the nearly neutral theory' has gotten general agreement, then next step is to connect phenotypic evolution with molecular (DNA) changes." According to the energy-surplus theory we can answer Ohta's question as follows: 1) Since organisms have surplus energy that depends on premise of life, DNA changes with slight injuriousness can be kept in individuals, 2) Phenotypic changes in species in step always precede DNA changes (mutations): these DNA reorganizations follow phenotypic changes so as to make the species life style stable, and, 3) Since large DNA changes can only be possible in DNA areas responsible for non-functional components, it is necessary to consider that any DNA area with large changes had been functionless or weakly functional at the time of the happening of the changes (mutations). Thus, through our own experiments with echinoderms, we have obtained deeper understandings of "the present" of living organisms, and "Why the present has come?" "The present" includes indispensably non-necessary (useless, degenerating, surplus) components because of premise of life. Any present function has not been aimed from the beginning. The larger the amount of surplus becomes (the larger the bodies becomes), the more rapidly the evolution in organisms progresses because of increase of possibility.
それに対して，私たちは生命はGly [G], Ala [A], Asp [D]そして，Val [V]の4種のアミノ酸からなるタンパク質で構成された[GADV]-タンパク質ワールドから生まれたとの[GADV]-タンパク質ワールド仮説，略して，GADV仮説を提案している．