An Interpretive Review of the Origin of Life Research |
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Authors: | David Penny |
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Institution: | (1) Allan Wilson Center for Molecular Ecology and Evolution, Massey University, Palmerston North, New Zealand |
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Abstract: | Life appears to be a natural property of matter, but the problem of its origin only arose after early scientists refuted continuous
spontaneous generation. There is no chance of life arising ‘all at once’, we need the standard scientific incremental explanation
with large numbers of small steps, an approach used in both physical and evolutionary sciences. The necessity for considering
both theoretical and experimental approaches is emphasized. After describing basic principles that are available (including
the Darwin-Eigen cycle), the search for origins is considered under four main themes. These are the RNA-world hypothesis;
potential intermediates between an RNA-world and a modern world via the evolution of protein synthesis and then of DNA; possible alternatives to an RNA-world; and finally the earliest stages
from the simple prebiotic systems to RNA. The triplicase/proto-ribosome theory for the origin of the ribosome is discussed
where triples of nucleotides are added to a replicating RNA, with the origin of a triplet code well-before protein synthesis
begins. The length of the code is suggested to arise from the early development of a ratchet mechanism that overcomes the
problem of continued processivity of an RNA-based RNA-polymerase. It is probable that there were precursor stages to RNA with
simpler sugars, or just two nucleotides, but we do not yet know of any better alternatives to RNA that were likely to arise
naturally. For prebiotic stages (before RNA) a flow-reactor model is suggested to solve metabolism, energy gradients, and
compartmentation simultaneously – thus the intense interest in some form of flow reactor. If an autocatalytic cycle could
arise in such a system we would be major steps ahead. The most likely physical conditions for the origin of life require further
clarification and it is still unclear whether the origin of life is more of an entropy (information) problem (and therefore
high temperatures would be detrimental), rather than a kinetic problem (where high temperatures may be advantageous). |
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Keywords: | origin of life RNA world origin of the ribosome Darwin-Eigen cycle flow reactor |
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