Abstract:Thermodynamic stability, as expressed by the Second Law, generally constitutes the driving force for chemical assembly processes. Yet, somehow, within the living world most self-organisation processes appear to challenge this fundamental rule. Even though the Second Law remains an inescapable constraint, under energy-fuelled, far-from-equilibrium conditions, populations of chemical systems capable of exponential growth can manifest another kind of stability, dynamic kinetic stability (DKS). It is this stabilit… Show more
“…Some researchers claim that a chemical environment held in a non-equilibrium state by kinetic barriers constitutes a prerequisite for the development of very specific dynamic chemical systems of constituents and catalysts capable of circumventing these kinetic barriers. They support the concept of the dynamic kinetic stability, DKS [ 42 – 44 ]. According to these authors, the stability kind is the stability associated with entities able to make copies of them at a rate that results in a non-equilibrium steady-state population of replicating entities being maintained over time.…”
“…Hence, it is questionable to claim there is a true reproduction because, as in Wächtershäuser’s model, the system does not multiply. In addition A. Pross and R. Pascal say nothing about heredity [ 42 – 44 ]. Finally, R. Pascal admits that no practical example has yet been identified of an autocatalytic network capable of both reproducing itself, fed by light energy, and carrying information in a way possibly leading to selection and accumulation of genetic information [ 43 ].…”
BackgroundThis essay highlights critical aspects of the plausibility of pre-Darwinian evolution. It is based on a critical review of some better-known open, far-from-equilibrium system-based scenarios supposed to explain processes that took place before Darwinian evolution had emerged and that resulted in the origin of the first systems capable of Darwinian evolution. The researchers’ responses to eight crucial questions are reviewed. The majority of the researchers claim that there would have been an evolutionary continuity between chemistry and “biology”. A key question is how did this evolution begin before Darwinian evolution had begun? In other words the question is whether pre-Darwinian evolution is plausible.ResultsStrengths and weaknesses of the reviewed scenarios are presented. They are distinguished between metabolism-first, replicator-first and combined metabolism-replicator models. The metabolism-first scenarios show major issues, the worst concerns heredity and chirality. Although the replicator-first scenarios answer the heredity question they have their own problems, notably chirality. Among the reviewed combined metabolism-replicator models, one shows the fewest issues. In particular, it seems to answer the chiral question, and eventually implies Darwinian evolution from the very beginning. Its main hypothesis needs to be validated with experimental data.ConclusionFrom this critical review it is that the concept of “pre-Darwinian evolution” appears questionable, in particular because it is unlikely if not impossible that any evolution in complexity over time may work without multiplication and heritability allowing the emergence of genetically and ecologically diverse lineages on which natural selection may operate. Only Darwinian evolution could have led to such an evolution. Thus, Pre-Darwinian evolution is not plausible according to the author. Surely, the answer to the question posed in the title is a prerequisite to the understanding of the origin of Darwinian evolution.ReviewersThis article was reviewed by Purificacion Lopez-Garcia, Anthony Poole, Doron Lancet, and Thomas Dandekar.
“…Some researchers claim that a chemical environment held in a non-equilibrium state by kinetic barriers constitutes a prerequisite for the development of very specific dynamic chemical systems of constituents and catalysts capable of circumventing these kinetic barriers. They support the concept of the dynamic kinetic stability, DKS [ 42 – 44 ]. According to these authors, the stability kind is the stability associated with entities able to make copies of them at a rate that results in a non-equilibrium steady-state population of replicating entities being maintained over time.…”
“…Hence, it is questionable to claim there is a true reproduction because, as in Wächtershäuser’s model, the system does not multiply. In addition A. Pross and R. Pascal say nothing about heredity [ 42 – 44 ]. Finally, R. Pascal admits that no practical example has yet been identified of an autocatalytic network capable of both reproducing itself, fed by light energy, and carrying information in a way possibly leading to selection and accumulation of genetic information [ 43 ].…”
BackgroundThis essay highlights critical aspects of the plausibility of pre-Darwinian evolution. It is based on a critical review of some better-known open, far-from-equilibrium system-based scenarios supposed to explain processes that took place before Darwinian evolution had emerged and that resulted in the origin of the first systems capable of Darwinian evolution. The researchers’ responses to eight crucial questions are reviewed. The majority of the researchers claim that there would have been an evolutionary continuity between chemistry and “biology”. A key question is how did this evolution begin before Darwinian evolution had begun? In other words the question is whether pre-Darwinian evolution is plausible.ResultsStrengths and weaknesses of the reviewed scenarios are presented. They are distinguished between metabolism-first, replicator-first and combined metabolism-replicator models. The metabolism-first scenarios show major issues, the worst concerns heredity and chirality. Although the replicator-first scenarios answer the heredity question they have their own problems, notably chirality. Among the reviewed combined metabolism-replicator models, one shows the fewest issues. In particular, it seems to answer the chiral question, and eventually implies Darwinian evolution from the very beginning. Its main hypothesis needs to be validated with experimental data.ConclusionFrom this critical review it is that the concept of “pre-Darwinian evolution” appears questionable, in particular because it is unlikely if not impossible that any evolution in complexity over time may work without multiplication and heritability allowing the emergence of genetically and ecologically diverse lineages on which natural selection may operate. Only Darwinian evolution could have led to such an evolution. Thus, Pre-Darwinian evolution is not plausible according to the author. Surely, the answer to the question posed in the title is a prerequisite to the understanding of the origin of Darwinian evolution.ReviewersThis article was reviewed by Purificacion Lopez-Garcia, Anthony Poole, Doron Lancet, and Thomas Dandekar.
“…It is perhaps not overly optimistic to imagine that soon it will be possible to catch a glimpse, if only on the distant horizon, of an answer to the question of how simple matter becomes complex 43 . This will likely involve a replication mechanism 74,75 , and insight into the effects of kinetic asymmetry 15,16 , allostery 76,77 , escapement and disequilibria 78,79 , and dynamic kinetic stabilization 41,42 will have a critical role in designing such systems.…”
Section: Resultsmentioning
confidence: 99%
“…In the limit that the chemical potential difference between substrate and product is large, . Recently, Pascal and Pross 41,42 have based an approach for describing the onset of complexity in terms of the amplification of kinetic asymmetry by replication, terming the adaptive behavior “dynamic kinetic stabilization” and offering insight into how simple matter can self-organize to become complex 43 through catalysis with kinetic asymmetry.Fig. 5Catalysis-driven information ratchet can undergo non-equilibrium adaptation.…”
Molecular machines carry out their function by equilibrium mechanical motions in environments that are far from thermodynamic equilibrium. The mechanically equilibrated character of the trajectories of the macromolecule has allowed development of a powerful theoretical description, reminiscent of Onsager’s trajectory thermodynamics, that is based on the principle of microscopic reversibility. Unlike the situation at thermodynamic equilibrium, kinetic parameters play a dominant role in determining steady-state concentrations away from thermodynamic equilibrium, and kinetic asymmetry provides a mechanism by which chemical free-energy released by catalysis can drive directed motion, molecular adaptation, and self-assembly. Several examples drawn from the recent literature, including a catenane-based chemically driven molecular rotor and a synthetic molecular assembler or pump, are discussed.
“…However, through research in a relatively new area of chemistry termed systems chemistry [ 12 ], it has become increasingly clear that certain physical-chemical systems can be stable for kinetic , rather than thermodynamic reasons [ 13 , 14 ]. The persistent state that is achieved can be classified as one of dynamic kinetic stability (DKS) [ 15 , 16 , 17 , 18 ], as opposed to the more common stability kind, thermodynamic stability. Physical examples of dynamic kinetic stability are familiar—a water fountain or a waterfall.…”
The central thesis of the modern scientific revolution is that nature is objective. Yet, somehow, out of that objective reality, projective systems emerged—cognitive and purposeful. More remarkably, through nature’s objective laws, chemical systems emerged and evolved to take advantage of those laws. Even more inexplicably, nature uncovered those laws twice—once unconsciously, once consciously. Accordingly, one could rephrase the origin of life question as follows: how was nature able to become self-aware and discover its own laws? What is the law of nature that enabled nature to discover its own laws? Addressing these challenging questions in physical-chemical terms may be possible through the newly emergent field of systems chemistry.
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