Life Originally Arose via. Abiogenesis

What is lifeNote the definition I provided was:“Systems that can self-replicate and evolve via. natural selection”This is important because it is such a system which is proposed to continue rather automatically via. evolutionary processes established in the theory of evolution to produce the structures and diversity present in life today.Con contests this definition stating that a genome is required, which seems to be a fair objection. My arguments will argue for such a system to form, as good arguments can be made that a type of ‘genome’ is one of few ways within our current natural laws to proceed via. the cumulative, consistent autocatalytic processes which allow for sophisticated systems such as life today to emerge.As such, the elements of a genome which I will argue to be accessible via. abiogenesis will be one that possesses memory capability, template, and imperfect replication ability. All three of these capabilities lay the backbone of what is required of a genome which can undergo evolution via. natural selection.Note, this system is unlike even the simplest of cell systems that are extant today, and abiogenesis in this debate will not address their formation. However, such a system must necessarily be capable of producing life we have today.Thermodynamic InevitabilityBefore addressing the question of ‘did’ life form abiotically comes the question of ‘why’ did life form abiotically if it did. Is there a drive, or particular natural process which makes such a system favourable.The first consideration is that state of the early Earth if life never formed, what would the environment then have been like? The atmosphere was thick in cyanides, methane, carbon dioxide etc.[1] and bathed in concentrated UV and visible light these are all energy-dense, low entropy states, and hence under ‘thermodynamic stress’, it is always favourable for the system to move to a higher-entropy state (e.g. a UV light photon reemitted as multiple infrared photons). This is the driving force for every process that occurs in the universe, the entropy must overall tend to increase and hence states to achieve this are naturally explored.[2-4]Given this, the Earth without life was under significant ‘thermodynamic stress’, and this is where life comes in. Life is very good at ‘relieving’ this thermodynamic stress, it is hence thermodynamically driven. Much like the pressure exerted by a lake behind a hydroelectric dam is a ‘system that wants to tend towards equilibrium’, such is the state of the chemistry and energy on Earth. Anything that provides a pathway for a system to run down to equilibrium will be rapidly exploited and utilized by the system, which in the dam example could be a crack within the walls of the dam, and on Earth a new pathway for these molecules and photons to reach higher entropic states.[5]Autocatalytic Origin of LifeModel of LifeAt its most basic level, life can be modelled as a type of self-propagating process. Life takes in raw materials in the form of ‘food’, which the cell uses to create additional imperfect copies of itself. See the figure below: There are three key things one must note about this schematic: i. The ‘food’ sources are of low entropy ii. Total entropy of the environment increases at each stage via. heat release & mitosis iii. The system is autocatalytic, as the product itself can particulate in each cycle Because the system is autocatalytic, if all other factors are irrelevant then the system will continue to multiply at an exponential rate. This repeats itself over and over until you have 4,8,16,32 etc.. So long as there is food in the system, the cells will replicate indefinitely, and it is partially for this reason why life is so stubborn, since it constantly replaces itself at an exponential rate. Moreover life has the ability to evolve over generations which allows life to achieve versatility over a variety of conditions.AutocatalysisTo demonstrate how nature can produce such a system as life, first basic chemistry needs to be considered. In chemistry we like to stick things together, and addition-type chemical reactions are very common in synthetic chemistry and natural chemistry, one famous example is the synthesis of ammonia from nitrogen and hydrogen. This reaction is exothermic, yet does not readily occur at ambient conditions, despite having a thermodynamic drive to do so, even elevated conditions (high temperatures & pressures) only perform this reaction slowly. This and a great variety of reactions are enormously accelerated by introducing a catalyst that regenerates itself at the end of each cycle. In the Haber process, the rate of ammonia formation is accelerated to commercially profitable levels with the use of a metallic catalyst. Implementing a catalyst generally reduces the temperature and increases the rate of formation of the end product. This is accomplished by lowering the ‘activation barriers’ that prevented the chemical reactions occurring at room temperature (see figure below).[6] Such processes are rather life like, as life itself is essentially a type of ‘catalyst’, converting high energy molecules such as glucose and oxygen into lower energy molecules such as CO2 and water with an increase of entropy. The biggest difference is that they do not self-reproduce. A catalytic system such as this will inevitably ‘burn itself out’ due to catalyst poisoning without a source to regenerate the catalyst.Autocatalysis is a special case of catalysis where the product itself is identical to the catalyst (see figure below). We have the same thermodynamic drives to produce the product, but now the reaction is self-sustaining and self-accelerating! Any decreases in the concentration of catalyst, through loss or contamination, are negated by the new catalyst being produced at an increasing rate with each cycle. Moreover the reaction occurs at an ever accelerating rate as the catalyst that originally accelerated the reaction is present in ever higher quantities, effectively a ‘runaway reaction’.[6] Here we have a system that is very much life-like. It reproduces itself and is resistant to external effects. A good autocatalytic process will likely continue ad infinitum until the concentration of input reagents exhausts, which is never if there is a continuous source of these. Autocatalysis systems are well-known in chemistry and is close to a system that could be classified as rudimentary ‘life’.[6]These systems are already present in nature, in abundance. For life all we need is the same system that templates itself. The templating process is catalytic, as it would catalyse the formation of polymeric bonds (such as in DNA/RNA oligomer formation), and hence would be thermodynamically driven, and also would be autocatalytic, as the templating process also directs the formation of itself, moreover templates are not perfect, and hence have an adaptive mechanism available within it which allows for a cycle that can increase in sophistication with each cycle.This is very thermodynamically favourable, and any process that can accomplish these steps would very quickly become established and adaptive, and very conceivably lead to live as we know it today.There exist many OOL theories that can fill this step, the most heavily researched is the RNA-World hypothesis, largely due to its obvious abiotic fulfilment of the aforementioned templating process which would lead to an adaptive autocatalytic system, but there are many others.[7]Abiotic Synthesis of RNAI am not necessarily defending the RNA World hypothesis, as yet simpler base systems would work just as well, with RNA and by extension DNA being a later evolution. However, simple pyrimidine nucleotides have been synthesized under conditions thought to occur during the Early earth [8,9], these include the use of very plausible simple early earth feedstock molecules (many are released geothermal). The reaction is robust over differing pH conditions, which significantly reduces the amount of 'luck' required to make these nucleotides. Polynucleotide FormationGiven the nucleotide bases, oligomers and polymers are formed by the coupling of multiple monomers into a linear chain. These are known to form abiotically via. inorganic clays (the clay acting as a catalyst) which were likely present on the early Earth [14]. These chains are largely random in the order the amino acids are in.These RNA strange duplicate using nothing but heat, which was in abundance at the time due to the geology of the Earth at the time, and is a process frequently used today in the polymerase chain reaction (albeit with better catalysts) to amplify RNA strands. Furthermore, these RNA strands can fold on itself to form three dimensional structures, similar to the structures we see in proteins, and can perform many of the functions that protein enzymes perform today.What is interesting is that very long polymers and 'tarred' impurities, which is basically the 'gunk' you get if you heat a mixture of chemicals too hot and too long, these impurities naturally remain as a solid phase, and do not significantly pariticipate what occurs within the solution phase. [12-14]Ribozyme catalysisRibozymes of just 200 bp have been shown to be capable of the complete autocatalytic process I have described. Of course we have not addressed the search-space of all possible configurations of RNA that would be active in self-replication, but only a minor rate of activity is required to drive reproduction to self-sustaining levels. [10] Moreover ribozymes capable of replicating strands longer than itself and evolving have been demonstrated.[11]References 1. http://goo.gl... 2. http://goo.gl... 3. http://goo.gl... 4. http://goo.gl... 5. http://goo.gl... 6. http://goo.gl... 7. http://goo.gl... 8. http://goo.gl... 9. http://goo.gl... 10. http://goo.gl... 11. http://goo.gl... 12. http://goo.gl... 13. http://goo.gl... 14. http://goo.gl...