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Jens

Early Life! -- Life could only originate early or not at all

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This is an attempt to jointly (in this forum) sketch a most likely scenario for origin of life

 

 

----Start--of--Note-----------------------------------------------------------------------------------

Let’s jointly sketch a most likely scenario for the origin of life. Since the origin of life is a historic event, the target is not to prove anything but to achieve plausibility.

I am looking forward to your comments / critics / opinions smile.png

 

How to structure the discussion:

  • I have sketched a most likely scenario for the origin of life from my point of view as a starting point for the discussion.
  • Read the abstract provided below (in this first post)
  • Before you make a comment to a specific topic read the corresponding chapter (follow the links to the pdf document). It is only 2 pages per chapter.
  • Any critics, better ideas, supporting ideas are very welcome. I am very well willing to change my point of view.
  • In case the discussion is constructive, I will summarize and update the document by mentioning your user names as source of the corresponding change (of course only, if you agree)

Please do not:

  • Post any comments on how probable or improbable extraterrestrial life is -> use the speculative topic “Lonely Life? – Is Earth the only planet with life in our galaxy?” instead (it is in the same forum).
  • Claim that nothing can be proven, or nothing is known, or everything is pure speculation. (means you have not even read the 3rd sentence of this topic smile.png )
  • Post critics without reading the detailed chapters. (I have no problems with critics, but if my only answer is either to include the complete detailed chapter in every answer, or answering that you should read it, the whole topic becomes unreadable for all the others.)

----End--of--Note-----------------------------------------------------------------------------------------

 

 

I try to show that life already evolved during the time of disastrous meteorite impacts which nearly sterilized the whole Earth by boiling and evaporating most of the liquid water. This is in contrast to the usual unquestioned assumption that early life evolved after the meteorite bombardment of early Earth calmed down and stable oceans were present.

The proposed scenario of origin of life

The proposed scenario of origin of life comprises the following steps:

  1. Early Start. Evolution of life did not start started after the meteorite bombardment of early Earth calmed done and stable oceans were present. In contrast it started right with the first presence of liquid water. The typically called hostile environment of early Earth indeed was not preventing the evolution of life but in contrast was absolutely necessary for evolution of life.
  2. Concentration. Heavy meteorite impact events literally boiled some of the oceans (on global scale) or water reservoirs (on regional or local scale). Additionally strong volcanic activities had the same effect on regional and local scale. Thereby all the organic precursor molecules present where concentrated and condensed to energy rich bigger molecules. Only very few life forms survived.
  3. Dilution. After the impact event the surface of the Earth cooled down again and liquid water again was present in big amounts. The remaining life forms benefit from an enormous amount of high energy condensed molecules. So after each event an extremely energy rich primal soup was available to the survivors.
  4. Evolution. Those few survivors had nearly no competition and therefore could undergo rapid evolution until the next event happens.

 

post-78233-0-50546200-1356100063_thumb.png

 

Steps 2 to 4 were repeated multiple times on local, regional and global scale. The following evolutional phases were made across multiple of those cycles above as shown in the Figure: a) RNA-based life forms (bound on rocks). b) The translation was invented initially with a very small set of amino acids. c) More and more amino acids were introduced in translation. There were multiple life forms present at the same time with different numbers of amino acids actually used. d) In a catastrophic global event only very few (preferentially thermophilic) life forms survived which had the genetic code as known today. Other life forms with less amino acids (or even more) or a different encoding did not survive. e) The few survivors with the homogeneous genetic code evolved further. The first living cells emerged only after this catastrophic global event by developing cell membrane biosynthesis as two independent ‘inventions’ for Bacteria and Archaea. {see page 1 in “Early Life”}

 

The main reasons for this thesis are:

  • The unexpected uniformity of the genetic code, which indicates either a near extinction event or extra-terrestrial origin of life or massive horizontal gene transfer.
    {see page 3 chapter “Details I: the unexpected uniformity of the genetic code”} The chapter Details I also contains a reasoning why horizontal gene transfer is less plausible as source for the uniformity of the genetic code.
  • The two fundamentally different forms of cell membranes, which indicate that life started on Earth and not on another planet.
    {see page 5 chapter “Details II: The two fundamentally different forms of cell membranes”}
  • The much bigger evolution speed needed to explain all the fundamental "inventions" which lead to the first living cells. Evolution always made great steps in short time when there was a large environment open to conquer without competition by other life forms already present. The temporary and nearly Earth-wide repetitive absence of competition (caused by the bombardment) is the most perfect environment you can think of to make giant steps in evolution.
    {see page 8 chapter “Details III: Evolution Speed”}
  • Local heat-caused concentration produces both polymers and high energy molecules to sustain primitive life forms with all kinds of building blocks after dilution.
    {see page 10 chapter “Details IV: The need for high energy molecules to start life”} The chapter Details IV also contains a reasoning why autotrophic origin of life as an autocatalytic chemical cycle is less plausible.
Edited by Jens

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I copied Moontanman's comment from the other topic because it belongs to this topic:

Thomas Gold speculated, somewhat controversially, that life is a naturally occurring chemical process that all nearly all planets develop at some point but generally becomes extinct as chemical processes change as the planet changes.


The real theory about life started as chemical process is coming from Wächtershäuser.
(you pointed me to Thomas Gold already, but there was not much content. However, if you like we can start the debate again.)
For example: Wächtershäuser G (1994) Life in a ligand sphere. Proc Natl Acad Sci U S A 91: 4283-4287. http://www.pnas.org/content/91/10/4283.short

Some argumentation against it is from L. Orgel who changed his mind at the end of his life (actually I found this very honorable. We have too little scientists who are willing to change their mind):
Orgel LE (2008) The Implausibility of Metabolic Cycles on the Prebiotic Earth. PLoS Biol 6(1): e.18
doi:10.1371/journal.pbio.0060018

Here my reasoning against autotrophic origin of life (for full reading see the pdf Early life what you see here is from chapter details IV page 11)

There are multiple issues with the autotrophic origin of life as proposed by Wächtershäuser:

  • The unfavorable thermodynamics of polymer formation in a diluted environment as discussed above.
  • One has already brought up by de Duve and Miller [43]: Any environment which allows for spontaneous polymerization near chemical equilibrium will simply randomize any sequence information (and kill life). RNA molecules with randomized sequence cannot be the start of life and further evolution.
  • But main issue with Wächtershäuser’s theory is that autocatalytic small molecules cannot evolve. Life begins where molecule or set of molecules is capable of making a copy of itself and can undergo changes to evolve. If the active catalyst does not change, the produced molecules will not change. But in the proposed theory the active catalyst is the pyrite surface and not the ‘auto-catalytic’ small molecule which is part of a metabolic cycle. This means after a very short time the system produces all the possible molecules and will not change any more. Of course, if the small input molecule change, the same pyrite surface catalyst can actually produce different output molecules. However, since the active catalyst does not change, the chemical reaction always stays the same and will not evolve. The whole system will reach the maximum of complexity very quick and not evolve further. To start evolution (and life) you need a system in which the active catalyst makes an error prone copy of itself and hence has the possibility to reach different three-dimensional forms and gain other catalytic capabilities. Only exact three-dimensional folding allows stabilizing unfavorable intermediate states to allow for specific catalysis. To overcome this issue Wächtershäuser has introduced the concept of ligand feedback [40]. This concept postulates that some of the produced small substances bind to the surface as ligands and change the catalytic behavior of the pyrite surface, which in turn produces more complex metabolic cycles and more complex ligands. However, also with this assumption there is a fundamental issue: The ligand will win which bind strongest no matter which autocatalytic features it has. And this can and will happen at any point in time of the supposed evolution of the pilot metabolism. This is especially true in an environment with constant flow of water (as the assumed environment in Wächtershäuser’s theory). An autotrophic metabolic cycle in a constant flow environment will not evolve to biological complexity but rather will quickly reach a local optimum and not evolve further (if there is any evolution at all).
  • Another issue is that the theory assumes initial evolution of life at very high temperatures. To overcome this there was the assumption that initially there is another form of macro­molecules which is more stable than RNA at high temperature. If there is really a form of “RNA” which is more stable in heat and simpler than usual RNA and if life really originated in hyperthermophilic environment, why are modern hyperthermophilic organisms not using it anymore? In addition there are some special adaptations to heat especially the higher GC content and reverse gyrase [44] which also indicate that hyperthermophily is not the default environment of life. In contrast to usual topoisomerase I which is just relaxing negative supercoils (without consuming ATP) caused by unwinding of the DNA during replication, reverse gyrase is actively (by consuming ATP) introducing positive supercoils into DNA to prevent unwinding of DNA at high temperatures. It is present both in hyperthermophilic Archaea and hyperthermophilic Bacteria. If life really originated in an hyperthermophilic environment, instead of changing GC content from the statistical distribution you rather expect an original set of the bases which all form 3 hydrogen bonds (so for example 2,6-diaminopurine instead of adenine).

The final issue is explained by Orgel [45]: The existing and proposed autocatalytic metabolic cycles for autothrophy can only work if every single step has only very few irreversible side reactions talking material out of the cycle. This finally requires a high specificity of the mineral surface catalysts, which is nearly impossible to expect.


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Lets back this up just a small amount, there are other schools of thought about the origin of life. I've skimmed through your links and while I cannot critique them I do know that they are not the last word.

 

 

 

The final issue is explained by Orgel [45]: The existing and proposed autocatalytic metabolic cycles for autothrophy can only work if every single step has only very few irreversible side reactions talking material out of the cycle. This finally requires a high specificity of the mineral surface catalysts, which is nearly impossible to expect.

 

 

I don't understand this statement, when you have an entire planet full of various chemical cycles going on continuously with no doubt billions of reactions a second even the improbable becomes inevitable and RNA needn't be the first self replicating molecule.

 

Now this is my own personal opinion but I think the origin of life was a synergistic process where many cyclic chemical reactions, each producing something that other cycles used slowly formed both inside and outside bubbles of detergent like chemicals formed by wave action. These bubbles of chemical reactions combined and were torn apart many times before the ability to divide came about.

 

I have a couple pretty good videos on file that explain parts of these processes but the idea that suddenly a cell formed and was able to reproduce due to a complex chemical like RNA was almost certainly way down the line from the first actual reproducing chemical systems...

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Lets back this up just a small amount, there are other schools of thought about the origin of life. I've skimmed through your links and while I cannot critique them I do know that they are not the last word.

Of course I am not claiming to have the last word. However, a self-replicating molecule first (RNA or something similar to it) is still what the majority of scientists currently prefer above the low molecular chemical cycle first (metabolism first) school of thoughts. This is no argument of course, but should be known as context of the discussion: see e.g. RNA worlds.

I don't understand this statement, when you have an entire planet full of various chemical cycles going on continuously with no doubt billions of reactions a second even the improbable becomes inevitable and RNA needn't be the first self replicating molecule.

What is stated by Wächtershäuser is that there was a stable "autocatalytic" cycle of low molecular substances (in a stable steady state environment like in current deep sea black smokers) and not a random chaotic environment. There is a claim by Wächtershäuser that this chemical cycle slowly evolves into more complexity. Note that this cycle is autotrophic (independent from organic molecules) right from the beginning. Orgel (after supporting this theory initially) shows the mentioned severe issues with this.

 

There is no detailed theory of how life could start with chemical cycles (and without self-replicating large catalytic molecules) in a chaotic (unstable) environment. If you know one, please provide a link.

 

I agree that RNA does not need to be first molecule. But I agree with the current majority that a self replicating macromolecule able to do catalysis was in the beginning and not a metabolic cycle of multiple low molecular substances.

 

I will answer to the rest of your post also (just have to leave now)...

Edited by Jens

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Of course I am not claiming to have the last word. However, a self-replicating molecule first (RNA or something similar to it) is still what the majority of scientists currently prefer above the low molecular chemical cycle first (metabolism first) school of thoughts. This is no argument of course, but should be known as context of the discussion: see e.g. RNA worlds.

What is stated by Wächtershäuser is that there was a stable "autocatalytic" cycle of low molecular substances (in a stable steady state environment like in current deep sea black smokers) and not a random chaotic environment. There is a claim by Wächtershäuser that this chemical cycle slowly evolves into more complexity. Note that this cycle is autotrophic (independent from organic molecules) right from the beginning. Orgel (after supporting this theory initially) shows the mentioned severe issues with this.

 

There is no detailed theory of how life could start with chemical cycles (and without self-replicating large catalytic molecules) in a chaotic (unstable) environment. If you know one, please provide a link.

 

I agree that RNA does not need to be first molecule. But I agree with the current majority that a self replicating macromolecule able to do catalysis was in the beginning and not a metabolic cycle of multiple low molecular substances.

 

I will answer to the rest of your post also (just have to leave now)...

 

 

Try this video

 

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Try this video

 

The video provided is fine for schools (if you stay at that high level).

It also explains in a good way the current status of know-how to non-scientists and addresses in a simple way a lot of "critics" raised by religous fundementalists and I wish you all the best with the battle against creationists (I like your statement "You do not possess belief, belief possesses you...").

 

But this is not a discussion in this topic.

 

My topic here addresses scientists or people with good biochemical understanding (final university level). Your video rightly stated "It has to be said that this research is in its infancy and current hypothesis are no where near as solid as the theory of evolution..." I am drilling into these details here and my proposal is much further than the video.

 

By the way:

- The chemical formulars in the video contain some errors (at 0:33, 1:38, 2:17)

- RNA does not attract the hydrophopic part of membrane lipids. RNA is completely hydrophilic and cannot bind to the hydrophobic part of a membrane lipid as shown in the video. The shown cell does not work.

- The video seems to imply the order RNA -> DNA -> Protein, which no scientist is claiming. In fact the only open debate is about if RNA replication and protein biosynthesis evolved jointly and initially or one after the other. DNA is nothing more like a tape storing information which was introduced rather late in origin of life (and surely after protein biosynthesis).

- The video stated "One of the differences of RNA and DNA is that DNA needs proteins to replicate itself" and implies further that this is the main reason why protein is needed. Sorry but that is completely misleading (or to put it frankly: simply wrong). Today both RNA and DNA need proteins to replicate. The main difference between RNA and DNA is that RNA can act as an active catalyst and DNA not (discovery of this was a nobel price, if I emember correctly). This is because RNA (unlike DNA) can form precise and nearly arbitrary three-dimensional structures (depending on its sequence of bases). So the obvious speculation is in the past RNA could be replicating itself (which DNA could never do). ...and this is not my personal view but simply the current status of discussions in the scientific community....

 

I am willing to help to improve such videos in detail (if you know the authors, of course I would help to change it to the current main stream opinion in science and not to my personal one which I present here). It is nevertheless a good video.

 

Just another example: The whole basic sense (let alone the more advanced features like electrochemical gradients) of a membrane is to keep the concentration of water soluble intermediates inside the cell different than outside (in order to allow longer chemical pathways e.g. for synthesis of the biomolecules or to activate the nucleotids to replicate RNA). However, if a membrane is able to do this, nothing from the outside can enter any more, especially the highly polar molecules the RNA is made of. And even worse: RNA is completely incabable to create hydrophobic surfaces needed for transmembrane carriers. You need protein for it. This means most likely evolution already started before first membranes where established (since otherwise you have to assume that a complete cell with RNA, primitive ribosomes, primitive adapters, tons of enzymes, carrier proteins and a membrane sponteneously was formed, which is nonsense. Or you find better other alternatives like Wächtershäuser's theory).

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If you have information that disagrees with potholer54 you should indeed inform him of that, it would not be the first time he has accepted new information and he is always gracious when corrected. I have completely lost tract of what you want to discuss here. How about in as few words as possible tell us what you want to assert here.

 

Your title seems to indicate you want to say that life can and only form early in a planets existence. I would agree with that assertion. If you want to discuss how life formed then we both have many degrees of freedom to wave our arms since there is very little empirical data.

 

Personally i think life forms quite easily, it's formation so soon after water became stable on the earth's surface would seem to indicate that. I do understand there are other schools of though on this but I was unaware that only Wächtershäuser's theory was valid.

 

You start out saying you want to discuss possibilities, I assert that synergistic effects of many processes resulted in life as we know it, metabolism first...

 

You appear to only want to support Wächtershäuser's theory, which I do think is very interesting and almost certainly is an important part of how life formed, or perhaps even why. The following video is a bit less simple than potholer54's video was, relevant data starts at about 02:40 I would genuinely like to discuss the possibilities with some one who's agenda is not proving evolution to be wrong, this is a very deep subject, I did not intend for potholer54's video to be the whole story or even most of it but simply to indicate that there are many possibilities which worked together to form life as we know it. I have no doubt there many intermediate steps some of which are no longer part of life.

 

I "think" that the early earth was not only awash with complex organics, details of their possible origin would no doubt fill many books, but these molecules were locked in complex cycles that made other cycles possible and may have even inhibited others. I have read of so many different possible ways that these chemical cycles imitated the basic chemical processes that occur in cells today, no doubt chemosynthesis and photosynthesis were already present well before the first cell formed.

 

My own personal opinion is that a process similar in some says to symbiosis resulted in these chemical cycles establishing themselves in close proximity to each other feeding off the results of each from building larger molecules out of smaller ones to taking these molecules and making complex organic polymers that interacted with others in or near an energy gradient that drove the entire process.

 

No doubt there were several of these interdependent processes that were included in the first aggregates of chemical cycles that eventually formed structures that could be called simple self replicating self regulating self sustaining "cells" I am not sure they would be recognized as life as we know it now but they would have been the beginning of life.

 

In the interest of honesty I have to inform you that i do not meet the requirements you set forth to be qualified to discuss this.

 

 

 

My topic here addresses scientists or people with good biochemical understanding (final university level)

 

If you will forgive my the obvious leaning of my explanations toward trying to explain this to Creationist types, i will attempt remember that I am not debating if it happened but how it happened...

 

Again, this is a simplified description of a few of the processes that might have been involved, relevant data starts at about 02:40

 

 

Again i will say that my assertion trimmed to it's most basic level is that prebiotic chemistry went through several if not many steps that most resembled the evolutionary process of symbiosis rather than a great many different avenues to life that competed with each other directly for resources...

 

Even evolution can be said to have been driven by symbiosis, eukaryotic cells, the basis of all known complex life attest to this...

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I have completely lost tract of what you want to discuss here. How about in as few words as possible tell us what you want to assert here.

 

Your title seems to indicate you want to say that life can and only form early in a planets existence. I would agree with that assertion. If you want to discuss how life formed then we both have many degrees of freedom to wave our arms since there is very little empirical data.

Usually (in all books about this topic) it is assumed that life has emerged after stable oceans have been formed.

I claim here:

- that life has formed already during meteorite bombardment when no stable oceans where present yet.

- that life is not coming from another planet.

- that life could only emerge under the repeting dilution concentration conditions during meteorite bombardment. This means life had to emerge early or not at all.

- ... and I explain why other explanations are less plausible

 

 

 

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Usually (in all books about this topic) it is assumed that life has emerged after stable oceans have been formed.

I claim here:

- that life has formed already during meteorite bombardment when no stable oceans where present yet.

- that life is not coming from another planet.

- that life could only emerge under the repeting dilution concentration conditions during meteorite bombardment. This means life had to emerge early or not at all.

- ... and I explain why other explanations are less plausible

 

 

 

 

Actually this doesn't seem to be a completely unsupportable assertion. I hesitate to say it is the only mechanism that originated life but it's a reasonable idea... I wonder how you get to the idea that meteorite bombardment is going to just evaporate the oceans and not evaporate the chemicals left behind, like salts for instance. You seem to be basing this on the idea that the bombardment was just enough each time to not destroy any biological compounds but intense enough to evaporate all the water... seems like a tiny window of opportunity ..

 

The effects of such bombardment could range from the earth having a silicon dioxide vapor atmosphere to a small tsunami. Can you support that most impacts were of the just the right size?

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Again, this is a simplified description of a few of the processes that might have been involved, relevant data starts at about 02:40

 

Unfortunately the video cannot bee viewed in Germany (because of the music).

But I will try to get it anyway.

I Found the PPT form already:

http://www.mediafire.com/?jfijmimctnd

 

The following link seems to work (but there is no speaker -- only music. I assume that is correct)

http://www.mediafire.com/?yyd0eywkmhj

 

(Again I am not questioning abiogenesis.)

 

I will comment the PPT:

- I agree to everything from slide 1-54

- slide 50: "The pre-biotic environment contained hundreds of types of different nucleotides (not just DNA and RNA)." However, there is currently no reason for having one set of nucleotides and one set of bases in one chemically created polymer. So the "1 to self polymerize" is actually very hard to obtain. Since it should distinguish between the different monomers provided (at least not use those which do not allow for proper base pairing at all).

- slide 51: "Recent experiments have shown that some of these are capable of spontaneous polymerization, such as phosphoramidate DNA" But even the authors agree, that we do not expect such high energy molecules in nature in the quantity needed (they react with other stuff before). ... and DNA was not there in the beginning (However, but the lack of one OH group in DNA is needed as otherwise you do not obtain a stable structure). Even Szostack is not claiming that this is the solution. It just shows that sponteneous polymerization is possble in principle (in high concentration and clean solutions ....).

- slide 56: "Our fatty acid vesicles are permeable to nucleotide monomers, but not polymers". Yes. However the monomers cannot form polymers (nucleotid mono phosphates). What you need to form polymers are at least nucleotid diphosphates. They have multiple electrical charges and do not pass the proposed fatty acid membranes any more.

- slide 57, 58, 59: o.k.

- slide 60, 61: "Once the temperature cools spontaneous polymerization can occur. And the cycle repeats" I suppose here that in early earth before stable oceans where present, the cycling of heat and cold was much more common and not only at the (quite) rare hydrothermal vents. But mainly of course because the bombardment and strong volcanic environment was constantly concentrating and diluting chemicals which is a source of enrgy rich moelcules of all kinds (much more than you ever find in hydrothermal vents).

- slide 69: "Early genomes were completely random and therefore contained NO information." The main issue here is that without specific autocatalysis (by a specific 3D structure determined by a non-random sequence of bases) there is no way to specifically incorporate the right molecules to obtain a polymer chain at all. And not just random chaos network-like macromolecule, which is a mixture of everything available in the environment -- not even base pairing in any reproducable way. However but the base pairing is the prerequisite that evolution can start. So even though the proposal in this slide deck looks good at a first glance it is not plausible from my point of view. I think it is much more plausible to assume a real autocatalytic polymer in the beginning and the specific incorporation comes with the catalytic activity.

 

Or in a summary:

Current energy rich monomers have too many charges to pass even an early fatty acid membrane.

Theoretical other monomers and polymers with less charges are so energy rich that they will just produce chaos (and not a polymer chain) if available in a natural environment and not in a clean solution in the laboratory.

 

So I doubt the follwing statements in this video

- I doubt that the first polymers are without a specific sequence but doing base pairing (this does not seem to be possible)

- Hydrothermal vents do not provide those energy rich monomers today. It is better to assume beginning of life during meteorite bombardment to provide the energy rich molecules

 

And maybe the importance of the membranes is overestimated. Actually in the model proposed they are of no use to help polymer formation at all (quite the contrary). It is just that we are used to think life in form of cells. Life could very well started as an autocatalytic molecule without membrane first.

 

 

...and thanks again for the link to the video. (I have the underlying article as reference [5] in my document "lonely life") but I was not aware of the video.

Edited by Jens

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This is speculation.

That was clearly stated in the OP...

 

I think I have a few comments to make, but I still have to do more literature searching. Also, I am not that well read on this topic.

 

I'm not totally sure how the reverse citric acid cycle was relevant in Orgel's essay, does the prebiotic Earth have to use the same intermediates in the cycle? There have been reports of viable metabolic pathways, which can produce pyruvate, acetate, succinate and other compunds from a more simple cycle. http://www.ncbi.nlm.nih.gov/pubmed/19968461.

 

But main issue with Wächtershäuser’s theory is that autocatalytic small molecules cannot evolve. Life begins where molecule or set of molecules is capable of making a copy of itself and can undergo changes to evolve. If the active catalyst does not change, the produced molecules will not change. But in the proposed theory the active catalyst is the pyrite surface and not the ‘auto-catalytic’ small molecule which is part of a metabolic cycle. This means after a very short time the system produces all the possible molecules and will not change any more. Of course, if the small input molecule change, the same pyrite surface catalyst can actually produce different output molecules. However, since the active catalyst does not change, the chemical reaction always stays the same and will not evolve. The whole system will reach the maximum of complexity very quick and not evolve further. To start evolution (and life) you need a system in which the active catalyst makes an error prone copy of itself and hence has the possibility to reach different three-dimensional forms and gain other catalytic capabilities. Only exact three-dimensional folding allows stabilizing unfavorable intermediate states to allow for specific catalysis. To overcome this issue Wächtershäuser has introduced the concept of ligand feedback [40]. This concept postulates that some of the produced small substances bind to the surface as ligands and change the catalytic behavior of the pyrite surface, which in turn produces more complex metabolic cycles and more complex ligands. However, also with this assumption there is a fundamental issue: The ligand will win which bind strongest no matter which autocatalytic features it has. And this can and will happen at any point in time of the supposed evolution of the pilot metabolism. This is especially true in an environment with constant flow of water (as the assumed environment in Wächtershäuser’s theory). An autotrophic metabolic cycle in a constant flow environment will not evolve to biological complexity but rather will quickly reach a local optimum and not evolve further (if there is any evolution at all).

Does a metabolic cycle have to evolve? The metabolism first theory could mean that the metabolic events allowed for life to arise? like providing energy and nucleotides? no?

 

ne has already brought up by de Duve and Miller [43]: Any environment which allows for spontaneous polymerization near chemical equilibrium will simply randomize any sequence information (and kill life). RNA molecules with randomized sequence cannot be the start of life and further evolution.

I think this view has been challenged and it might not be as likely as once thought. In vitro selection experiments from random RNA have been able to create vital catalytic functions such as ligation, replication, translation. Since you stated self-replication, there is a paragraph (in the first link) on self-replication where it provides some basic experimental evidence.

http://onlinelibrary.wiley.com/doi/10.1002/cbdv.200790055/pdf

http://www.ncbi.nlm.nih.gov/pubmed/18775793

 

My opinion is somewhat similar to moontanman's opinion, that metabolic cycles came before RNA. As for the first cells, there are differing ideas out there, lipid, detergent, and a different type of cell from the iron-sulphur world theory (can't remember what it was, FeS bubble?). I still have a lot to learn on this topic however.

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I didn't create this topic since I am not the same person as the original poster.

 

I don't give out negative rep often, but I felt this one was deserved. "This is speculation" was totally unnecessary because the original poster already stressed that point and said that she didn't want that kind of response. So how exactly does his post contribute? is it the usage of italics?

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Sure abiogenesis is trying to figure out how biochemical complex molecules arose from nothing to build a biochemical vehicle however where do our thoughts fit into the equation?

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Sure abiogenesis is trying to figure out how biochemical complex molecules arose from nothing

 

No, this is not close to accurate...

 

to build a biochemical vehicle however where do our thoughts fit into the equation?

 

Our thoughts do not fit into this equation at all...

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No, this is not close to accurate...

 

 

Our thoughts do not fit into this equation at all...

 

You're right. I got confused with the title.

 

Correction: Sure abiogenesis is trying to figure out how atoms come together to form complex biochemical molecules, enzymes, and cells to build a biochemical vehicle however where do our thoughts fit into the equation?

 

Why aren't our thoughts into the equation? They(thoughts) aren't part of the picture?

Edited by Consistency

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First of all: sorry I am really late in answering (was too much occupied by the other thread). I will answer all your comments.

Does a metabolic cycle have to evolve? The metabolism first theory could mean that the metabolic events allowed for life to arise? like providing energy and nucleotides? no?

No.

I agree with you: I think those cycles could really have played a role in producing more homogenous molecules as source for life. And initial life could have replaced the steps one by one. But the metabolism first theory really assumes that those cycles become more and more complex by themselve and become life at a certain point in time. This is what I (and not only me, it is the default view) argue against. (The metabolism first try to show that life is inevitable.)

 

Why aren't our thoughts into the equation? They(thoughts) aren't part of the picture?

This is not part of this topic. Not because I am afraid talking about it, but it is really a separate topic (you are free to open up a new topic).

 

I think I have a few comments to make, but I still have to do more literature searching.

I am looking forward to discuss them with you.

 

 

{I have written:...has already brought up by de Duve and Miller [43]: Any environment which allows for spontaneous polymerization near chemical equilibrium will simply randomize any sequence information (and kill life). RNA molecules with randomized sequence cannot be the start of life and further evolution.}

I think this view has been challenged and it might not be as likely as once thought. In vitro selection experiments from random RNA have been able to create vital catalytic functions such as ligation, replication, translation. Since you stated self-replication, there is a paragraph (in the first link) on self-replication where it provides some basic experimental evidence.

I fully agree with what you have written.

However, the argument from de Duve (and I agree) was a purely thermodynamical one. Wächtershäuser claimed that conditions on the surface (via binding the polymer to charged mineral surfaces) could change in a way that polymerization could happen spontaneously near chemical equilibrium (remember that the metabolism first theory assumes life is autotrophic right from the beginning). So ultimately the chemical cycles really produce RNA (and not the RNA was produced by something else and is using the metabolic cycles). However polymerizing and hydrolyzing near chemical equilibrium will destroy any specific sequence of RNA nucleotides.

 

This is speculation.

 

Please read my full text (as mentioned above): http://www.jfreund.de/dateien/early_life_short.pdf

I have put quite a bit literature research in it (see all the references) and it is not more speculation than what others publish in those scientific papers.

The speculation part I have separated in another topic. (in the same forum, currently rated as "hot" :) ).

 

To avoid any misunderstandings:

I have a scientific education, worked as scientist and I do not have any believes. Especially I do not think any power has created life on Earth. And this topic is not to discuss such things.

 

I really mean this as a scientific disussion.

 

So any hint why you think it is not even worth discussing is appreciated and I will answer (However, you should read it first.)

 

!

Moderator Note

Then perhaps you should have posted this in Speculations, which is where this is now being moved to.

 

This is a misunderstanding. I will clarify (I have send you a message).

This topic is really meant seriously and is based on more than 50 scientific articles (see references in the link in the original post).

Edited by Jens

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The tite of this topic seems to be confusing.

Within the next two weeks I will post this as a new topic with the question I want to discuss as title.

 

greetings, Jens

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